Current status of genetic information on Monterey pine
he genetic diversity information current- allozyme information on Monterey pine to be interpreted ly available for Monterey pine has been within an informed and comprehensive context. For some generated by four methodologies: ) com- genetic questions—particularly those of amount or structure mon-gardenT or provenance studies where diff erences in ob- of genetic diversity—some context is required for interpreta- servable traits (e.g., phenotypic traits such as growth rate or tion such as the area of the genome that has been sampled insect resistance) are inferred to have a genetic basis because and how genetic variability refl ected by the particular meth- of the constancy of the environment (e.g., fi eld or nursery od or marker varies across related taxa. Other questions, trial) in which the plants are growing; ) chemical composi- such as identifi cation of foreign pollen or domestic cultivars, tion studies, such as turpentine analysis; ) allozyme stud- have a more restricted context for interpretation. ies; and ) molecular studies of DNA or RNA. No matter which method has been used, there is much more informa- Phenotypic diversity tion on genetic diff erencesamong the fi v eve populations populations than than on genetic diversity within them. An additional source of Phenotypic diversity—refl ecting genetic and environmen- information comes from descriptions of the pines in situ. Al- tal infl uences and their interaction—is noted in early de- though phenotypic descriptions of trees in their native con- scriptions of Monterey pine. Considerable morphological text do not necessarily refl ect genetically based traits, a brief diversity exists within Monterey pine, suggesting to some review of some phenotypic diff erences among the native early taxonomists that these diff erences represented distinct populations is presented because these early observations species. One notable distinction between the island and provided clues about genetic diff erences which were often mainland populations is the grouping of needles—generally substantiated with subsequent genetic tests. grouped in fascicles of threes in the mainland trees and of Diff erent kinds of genetic information (or inferred ge- twos in the island trees. e Cedros Island population, for netic information) are appropriate for diff erent issues or example, was at one time called Pinus muricata D. DonDon or P. questions. For example, relationships between Monterey muricata var.var. cedroensis J.T.J.T. HHowellowell (M ). Another pine and other pine species (phylogeny) are perhaps better characteristic with much variation within the species is cone addressed by molecular and biochemical data than by mor- morphology. Variation among populations is strikingly evi- phological data (e.g., W and G ; W dent in average cone size (Figure ). ese diff erences have et al. ; S and D ; K et al. suggested several hypotheses. Population diff erences in cone ; F et al. ). Diff erent DNA markers have dif- size, cone symmetry, thickness of scales, and size and weight ferential strengths and weaknesses for the range of genetic of seeds suggested that these characteristics are related to cli- questions. Microsatellite markers have proven useful in iden- mate, and the length of the summer dry season in particular tifying among- and within-population genetic structure of (AA ). e diff erences among populations in the forest tree species (e.g., E et al. ; S et al. ); thickness of cone scales, cone attachment angles, and cone allozyme data continue to be useful in revealing levels of symmetry were suggested to be related to selective pressures genetic diversity and genetic structure within and between from fi re and squirrel predation L( ). populations. e great wealth of allozyme data for many L () found the Cambria population to be dis- forest tree species, particularly western conifers, allows the tinguished from the other mainland populations in its larger 21 average cone size, faster height growth, better stem form, studies—that could diff erentiate between genetic and envi- and tendency for foliage to be massed on the upper side of ronmental eff ects—confi rmed the existence of among-popu- the side branches, giving a terraced appearance to the trees. lation diff erences in needle length and the observation that Considerable information is available on diff erences in the Cambrian population has the longest needles. However, needle and branch characteristics within and among the some disparities were noted between these results and the three mainland populations, based on trees directly sampled earlier fi eld study. Specifi cally, the Monterey population was from the populations (F b,c). Briefl y, these studies found to have longer needles than the Año Nuevo popula- showed that trees in the Cambria population, as compared tion, and there were no signifi cant diff erences among popu- with those in the Monterey population, have signifi cantly lations in weight/length ratio of fascicles, indicating no pop- longer and thicker needles with more widely spaced sto- ulation diff erences in needle thickness—in contrast to the matal rows and marginal teeth. Trees from the Año Nuevo fi ndings of the earlier fi eld studyB ( and L ). population are intermediate in these characteristics with the Diff erentiation among populations of Monterey pine exception of the last characteristic: marginal teeth on needles is also suggested by the geology and soils. Underlying the of Año Nuevo and Monterey trees are signifi cantly more coastal California populations are diff erent geologic sub- narrowly spaced than on Cambria trees. Common-garden strates or soils that seem to confer some competitive advan- tage to the conifers over adjacent oak forests. e soils tend to be droughty or nutritionally poor. e unique sub- strates emphasize the fact that these populations represent island-like eco- systems, not just populations of trees (B ).
Common-garden or prov- enance studies Common-garden studies were estab- lished decades ago, many of them in Australia and New Zealand, and have since off ered information on genetic diversity of many traits. ere is evi- dence for substantial genetic diff er- ences among the fi ve Monterey pine populations in their resistance to western gall rust, a disease caused by the fungus Endocronartium harknes- sii (O et al. ). Specifi cally, the Guadalupe and Cedros Island popula- tions are least susceptible. Of the three mainland populations, Año Nuevo is the most resistant. e island popula- tions also are less susceptible to red band needle blight (C and L ). In glasshouse and fi eld studies in Australia, considerable genetic varia- tion in resistance to Phytophthora cin- namomi has been found both among and within populations of Monterey pine. Seedlings from the Cambria and Monterey populations showed the greatest degree of resistance. Seedlings from Año Nuevo and the two island populations generally were more Figure . Diversity in cone size among the fi ve native populations of Monterey susceptible (B et al. ; pine (AA , used by permission from University of California Press). Each B and S ). Also, cone represents the average size for that population. Key: Cedros Island; Guada- there was large variation within the lupe Island; Monterey; Año Nuevo; Cambria. Monterey, Año Nuevo, and Guada- 22 lupe Island populations in family-level resistance (B were noted among the samples from the Cambria popula- and S ). tion but only three areas there were sampled. ese results A California common-garden study containing clonal were explained as adaptations within subpopulations—the and seedling material from each of the three mainland pop- coastal areas at Año Nuevo and Monterey experiencing low- ulations showed that the Año Nuevo population suff ered the er temperatures, lower evaporation, more frequent fog drip, least cold damage following an unusually cold -day period and less salt accumulation within the soil profi le than in in December, ; the Cambria population showed the areas further inland (C et al. ). Common-gardenCommon-garden most damage; and the Monterey population had interme- studies in New Zealand show signifi cant diff erences among diate damage (H and L ). SubsequentSubsequent studies fi ve selected subpopulations of the Año Nuevo population have provided similar observations (AA and D- in height growth (measured at . and years), diameter, ; B et al. a). and incidence of forking (B et al. a). In this same e same common-garden study was also assessed for study, genetic diff erences in branching pattern were noted damage from black-tailed deer and porcupines—possibly a among subpopulations of the Monterey population, and in refl ection of genetic diff erences in palatability. Signifi cant -year height growth among subpopulations of the Cambria diff erences in damage were seen among the three popula- population. In this common-garden study, subpopulations tions: the least porcupine damage was on trees from the were artifi cial groupings of sampled trees, based on locality, Monterey population and the least deer damage (based on and hence may not have a clearly elucidated spatial genetic percentage of trees browsed) was to those from the Cambria structure within populations. A series of eight provenance population (H and L ). trials in New South Wales, Australia revealed signifi cant Common-garden studies in New Zealand have been height or basal area diff erences among some subpopula- conducted since the s, with signifi cant new tests added tions within the three mainland populations (J et in the mid-s and . is long-term series allows in- al. ). Also, as noted above, there were considerable dif- sights into genetic diff erences of the populations expressed ferences found within the populations (i.e., family-level) of in a nonnative environment. In general, these studies suggest Monterey, Año Nuevo, and Guadalupe Island in resistance that the Año Nuevo and Monterey populations are better to Phytophthora cinnamomi (B and S ). suited than the others to overall New Zealand conditions, Genetic diff erences among families (i.e., open-pollinated with the caveat that Año Nuevo is much less adapted to progeny from the same female parent tree) have been noted phosphorus-defi cient clay soils and better adapted to cold, for some seed and germination characteristics within the Ce- snow-prone sites. In these same studies, the Cambria popu- dros Island population (Q V. ). lation has shown susceptibility to two foliage pathogens (Dothistroma pini and Cyclaneusma minus), shoot dieback, Chemical analyses and frost and snow damage, but considerable tolerance to Additional genetic information comes from studies of tur- poor soils, and, in a Western Australian study, tolerance to pentine composition (e.g., B et al. ; B- Phytophthora cinnamomi. Trees from the Guadalupe Island and MD ) and seed protein (e.g., M population show modest overall adaptation to plantation ) diff erences among the populations of Monterey pine. conditions in New Zealand but have very straight stems and For both types of traits, considerable genetic diversity has higher corewood density than the others. Similarly, trees been noted. from the Cedros Island population show less overall adapta- An early study of the turpentine composition of cortical tion to these conditions than the mainland populations but oleoresin collected directly from trees of the three mainland interpopulation hybrids perform much better (B et populations showed diff erences in the proportion ofalpha - al. a,b, ). e higher wood density of the Guadal- pinene. Monterey and Cambria were quite similar in this upe Island population was also noted in a study in Austra- feature, and diff erent from the Año Nuevo sample B-( lia—where island populations were noted to have higher et al. ). However,However, because the trtreesees wwereere sampled wood density and thinner bark than mainland populations directly from the forest, the results could not be strictly in- (N and E ). A summary of genetically terpreted as genetic diff erences. In a later study, turpentine based diff erences among populations as observed in these composition from samples from the two island populations trials in New Zealand (with some supplementary informa- showed diff erences between the two populations, as well tion from other trials) is contained in Table . Note that the as considerable diff erentiation from the mainland popula- actual values for various populations (e.g., height superior- tions (B and MD ). However, again, ity of one population versus another) are site dependent environmental eff ects could not be ruled out. More recently, and thus may change were the trials to be located elsewhere. B et al. (d) provided more direct evidence of ge- However, the fact of underlying genetic diff erences remains. netic diff erences in turpentine composition among popu- ere are fewer reports of within-population genetic lations with samples from planted trees in New Zealand diversity but some of these show signifi cant genetic diff er- fi eld trials. In a comparison of Guadalupe Island material ences among subpopulations. A physiological study suggests with that from the three mainland populations, clear dif- that, paradoxically, stands on coastal areas at Año Nuevo ferences were found among all populations in at least two and Monterey have a lower salt tolerance as compared with of the monoterpenes assayed. When all monoterpenes were inland stands in the same populations. No such diff erences considered simultaneously, populations were again shown 23 as distinct, and Cambria and Monterey appeared the least the high degree of genetic control of monoterpene composi- diff erent, consistent with the earlier () observation. In a tion in this species (B et al. c). separate substudy within the same report, Cedros and Gua- Seed proteins from samples from each of the fi ve Mon- dalupe samples were compared and strong diff erences were terey pine populations have been compared using immuno- noted between the two island populations (B et al. chemical assay techniques. Signifi cant antigenic diff erences d). Other studies have confi rmed, using clonal material, were noted between populations (M ). ese
Table . Summary of phenotypic characteristics of the native populations of Monterey pine in fi eld trials in New Zealand (B ). Symbols: + denotesdenotes ssuperiority;uperiority; – ddenotesenotes iinferiority;nferiority; denotes average; and • indicates no data were located.
Population Weight of Guadalupe Cedros Attribute evidence† Año Nuevo Monterey Cambria Island Island Growth rate a + + + – – – Ease of transplanting bc + – +(+) – – Resistance/tolerance to: Frost b + + + – ? – – Snow damage c + – • • Boron defi ciency b + + + – – – – Phosphorus defi ciency b – + + + + –? – – Dothistroma pini ab + + + + – – – – Cyclaneusma minus a + + + – – – – –? Diplodia pinea b + + + + – – – – – Phytophthora cinnamomi b – – + + + • • Endocronartium harknessii b + – – – + + + Pineus pini c + + – – – + Damage by mammals: Deer/rabbit browse bc – + Deer browse b – + • • Porcupines b + + – – — — Soil salinity bc + + + – – - Tree form: Overall a – – + + – – Stem straightness a – – + + + + Forking (lack): Early a – – + + + Later – + + – – Branch habit: Early a – – + + + Later – + + – – Butt straightness a – – – – + + + + + Wood properties: Basic density a – – – + + + + Compression wood (lack) c – + ? ? Grain spirality (lack) c – + + – ? †Key: a denotes a large body of solid experimental evidence (many sites); b denotes good experimental evidence but from limited num- ber of sites/pot trials; c denotes slender evidence; and two letters denote intermediate weights of evidence.
24 diff erences strongly correlate with cone-length diff erences is mid-range. As compared with other California closed- among populations. Also, these data suggest that the two is- cone pines (knobcone, Ht=., S and C land populations are more closely related to each other than ; bishop, Ht=., M ), it is high. to the mainland populations (M ). Expected heterozygosity (He) under Hardy-Weinberg equilibrium ranges from to approximately . for the Allozyme diversity pine species for which data are available for or more e tremendous amount of allozyme literature for plant spe- allozyme loci (L ). e modal value lies between cies indicates that pine species are among the most geneti- . and .. e He values from studies of Monterey pine cally diverse plants (e.g., H et al. ). Allozyme (., M et al. ; ., P and S ; studies may reasonably be interpreted as refl ecting relative ., M et al. ) showshow both that genetic estimates levels of whole genome variation (e.g., W and G can vary considerably depending on sampling design and ). Not atypically, diff erent statistics and diff erent studies that Monterey pine lies in the normal (modal) range for show somewhat diff erent patterns (Table ). For example, pine species generally. ese values suggest that most indi- depending on which statistic and which study are consid- viduals of Monterey pine are expected to be heterozygous at ered, the Monterey, Cambria, or Cedros population has the about to of their loci (not adjusting for population highest diversity. For most allozyme measures of genetic di- diff erences). versity, though, the Monterey population shows the highest genetic diversity. Molecular diversity Compared with other western conifers, the genetic di- Monterey pine has a fairly large genome of approximate- versity of Monterey pine, as measured by certain allozyme ly bp (S and D ). As comparedcompared with statistics, is modest to average (Table ). Overall genetic di- other pine species for which nuclear DNA content has been versity (N ), including monomorphic loci, is estimat- recorded, Monterey pine is average (M et al. ). ed as Ht=. (M et al. ). However, as compared For example, Monterey pine has considerably more nuclear with other western pine species, the within-species diversity DNA than pitch pine (Pinus rigida) but much less than sug- ar pine (P. lambertiana) (D ). Montery pine at . pg of nuclear DNA (M ) is intermediate to Table . Allozyme diversity for the native populations bishop pine (. pg, H et al. ) and knobcone pine of Monterey pine from three studies: number of trees (. pg, M ). sampled per population (N), mean number of alleles Many of the approaches for assessing diversity at the per locus (A), percent polymorphic† loci (P), and ex- DNA molecular level have been employed with Monterey pected heterozygosity (H ). e pine. ree of the most useful types of markers have been Population N A P He RAPDs (random amplifi ed polymorphic DNA markers), M et al. RFLPs (restriction fragment length polymorphism markers), and microsatellites (simple sequence repeat markers). Ge- Año Nuevo . . . netic linkage maps have been constructed for Monterey pine Monterey . . . using all three (D et al. , ). Cambria . . . RAPD markers have revealed somewhat higher genetic Guadalupe Island . . . diversity and stronger among-population diff erentiation than an analysis with allozyme markers carried out with the Cedros Island . . . same populations (W et al. ; Table ). In this study, M et al. only trees from Año Nuevo, Cambria, and Guadalupe Island Año Nuevo . . were included. Other studies of diff erent plant species sup- Monterey . . port the observation that RAPD data reveal more genetic diversity than allozyme data. is may result from several Cambria . . conditions (reviewed by A et al. ), including the Guadalupe Island . . reasoning that allozyme data refl ect only a very limited part Cedros Island . . of the plant genome and a part that may evolve more slowly P and S or be under stronger selection pressures than the genome at large (W et al. ). Año Nuevo . . . A study of microsatellite sequences confi rmed the fi nd- Monterey . . . ing that dinucleotide repeats are abundant in the Monterey Cambria . . . pine genome, albeit seemingly less frequent than has been reported for some other species (S and D ). †With the exception of data from Plessas and Strauss, the criterion of polymorphism is , meaning a locus must e reasonably high levels of heterozygosity found in two have a second allele with at least a frequency of for microsatellite loci provide a basis for developing a fi nger- that locus to be considered polymorphic. For the Plessas printing strategy for Monterey pine. and Strauss data, the criterion is , thus these data are No signifi cant chloroplast DNA diversity was found an underestimate relative to the other data in the table. among the populations (H et al. ). However, chlo- 25 roplast DNA in general is highly con- Table . Allozyme diversity in western conifer species native to California: mean served and thus may not be a sensitive number of alleles per locus (A), percent polymorphic† loci (P), and expected het- marker for distinguishing populations erozygosity (He). within species. Species A P He Reference Population genetic structure uja plicata . — — C Genetic structure—the pattern of dis- Pinus torreyana . — L and C tribution of genetic diversity within Cupressus macrocarpa . — C and among populations—is important in conservation planning because it de- P. muricata . . M fi nes the rate and spatial scale at which Sequoiadendron giganteum . — F and L populations can evolve in response to P. attenuata . † — W et al. environmental perturbations (P P. radiata . . MORAN et al. ). Genetic structure is, to a large extent, spatial structure. Most plant P. radiata‡ . — WU et al. populations have substantial spatial P. radiata — . MILLAR et al. structure—limitations in the distances Larix occidentalis . — J and E-K that individuals (or propagules) dis- perse will result in relatives mating due Chamæcyparis lawsoniana . — M and M to close proximity and consequently Taxus brevifolia . — W et al. the buildup of genetic isolation by dis- P. ponderosa§ — . N and C tance (e.g., E and L ). Calocedrus decurrens . — H Genetic structure (often measured P. albicaulis . — J and H with the statistic FST) is generally in- creased by local selection and genet- P. contorta . . C ic drift and decreased by gene fl ow. — . Y and Y W () derived an equation to express the opposing relationship be- P. lambertiana . . C tween gene fl ow and genetic drift F( ST Sequoia sempervirens . — R = 1⁄4Ne m + ). In this relationship, m is Pseudotsuga menziesii . — C the number of migrants per generation †With the exception of data for P. radiata fromfrom WWuu et al., the criterion of polymorphism is (a measure of gene fl ow) andNe is the , meaning a locus must have a second allele with at least a frequency of for that locus eff ective population size. It can be seen to be considered polymorphic. For the Wu et al. data, the criterion is , thus these data that even a low amount of gene fl ow are an underestimate relative to the other data in the table. would greatly reduce the divergence ‡Calculated from samples of Cambria, Guadalupe, and Año Nuevo populations only. among populations caused by genetic §P. ponderosa var.var. ponderosa. drift. However, this equation assumes that the populations are at equilib- rium—a condition not often satisfi ed in nature. Others netic diff erences among the populations of Monterey pine, have attempted to evaluate the relative historical infl uences many of which are not well (or at least, not easily) explained of gene fl ow and drift on regional population structure by by natural selection, but are more likely a result of founder comparing the relationship between genetic and geographic eff ects from repeated local extinctions and re-colonizations distances, with good success (e.g., H and T- (B et al. a). ese lessons caution us about infer- ). Genetic structure is often interpreted as a function of Table . Comparison of RAPD and allo zyme markers in a genetic and ecological processes including natural selection study based on three native populations of Monterey pine in local environments, mating system, geographic distribu- (Año Nuevo, Cambria, Guadalupe Island): mean number tion, seed dispersal mechanism (e.g., H et al. ), of alleles per locus (A), percent polymorphic† loci (P), ex- successional status, population size, and natural disturbance pected heterozygosity (H ), and among-population diff eren- regime of habitat. ese generalizations are supported by e tiation (G , N ) (W et al. ). population genetic theory (e.g., M ) and much al- ST lozyme literature (e.g., H and G ). However, Marker A P He GST a review of genetic structure studies across a range of plant Allozyme . . . species reveals many exceptions to expected genetic structure based on genecology, suggesting that genetic structure may RAPD . . . be more a refl ection of the contingencies of evolutionary his- † e criterion of polymorphism is , meaning a locus must have tory than ecology, life form, distribution, or breeding system a second allele with at least a frequency of for that locus to be (R ). is view is supported by a review of ge- considered polymorphic. 26 ring cause and eff ect relationships where only correlations Additional perspectives on genetic structure come from exist. Evolutionary history, geographic distributions, popu- studies of the cytoplasmic organelle genomes—mitochon- lation demographics, and their associated features must all drial and chloroplast DNA. We might expect studies based be considered to understand the basis for specifi c genetic on mitochondrial DNA (mtDNA) to show stronger dif- structures and then interpret this pattern for conservation ferentiation among populations possibly as a result of lower purposes. rates of sequence mutation, small eff ective population Genetic structure is often used as a means of identifying size, and limited gene fl ow for maternally inherited organ- unique populations for conservation attention. us, atten- elles (e.g., B ). Indeed,Indeed, a rrecentecent study of mtDNA tion is given to such measures as the proportion of total ge- among the Año Nuevo, Cambria, and Guadalupe Island netic variation that is due to among-population diff erences populations showed a strong level of population diff erentia- (GST, N ) and Nei’s genetic distance between individ- tion (GST = .) (W, J. et al. ). is was consider- ual populations and others within the species (e.g., J ably higher than a similar study conducted on Douglas-fi r and E-K ). (H et al. ). Furthermore, this estimate of popula- Genetic diff erentiation among populations of Monterey tion diff erentiation for Monterey pine may have been an pine (based on allozymes) has been estimated as . of the underestimate since the population that is apparently most total genetic diversity (M et al. )—a rather large strongly diff erentiated from the others—Cedros Island—was proportion compared with other western North American not included. pine species (Table ). In fact, the value of . for Mon- Fine-scale genetic structure, or genetic patterns within terey pine is among the highest values presented by H- populations of Monterey pine, has not been well studied. () for conifers or byby L () for pine species. e few available studies used few stratifi ed samples per Using Nei’s genetic distance measure, the Cedros Island population and thus did not comprehensively explore pos- population is most strongly diff erentiated from the others, sible structuring associated with local selection regimes (e.g., and the Monterey and Año Nuevo populations are most elevation, microclimate, and soil type). Strong local genetic similar to one another. Genetic isolation by distance is sug- structure associated with soil type has been noted in some gested (r=., P=.) if the Guadalupe Island population other pine species. For example, abrupt changes in genetic is excluded from the analysis (M et al. ). variation are known in bishop pine due to changes in soil ese interpretations are largely, but not completely, fertility (M ) and in ponderosaponderosa pine (Pinus ponder- mirrored by a similar allozyme study (M et al. ). osa) due to serpentine/nonserpentine soils (L ). Here, the fi ve populations were strongly diff erentiated ( Some common-garden studies have, though, shown diversity among populations) and the Cedros Island popula- considerable diff erentiation among subpopulations of the tion was found to be the most genetically distant from all natural populations. For example, signifi cant diff erences in others. However, the loci assayed in this studied suggested the incidence of stem forking among subpopulations were that Monterey and Cambria were the most closely related noted in a series of common-garden studies conducted in pair of mainland populations. Chile (J and B ). Strong local dif- ese studies underscore the distinctiveness of the island ferentiation based on monoterpene levels has been noted populations. Indeed, both have been given varietal names, within the Año Nuevo population (B et al. a). prior to most of the genetic studies, based on their substan- e reason for this diff erentiation has not been determined. tial morphological diff erences from the mainland popula- Some of the possible causes include local adaptation, genetic tions and each other (see Taxonomy section in Chapter ). contamination from planted nonlocal trees, introgression with nearby knobcone pine, founder eff ects, or a combina- tion of all of these. e study’s authors favor the founder ef- Table . Estimates of proportion of total genetic variation fect explanation. In this case, trees near the edge of the main among populations (PGV), based on allozyme data, in population could have experienced a more restricted pollen rangewide studies of western North American pine species. cloud than those at the core, leading to some genetic diff er- entiation over time (B et al. a). Species PGV Reference () Mating system eff ects Pinus albicaulis . J and H e mating system of plants usually refers to the level of P. longæva . H and H inbreeding and outcrossing. Monterey pine is largely out- crossing, typical of the genus. Given that neither spatial nor P. contorta . W and G temporal separation of the sexes is strong (e.g., placement of P. attenuata . M et al. male and female structures on the tree and timing of pollen P. jeff reyi . F and A shed and seed cone receptivity), that related trees tend to be P. monticola . S et al. clustered, and that self-incompatibility seems to be lacking in most species of pines, the level of outcrossing must be P. radiata . M et al. maintained by some other mechanisms. Partial self-sterility P. muricata . M et al. resulting from inbreeding depression may be a major part P. torreyana . L and C of the explanation for many pine species (L ). In- 27 breeding depression may be expected in pine species because Nursery and fi eld studies conducted in New Zealand, in of the high frequency of recessive lethal genes that are found which comparisons were made between artifi cially cross-pol- throughout the genus (L ). Of course, inbreeding linated and selfed progeny of Monterey pine, provided fur- depression can have a variety of expressions, not all of them ther evidence that selfi ng can be detrimental. Selfed progeny the result of poor self-fertility due to recessive lethals. e were generally slower growing, had more crooked stems, expression of deleterious but nonlethal genes can be mani- displayed less desirable branching habit, and were more sus- fest as low viability in off spring that result from self-fertiliza- ceptible to needle diseases as compared with the cross-polli- tion, for example (R.D. Burdon, pers. comm.). nated progeny (W ). A recent study suggests that the overall outcrossing rate More evidence of selection against selfed genotypes in for Monterey pine may actually be quite low relative to Monterey pine is apparent from a study that compared many other conifers. e overall rate estimated from sam- genotypes from embryos, seedlings, and more mature trees. ples from the fi ve populations was ., and for the island In this allozyme study, homozygosity (i.e., indicative of self- populations was even lower: . and .. e lower out- ing) is highest at the embryo stage, less at the sapling stage, crossing rates observed in the island samples could, in theo- and least in mature trees (P and S ). In ry, be a result of less outcross pollen reaching the seed cones another comparison of inbred (selfed) and outcrossed seed- or lower numbers of embryonic lethal equivalents relative to lings, the inbred genotypes grew only to as well as mainland populations (S et al. ). the outcrossed genotypes over an -year period (P ere is considerable evidence of inbreeding depression ). e eff ects of inbreeding on growth were measured in Monterey pine, from lowered seed viability, to slower over years in a fi eld study of pedigreed Monterey pine in growth rates among seedlings, to smaller heights and diam- Australia (W, H.X. et al. ). Outcrossed material was eters of more mature trees. For example, there is evidence of compared with full siblings, half-sib matings, and fi rst- and lower viability of selfed embryos relative to outcrossed—one second-generation selfs. Inbreeding depression was shown study showing approximately fi lled seed in self-polli- to be a dynamic process, being greatest at the initial stage of nated cones versus fi lled seed in open-pollinated cones stand development (four years), lessening for several years, (G and L ). e reduction in propor- and then increasing again with a secondary peak at the end tion of full seed after selfi ng is due to embryonic mortal- of the study ( years). In summary, in pines in general and ity, because conifers have no self-incompatibility system Monterey pine more specifi cally, there is a fairly high expect- (S ). However, the selfi ng eff ect shown in ed true genetic load—which would tend to lead to inbreed- that study is less dramatic than that found in some other ing depression and drive the species towards outcrossing. pine species. For example, viability is reduced from . Understanding the genetic basis of inbreeding depres- (open-pollinated) to . (self-pollinated) in piñon pine sion is important for appropriate conservation decisions. For (Pinus edulis) (reviewed(reviewed in L ). InIn a contrcontrolled-olled- Monterey pine, we do not know how many loci mutate to pollination study, there were signifi cantly fewer selfed seed- lethals. We do not know whether inbreeding depression is lings produced than expected. is could have been the due to a few highly deleterious alleles or a large number of result of either lowered fertilization success with self pollen less deleterious alleles. If the former, then the unfavorable or reduced survival of inbred embryos (M ). alleles could be quickly purged; if the latter, they could be- More recently, a single recessive lethal allele, associated with come fi xed in the population S( ). Under- the death of Monterey pine seedlings (progeny of selfi ng) standing the nature of the genetic load in Monterey pine, in their fi rst month after germination, has been identifi ed then, is critical to choosing the appropriate management (K et al. ). response for inbred populations and for managing risk in the others.
28
Status of conservation for Monterey pine
he range of genetic conservation activities safeguarding the opportunity to understand the web of eco- is traditionally divided into two basic ap- logical interactions similar to those under which Monterey proaches: in situ and ex situ methods. In pine evolved, there may be some valuable guidance for silvi- situ conservationT has been defi ned as the continuing main- cultural, breeding, and genetic engineering eff orts of those tenance of an existing, wild population within the commu- with interests in the commercial values of Monterey pine nity of which it forms a part, in the environment to which (e.g., T et al. ). WWithoutithout concurrconcurrentent conserconserva-va- it is adapted (P and H ). In situ genetic tion of the pine forest ecological community, adult plants conservation is conservation of genetic resources on site—in may be maintained for some time, but genetic diversity in the natural and original population, on the site formerly future generations may be compromised. A case in point is occupied by that population, or on the site where genetic the dawn redwood (Metasequoia glyptostroboides) in China, resources of a particular population developed their distinc- which has been protected as a species since the s but tive properties. us, this approach involves preserving not without the attendant protection of its habitat. As a result, only associated fl ora, fauna, and ecosystem processes but ongoing human activities have impacted regeneration such maintaining the populations within a dynamic environment that only mature trees—perhaps the last generation—re- in which the genetic variation can continue to respond to main (B ). natural infl uences.Ex situ conservation refers to the suite of e focus of this report is on in situ genetic conserva- activities that involve removing genetic material from the tion. However, given that a comprehensive and eff ective natural populations and maintaining it outside of the natu- genetic conservation program should embrace both types ral habitat in such conditions as seed banks, clone banks, of conservation methods, ex situ conservation will also be seed orchards, or plantations. Both types of conservation reviewed and considered—to the extent that it enhances are dynamic—the genetic resources change over time—but the goals of in situ genetic conservation. at latter caveat diff er in the degree and infl uences of change.In situ genetic is important: given the tremendous and historical economic conservation favors genetic changes that are related to natu- importance of Monterey pine, there are many genetic col- ral selection and regeneration. Genetic changes in ex situ re- lections of Monterey pine worldwide, in various life forms serves may be more artifi cial (e.g., loss of seed viability over and degrees of separation from the original collections. A time in seed banks, artifi cial selection in nurseries). Howev- comprehensive review of all of these reserves is far beyond er, this distinction is not absolute. For example, a plantation the scope or intent of this report. Many, perhaps most, of that is allowed to regenerate naturally could be considered these collections would have little or no value to in situ con- an ex situ reserve yet still respond to natural selection. servation goals. e treatment of ex situ conservation in this A critical feature of the in situ approach is the conser- report will be limited to those collections that could play a vation of those associated populations and species, those supportive role in in situ conservation or restoration. natural disturbances, and those underlying processes that Ex situ genetic collections are an important parallel con- work to maintain genetic structure and diversity within a servation activity to the conservation of natural populations normal range of variation. Not only is an understanding of in situ. Ex situ collections can play a variety of roles includ- these coevolved organisms and processes important to the ing conservation support, research, education, and com- eff ective genetic conservation of the target species, but, by mercial applications. To play a meaningful support role for 29 in situ conservation, however, genetic collections should tegrity. For example, nonlocal Monterey pine trees, plant- represent the genetic diversity within the species or target ed outside of but close to a reserve, can still be a source of populations, maintain the genetic diversity (e.g., seed life) genetic contamination to the in situ reserves. Some forms over long periods of time, and be accompanied by strategies of recreation may also be incompatible with conservation for using such collections to establish self-sustaining popula- objectives. In most reserves, the natural processes control- tions under natural conditions (e.g., G and P ling the ecosystem’s composition and structure may not be ). restorable if degradation has proceeded too far (C Individually, ex situ reserves are ephemeral and vulner- ). Data from South Africa on the pressures causing ex- able to loss. Some ex situ genetic resources of Monterey pine tinction or threatening the survival of a species indicate that have been lost due to lack of funding (e.g., Guadalupe Is- even after creating a reserve, over half of the threats are likely land nursery, L et al. ; Monterey pine collections at to continue (H et al. ). Equivalent data from Aus- the University of California, L ). OthersOthers havhavee been tralia suggest that about half of threats are likely to continue reduced or lost due to more natural disasters. after reserve status has been conferred (L et al. ). Many weaknesses in relying on ex situ collections for ge- Accordingly, genetic reserves must be selected with genetic netic conservation have been cited. A major problem is the diversity and structure, ecosystem health, and restoration lack of knowledge about how to sample genetic diversity ap- potential in mind. propriately—how it is distributed within the population and Averaged over four native populations, approximately what alleles may be useful in future and uncertain environ- of the extant Monterey pine area has some kind of pro- ments. It has been suggested that there are declining incre- tected status. is fi gure excludes Guadalupe Island because ments of genetic variation collected for increasing sample of the few trees there and diffi culty in converting this to size. However, under neutral theory, any allele no matter area. ese protected areas are not evenly distributed over how rare may become evolutionarily signifi cant H( the native populations. For example, the pine population ). Some types of rare alleles may confer large fi tness ad- on Cedros Island has no specifi c protection. In contrast, vantages under conditions of frequency-dependent selection the California populations each have some protected area (e.g., H and G ). us, the sampling that ranges from approximately to perhaps of their design and intensity required to represent adequately the total respective pine forest area. However, there is no stan- genetic diversity of a species have not been convincingly es- dard here for ‘protected area’ and hence little comparability tablished. among populations for this value. Some protected areas are In situ conservation is critical: it cannot be replaced with simply narrow greenbelt areas or small parks, or highly de- ex situ conservation activities. e purpose of in situ conser- veloped or degraded areas that conserve few genetic values. vation is to maintain the evolutionary genetic adaptability of Guadalupe Island has protected status but there are grave populations and species over many generations (K et al. problems there with invasive exotic species—both plant and ). is approach is the only means of achieving both ge- animal. Similarly, some areas that currently do not have pro- netic conservation objectives: maintaining the amount and tection may be more suitable as genetic conservation areas the structure of genetic diversity. erefore, genetic reserves than some protected areas. More information is required to are selected and managed for genetic conservation purposes, ascertain which currently protected areas may also serve as typically chosen to refl ect the range and spatial structure of genetic conservation areas. More detailed information on genetic diversity within a species (and thus, reserves are cho- each of the Monterey pine populations follows. sen to be representative of areas that are genetically diff eren- tiated). e reserves are suffi ciently large to harbor eff ective Año Nuevo populations of a size that would not encourage inbreeding. Approximately ha have some kind of protected sta- tus. Using a total pine forest area of ha, this translates Status of in situ reservesreserves to three percent. In addition, a large, privately owned ranch Current Monterey pine protected areas have not been select- in the area—the Swanton Pacifi c Ranch—was donated to ed with genetic values in mind, and thus do not necessarily California Polytechnic State University in to be man- contain representative genetic variation, represent suffi cient aged for educational purposes. A mixture of agricultural habitat size or eff ective population size, or refl ect condi- and forested areas, much of the forest is dominated by tions that allow ongoing regeneration and adaptation. us, coast redwoods and Douglas-fi r. ere is also a signifi cant current protected areas are not necessarily in situ genetic component of Monterey pine, but separating this from the reserves, but some may off er the potential for including ge- redwood and Douglas-fi r forest type is subjective. ere are netic values in their management. perhaps ha that contain some natural Monterey pine for- e protected areas described in this section are those ar- est (W.R. Mark, pers. comm.). Because harvesting is includ- eas that have some offi cial status—conferred by law, agency ed in the management practices, and educational value is a objectives, or management policy of the landholder—that primary determinant in property management, this property restricts direct impacts on the Monterey pine forests, such has not been included within the protected area calculation as removal of trees for any other but conservation-related for the Año Nuevo population. Nevertheless, it is owned purposes. However, restrictions on the type of land use do and managed by a public institution and may have some not in themselves necessarily confer protection of genetic in- conservation value using diff erent criteria. 30 Most of the Monterey pine forest here is privately Cambria owned. ere has been some planting of nonnative trees in Until recently, only approximately ha within this this population. e Big Creek Lumber Company and oth- Monterey pine population had some kind of protected sta- ers have planted some trees in this area for forestry purpos- tus. At time of publication of this report, approximately es—some with local origins, but others from seedlings or ha ( or less of the total forest area, depending on which clones from New Zealand or other nonnative sources (L estimate for total forest area is used) have some form of pro- ). Approximately ha of Monterey pine forest are pro- tection. Purchases, acquisitions, and conservation easements tected within Año Nuevo State Reserve and Park, along the of forest by landtrusts, environmental organizations, the coast. e pine trees here, often with a prostrate phenotype, University of California, and others during – in- have been particularly aff ected by pitch canker and mortality creased the amount of protected area dramatically. Recently, is high (B.D. West-Bourke, pers. comm.). In the only other e Nature Conservancy purchased a conservation ease- publicly owned Monterey pine forest here—approximately ment on a -ha parcel, formerly known as the ‘CT Ranch’ ha within the Big Basin Redwoods State Park—Monterey and more recently referred to as the Cambria Coast Ranch. pines grow together with knobcone pine along ridgetops Of this area, approximately ha are Monterey pine forest towards the eastern (inland) extent of Monterey pine’s natu- (K.W. Smith, pers. comm.). Another area, with approxi- ral range. Natural interspecifi c hybrids(P. attenuata × P. ra- mately ha of pines and known as the ‘East-West Ranch’, diata), and advanced generations of these hybrids, have been was purchased as a park. e University of California’s observed in and close to this same area (B.D. West-Bourke, Natural Reserve System has signed a memorandum of un- pers. comm.; G and C ). derstanding (MOU) with the private owner of a pine forest property (approximately ha of which perhaps 1⁄3 is pine Monterey forest) to manage the property as a reserve. e property is According to a comprehensive review of this popula- known as the Kenneth S. Norris Rancho Marino Reserve tion conducted in (J & S A, I. (D.C. Canestro, pers. comm.). Greenspace— e Cambria ), approximately of the current Monterey pine Land Trust recently purchased an additional ha of pine for- area had some kind of protected status. e protected area est (R.H. Hawley, pers. comm.). then consisted of approximately properties, collectively e Rancho Marino Reserve, privately owned, will be amounting to about ha, and existed as undeveloped pine managed as a University of California reserve during the forest in parks, open spaces, and scenic easements (J & agreement period—until April . After this period, the S A, I. ). e purchase in of a reserve status is uncertain (D.C. Canestro, pers. comm.). previously privately owned ranch (the ‘Palo Corona Ranch’), Exact pine forest coverage is somewhat uncertain, but esti- by the Big Sur Land Trust and e Nature Conservancy, mated at ha. e pine forest canopy is fairly open and no added approximately ha of Monterey pine forest to the recent fi res (since early- to mid-s) have been recorded total protected area (L.W. Overtree, pers. comm.). ere- (M.R. Stromberg, pers. comm.). fore, this new area brings the portion of forest with protect- Prior to these recent acquisitions and agreements, the ed status to approximately for the Monterey popu- only pine forest area in the Cambria population over ha lation. Ownership of the protected areas is diverse: state, in size that had some protection was at the San Simeon State county, and city governments; land trusts; and foundations. Park with ownership and management by the California Management regimes and usage patterns are equally diverse. Department of Parks and Recreation. e park encompasses Most properties are essentially noncontiguous and many are ha of which approximately ha are Monterey pine for- surrounded by urban areas. None have been selected for, or est. Two notable pine forest types occur here, diff erentiated managed as, genetic reserves. Again, protected status is not by aspect, elevation, soil type, moisture regime, tree age and synonymous with natural or undisturbed condition. Many density, and co-dominant and understory vegetative spe- of the protected areas have been previously harvested, af- cies. Los Osos loam soils are found along the hilltop ridge, fected by pitch canker, planted with nonlocal Monterey while San Simeon sandy loam is located along the north-fac- pine, invaded by exotic invasive species, or aff ected by other ing slope. e elevation of the Monterey pine forest within management activities. the park ranges from to m. Fewer than California One assessment uses a combination of vegetation type, live oak are scattered within the Monterey pines along the soil development, and climate to suggest a stratifi cation ridge top, while no oaks or other tree species are found with system for selecting ecological reserve types for Monterey the Monterey pines on the north-facing slope. Sycamore pine in the Monterey area (J & S A, (Plantanus racemosa), alder (AlnusAlnus rubrarubra), black cottonwood I. ). Of the categories developed using this system (Populus trichocarpa), and willows (Salix spp.) are found in (including an ‘unknown’ category for unclassifi ed Monterey the riparian channel just below the pine forest. e shrub pine forests), it was determined that only three categories and herb layers are dominated by toyon (Heteromeles ar- (prequaternary shale, prequaternary granitic, and other butifolia), canyon gooseberry (Ribes menziesii), poison oak types) had suffi cient reserves. Whether this classifi cation (Toxicodendron diversilobum), and California blackberry system is an adequate proxy for within-population genetic (Rubus ursinus) (R.M. Orr,Orr, pers. comm.). Management poli- structure has yet to be tested. cies include fi re suppression and the most recent known fi re
31 in this park was approximately years ago (D.S. Hillyard, Genetic research on a portion of the seed collected in pers. comm.). ere is no evidence of logging within this is planned. is research will provide information on Monterey pine stand. Absence of logging history is con- the remaining amount of genetic diversity and the level of fi rmed by the Whitaker family—descendents of the Wash- inbreeding—information critical to appropriate conserva- burn family who owned this area prior to its conversion to tion or restoration decisions for the pines. An additional state park status (S.A. Hamill, pers. comm.). Some planting question is whether or not microenvironmental conditions of Monterey pine has occurred in nearby campground areas, remain that would support natural regeneration in the pines. including the Washburn (Upper) Campground and the San Given that small seedlings were seen in May in the im- Simeon Creek Campground. Seedlings planted in the late mediate vicinity of mature trees, at least germination and s were grown from seed collected in Cambria. A few initial growth is still possible. Fog condensation on pines Monterey pines that were planted earlier at the Washburn produces a considerable amount of moisture, so natural Campground were grown from local seed collections (H.W. regeneration may still be possible within the drip zone of Elliott, pers. comm.). Hence, there is no evidence that any existing trees as long as the goats are removed or controlled planting of trees from outside of the Cambria population before the remaining trees die. has occurred within or nearby this park. Some trees within this area are known overwintering sites for migrating Mon- Cedros Island arch butterfl ies. e island, under the control of the Ministry of the Inte- Some smaller pine properties are owned and managed rior, Mexico, has no offi cial overall protection or specifi c ge- for conservation purposes by Greenspace— e Cambria netic reserves for Monterey pine. Two fi res have occurred on Land Trust and the Land Conservancy of San Luis Obispo Cedros Island between and . According to a County. Collectively, these properties amount to approxi- visit to the island, reproduction of Monterey pine following mately to ha (R.H. Hawley, pers. comm.). the fi res was abundant, leaving a scientist to conclude that “Cedros Island remains the least endangered of the fi ve na- Guadalupe Island tive radiata populations.” (L ). DuringDuring the ex- Although the island is offi cially under the control of pedition (Box ), recent regeneration was noted in much of the Ministry of the Interior, Mexico and is a protected area the pine-covered area, suggesting another fi re within the last under SEMARNAT, Monterey pine has no specifi c protec- decade. Although the pines are largely restricted to ridge-top tion here. Furthermore, there are no specifi c genetic reserves areas, natural regeneration seems abundant. Genetic stud- for Monterey pine. e number of mature trees has dropped ies that are planned for some of the seeds collected in May dramatically since the informed estimate of (±) in may provide information on diff erences between the (B b). FewFew seedlings wwereere noted in the extremes in the pine range and levels of inbreeding within seed collection expedition and predation by goats intro- stands. ere could be some infl uences on the genetic diver- duced in the th century was continuing. e expedition in sity and integrity of the Monterey pines on Cedros Island— found approximately (±) trees (R et al. ), all of them large and presumably very old. A few Box . Removal and control of goats on Guadalupe Island. seedlings were seen, but are expected M B C- pine seedlings but none were planted to be eaten by goats in the near future. fornia have experienced negative eff ects in the natural stands because of lack of In situ conservation is challenging from introduced mammals (O funding. By , only six young trees sur- because of the stressful environmental ; MC and T ). vived in the nursery (L et al. ). conditions, continued heavy preda- Guadalupe Island is particularly impact- Two ranchers from Sonora, Mexico tion pressure from feral goats, and the ed. It has been recommended at various recently obtained permits from SEMAR- small number of seed trees (L times that the harmful introduced fauna NAT to remove goats from the island. As et al. ). Key to the maintenance on Guadalupe Island be removed (e.g., of October, , several thousand have of remaining genetic diversity of the M ; R C. b). Since been removed (J.A. Sanchez Pacheco, pines and the success of any natural their introduction, the goat population pers. comm.). e Island Conservation has fl uctuated dramatically, both from and Ecology Group (ICEG)—a bina- regeneration or restoration eff orts is climatic and associated vegetation cycles, tional nonprofi t organization dedicated the eff ective control or removal of the and from their slaughter. ere are re- to preventing extinctions and protect- introduced goats. is proposal has ports of over goats being removed ing natural processes on the more than been made at various times by diff er- in alone—over of those islands in northwest Mexico—has ent parties and may fi nally be mak- slaughtered and the rest removed live long-term plans for conservation on the ing progress (Box ). In the last two and taken to Ensenada, Mexico (M island. One of the fi rst steps they took, years, several thousand goats have been ). However, a goat-removal eff ort in , was the erection of fenced enclo- removed by Mexican ranchers and a must be large scale, comprehensive, well sures to keep goats out of the most sensi- binational not-for-profi t organization funded, and well coordinated if it is to be tive areas of the island until eradication eff ective in terms of island conservation. can be realized. (J.A. Sanchez Pacheco, has organized fence construction in In a small temporary nursery was pers. comm.). some critical areas, including three ex- fenced on the island to raise Monterey closures around some of the pines. 32 such as tree removal or browsing by introduced animals— in March . Seeds were distributed to Chile and South but these are not obvious or extreme, nor have they seriously Africa and most of this material has been outplanted into aff ected regeneration. the fi eld for the purpose of genetic testing and conservation banks. Several recent seed collections (–) have been made from the mainland populations specifi cally for use in Status of ex situ reservesreserves studies for resistance to pitch canker or for a source of possi- Ex situ collections may be held in a variety of states: planted bly resistant seedlings for mitigation plantings in residential collections, stored seeds, preserved tissues, and DNA and areas (R.H. Hawley, pers. comm.). DNA products. Seed collections are typically distinguished In general, Monterey pine seeds have good storage life from fi eld-based plantings, but both are dynamic states and under appropriate temperature and moisture conditions, experience selection pressures. e type of collection and its particularly as compared with many deciduous tree species. management or preservation conditions aff ect its utility in Seed can perhaps be stored for decades without signifi cant various conservation roles. loss of viability (L.A. Lippitt, pers. comm.). However, a seed As previously mentioned, an exhaustive review of all the collection event does not provide safe, perpetual protection ex situ reserves of Monterey pine, worldwide, is beyond the of genetic resources. “It is also risky to consider seed banks scope and not supportive to the objectives of this report. as ‘insurance’ against extinction in the wild. As with most First, such a review would be a massive undertaking in its insurance policies, you must continually pay the premiums own right: for example, a review of the genetic reserves of in order to be covered. We must avoid thinking that seed Monterey pine in Australia alone was an ambitious project banks are a one-time collecting eff ort ifex situ methods are (E a,b). Second, and more importantly, only a to be useful in preserving genetic variation.” (H fraction of the ex situ reserves worldwide would be relevant ). Germination tests done in on seeds collected to the goals of in situ conservation in the native populations. from the three mainland populations in and stored at However, it is important to describe the relevant portion CSIRO facilities (Australia) show a considerable reduction of those reserves—particularly those that could be used in in germination from () to (). ere is also restoration of native populations or those that predate some some suggestion of population variability in germination of the current infl uences on the native populations and thus rate (or storability), with the Cambria population showing could be useful for comparison purposes (e.g., collections lower percentage germination in () than either the that predate pitch canker infestations or collections from Monterey () or Año Nuevo () populations (E- trees on Guadalupe that are now dead). Finally, some of a). Because of notable diff erences in mean seed the domestic reserves are described in some detail to make weight among the fi ve populations, it is important to recog- a more public and permanent record of their location and nize these diff erences when estimating the number of seeds composition. Ex situ reserves of Monterey pine are selective- in any particular collection (Box ). ly reviewed here. Table . Major sampling events of Monterey pine populations since (adapted from B and E )†. Seed collections e fi rst European record of a specimen of Population Monterey pine collected from mainland California —— (Number of trees sampled per year) —— dates back to the La Pérouse Expedition of the s Año Nuevo – – – – (L and M ). Collections continued, sporadically, of all populations in the s and early Monterey – – – – s (F b; E b). e col- Cambria – – – – lections recorded in this document are those that are Guadalupe Island – – relatively recent—so as to have still viable seed in Cedros Island – – – – storage or resulting trees in cultivation—and with fairly large samples (Table ). Most of the seed col- Reference‡ lections and other ex situ reserves of Monterey pine †In addition, there have been several expeditions by Mexicans to Guadalupe meeting those criteria originated from a seed col- Island and Cedros Island with the objective of collecting seeds for both po- lection trip in primarily fi nanced and orga- tential restoration of the natural populations and ex situ conservation. During nized by Australia’s Commonwealth Scientifi c and the period of –, at least four expeditions to Guadalupe and Cedros Industrial Research Organization (CSIRO) and trips Islands were made by faculty and students from the Universidad Autónoma Chapingo to collect seed from Monterey pine (R S ). How- organized and fi nanced by the Central America and ever, only a few seeds remain in storage (most probably with a very low ger- Mexico Coniferous Resources Cooperative (CAM- mination percentage) from those collections (J.J. Vargas H., pers. comm.). CORE) in and (with some fi nancial assis- ‡Key: Moran (B ); FordeForde (F ); Libby, Bannister, tance from CSIRO). and Linhart (L et al. ); EldridgeEldridge and others (E a,b; CAMCORE and Carl Jackovich (with assis- L ); CAMCORE (D ); CAMCORE (D ); tance from Laurie Lippitt) made a seed collection Rogers, Matheson, Vargas Hernández, and Guerra Santos (R et al. of the three mainland populations, thirty trees each, ) 33 Some seeds from the and seed collections re- restoration purposes. For example, the apparent nonexis- main in storage in various locations in California (Table ). tence of pitch canker disease on Guadalupe and Cedros Is- Late in , individuals involved in maintenance, conser- lands suggests caution in moving seeds stored in California vation, and research (e.g., USDA Forest Service, California to those islands for any restoration activities. Risks are too Department of Forestry and Fire Protection (CDF), and high, currently, to allow seeds from California to be trans- University of California) met to discuss appropriate care and ferred to Australia or New Zealand. use policy for these remaining genetic collections in Cali- CSIRO (Australia) has approximately kg of Mon- fornia. One outcome from this assembly was consolidation terey pine seed in storage, with an average germination of of some seed collections: the collection previously held at when last tested in . A detailed description of the the Pacifi c Southwest Research Station of the USDA Forest Monterey pine seed in storage in Australia (mainly from the Service (Albany, California) was transferred to the CDF seed seed collection event for the fi ve native populations) is storage facility at Davis, California. contained in a report (E a). is collection Existing collections from Cedros and Guadalupe Islands contains more than seedlots from the fi ve populations. are of particular interest because of the protected status of e report, commissioned by the CSIRO Australian Tree Guadalupe Island, the real or potential decline of the popu- Seed Centre, contains recommendations on the best conser- lations since previous collections, and the considerable ex- vation strategy for this seed resource. A major recommen- pense involved in making new collections in these remote dation is that the seed in storage be outplanted (with the locations. e existing seed collections from Guadalupe exception of some seed in special long-term storage at Black Island, in particular, are in part irreplaceable because of the Mountain, Canberra) within the next two to three years in serious decline in parent trees and apparent genetic erosion well-designed genetic conservation plantings. It is suggested since the collection. e fate of seeds from these islands that, based on previous germination tests, germination may that were taken to Australia and New Zealand is described be low for many of the seedlots within as little as ten years. in Box . e seed in storage is considered irreplaceable—with the Seed collections can play a supportive role, but do not in uncertainty of safe quarantine procedures for new seed col- themselves constitute a long-term genetic conservation strat- lections from the native populations and the uncertainty of egy. “For sustained genetic conservation through stored seed, the current and future integrity of the genetic diversity in old seed would have to be grown out in plantations before it the native populations. erefore, restoration of the current loses its viability (to prevent the seed store from becoming a pure seed supplies may only be possible through expensive seed morgue) and replaced with pure seed of equal genetic controlled pollinations of the outplanted seed reserves (E- variability without loss of rare genes.” (E b). a). A recent update of this report shows that Concern over introducing diseases either from or into seed germination percentage has declined dramatically— the native populations of Monterey pine puts another con- to about (average of California populations) in straint on the transfer of seed for ex situ conservation or (E ).
Box . Diff erences in mean seed weight among the fi ve Monterey pine populations.
D estimates are based on seeds taken di- consider how the estimates were derived were one of the fi rst diff erences noted rectly from the native populations, these and whether the population diff erences among Monterey pine populations in na- ranking diff erences refl ect diff erences in have been refl ected in these estimates. tive conditions. Later, controlled studies the composition of the confi rmed a genetic basis for such char- samples (e.g., number of acteristics as cone dimensions, number trees sampled per popula- of scales, and mean seed weight (e.g., tion and number of seeds Mean seed weight (mg) B and L ). However,However, the weighed per tree) and pos- per population relative (mean) seed weight among popu- sibly other factors such as B K.G. Eldridge lations will vary according to the protocol those described above. Population b† pers. comm.‡ for the sampling procedure (number of To convert ex situ seed trees sampled per population and num- collections from a weight Año Nuevo . ber of seeds weighed in total and per basis to numbers of seeds Monterey . tree), moisture content (and so, maturity per population (i.e., when Cambria . of the seed, fresh or stored, amount of numbers of seeds are time in storage, and storage conditions), large), these conversion Guadalupe Island . environmental conditions, and other fac- estimates may be useful. Cedros Island . tors. Two reports on mean seed weight However, in making such per population show almost a twofold conversions to number of †Based on weighing approximately seeds per popula- diff erence in mean seed weight between seed in storage, to inform tion, except for Cedros Island for which seeds were the lightest and heaviest seed weights, but conservation policies or weighed (R.D. Burdon, pers. comm.). diff er in the ranking of the (lower three) seed management deci- ‡Based on weighing one hundred seeds per tree for each of populations. Because both sets of weight sions, it is important to the trees collected from the source populations in .
34 Planted domestic reserves pollinations, and established seed and hedge orchards and other research and conservation plantings at several central Most of the genetic conservation plantings for Monterey and northern California sites. Some of these plantings have pine in California were planted on University of Califor- already been removed; many others are at risk for removal nia (UC) property as a result of the initiative of W.J. Libby. for other land uses. For example, two hedge orchards on During the s and s, Libby and colleagues made University of California property containing clones from collections from native populations, conducted controlled all fi ve native populations were removed in and
Table . Monterey pine seed in storage in California in .
L.A. Moran USDA Forest Service Reforestation Center USDA Forest Service Albany, CA† Davis, CA‡ Placerville, CA Seedlot§ Seedlot size Seedlot§ Seedlot size Seedlot§ Seedlot size (count) (seeds/seedlot) (count) (kg) (count) (seeds/seedlot) Año Nuevo (AN) – . IT – Monterey – . – . IT Cambria – . – . IT Guadelupe Island (GI) – Cedros Island (CI) – – Date of collection & ¶ Within-population crosses†† AN × AN – Monterey × Monterey – Cambria × Cambria – GI × GI – CI × CI – Among-population crosses‡‡ Assorted crosses – Unknown or mixed †Germination tests conducted in show germination for open-pollinated seedlots (i.e., seeds collected from native stands) of to and for control-pollinated seedlots of approximately (D.L. Delany, pers. comm.). In , these collections were moved from the facilities at USDA Forest Service, Albany, CA to the California Dept. of Forestry and Fire Protection’s L.A. Moran Reforestation Center, Davis, CA. ‡A unit of the California Dept. of Forestry and Fire Protection (CDF). § e term ‘seedlot’ as used here stands for ‘unit of stored seed’. How such units are defi ned, measured, stored, and inventoried var- ies with the institution. A seedlot could mean in one case a bulked collection of seed from many individual trees and in another case a collection of seed from individual trees, the seed from each tree packaged and kept separate from the others, but regarded alto- gether as one unit. e latter case, when known, is denoted by the letters IT (for individual tree) in the seedlot size fi eld. Seedlots are from the seed collection trips (D.R. Johnson, pers. comm.) by Eldridge and others (E a,b; L ). ¶Individual tree collections (IT) are from CAMCORE collections, while all others are from . ere are also small amounts of seed in cold storage at North Carolina State University from the CAMCORE collections. ere are also small quantities of seeds in storage from six individual trees at Año Nuevo, collected by Dave Adams (CDF). Four of the trees appeared resistant, at time of collection, to pitch canker; the other two appeared susceptible (L.A. Lippitt, pers. comm.). ††Within-population crosses were made in through by W.J. Libby. ‡‡No further information is available for this material. 35 Box . Fate of Australia and New Zealand collections from native Monterey pine populations from Guadalupe and Cedros Islands.
AUSTRALIA: “I -- -°C and Año Nuevo, very little Cambria, no “In addition, we have a small block of storage at CSIRO Plant Introduction Guadalupe, and a little of Cedros.” (K.G. pure but unpedigreed Guadalupe materi- Laboratory, Black Mountain, Canberra Eldridge, pers. comm.; more details in al, which produces a mix of purebred and there are about seeds of each of about E a) hybrid seed, the purebred component be- mainland families, Cedros, ing at least free of most of the inbreeding Guadalupe, and also of each of NEW ZEALAND: “We received Guada- of in situ seed. Guadalupe families from the col- lupe families (from the collection “Regarding the Cedros material from lection. We expect all this old seed will trip) which went out into a pedigreed the collection, of which Ken Eldridge germinate well, after stratifi cation, as it planting in Kaingaroa Forest. From a sent some to New Zealand, we have a tale was extracted under relatively benign combination of this planting, and earlier of total loss, in which the fi nal, decisive conditions and has not had the quaran- plantings (‘Genetic Survey’, i.e., prov- chapters stemmed indirectly from our in- tine treatments of sodium hypochlorite enance-progeny trial) from families stitutional changes. However, we do have dip and methyl bromide fumigation. collected by Reid Moran (in ) and some material, representing less than “In the cold room at CSIRO Forestry fi ve by Libby et al. (in ), about families, plus some unpedigreed trees, left and Forest Products Laboratory at Yar- good phenotypes have been selected and from the Libby et al. collection in early ralumla, Canberra there is more than are being intercrossed (in archives) to . Ten or so clones have been archived kg of the seed which probably maintain pure Guadalupe material. ere and are being used for some crossing. has low germination due to inappropri- is also controlled crossing being done to “No seeds from the trip remain: ate quarantine treatment in and produce F hybrids with our local, main- we have sown everything and planted imperfect storage since. Within this land origin, stock as a pilot commercial out what resulted.” (R.D. Burdon, pers. collection, there is plenty of Monterey operation. comm.).
(L ). InIn addition to prpressuresessures frfromom competing land years. e fi eld trials are expected to be continued for per- uses and uncertain funding provisions, the UC collections haps three more years. As the original hedge orchard from remain at risk from western gall rust, pitch canker, and, at which these cuttings were derived has been destroyed, the some locations, fi re. principal investigator for this experiment, Detlev R. Vogler, At the University of California’s Russell Reservation, plans to ‘reconstitute’ the hedges by taking cuttings from the near Berkeley, California, several Monterey pine plantings ramets in the fi eld. If successful, this source of germplasm are maintained. ree breeding orchards were established may be perpetuated (D.R. Vogler, pers. comm.). here in –. One orchard was planted in with At another UC property in Albany, California (Gill open-pollinated seedlings from trees on Cedros Island Tract), part of the mainland population breeding orchard (from a seed collection trip). Another was planted with was replicated. In , approximately clones were re- seedlings from trees sampled from Guadalupe Island. A moved to install a sewer line. A -clone hedge orchard third was planted with close to clones from trees in the was also established here that occupies approximately . ha. three mainland populations ( from each). ese trees orig- Neither planting is well maintained and the future of the inated from a collection of eight trees within ten select- material here is uncertain (M.A. Diegan, pers. comm.). ed stands of each of the three mainland populations. ese Ramets from half of the clones in the mainland pop- orchards are not suffi ciently distant from one another for ulation breeding orchard at the UC Russell Reservation were genetic isolation and controlled crosses would be required planted in northern California. e property, near Korbel, to be assured of pure-population progeny. A hedge orchard California, is owned by the Simpson Timber Company. was established here, originally with clones. It was re- propagated in , but an informal UC report says it International ex situ reservesreserves and was then dying of western gall rust. Various other plantings interest in the native populations occur at this site, including an exhibit with representatives For well over a century, there has been much inter- of all fi ve native populations plus some interpopulation hy- national interest in Monterey pine, particularly from the brids. A series of fi eld studies were installed here in the early southern hemisphere (Box ). Monterey pine is grown as s to determine family and population diff erences in re- a plantation species in Chile, New Zealand, Australia, and sistance to western gall rust (e.g., O et al. ). to a lesser extent in Argentina, South Africa, Spain, and Another set of fi eld trials at the Russell Reservation, several other countries. Combined, the countries that have planted in , contains material from all fi ve native popu- commercial plantations of Monterey pine have more than lations, mainland × island crosses, and selected families from million ha in production (Table ). is is over six times Australia and New Zealand. A total of clones are replicat- the plantation area recorded in the mid-s (S ). ed on four sites. e four fi eld trials, established with rooted Current trends suggest that the Pacifi c Rim countries are cuttings, were intended to test for diff erences in resistance to increasing their dominance in Monterey pine plantations western gall rust. e diff erence in response is dramatic after (L and M ). 36 More detail on the history and nature of Monterey pine would disappear in the next – years unless determined plantations worldwide is available elsewhere (e.g., L action is taken now to recognize its value, preserve the best and M ). e focus here is on providing a brief de- of the present plantings beyond the normal rotation age, scription of the commercial context of Monterey pine, to and plan for their replacement.” (E b). the extent that there are genetic resources internationally Argentina. e area of Monterey pine plantations is ap- that could be considered ex situ reserves with relevance to proximately ha and has not changed signifi cantly in genetic conservation of the native populations. Summaries the last decade or so. One of the main limitations is fi nding and comparisons among countries are complicated because appropriate sites with suffi cient moisture, especially during breeding and conservation programs in these countries diff er the summer months. Some plantations, established to considerably in the extent of documentation of the original years ago in areas with annual precipitation of over collections that form the basis of their programs, the degree mm, now lie within the boundaries of national parks. ese of recording the breeding histories of existing material, and plantations show very good growth. e other plantations in the units and variables by which the plantings are described. Argentina are mainly in Cordoba province and along some Much of the information provided here is derived from Altantic coastal areas in Buenos Aires province (L.A. Gallo, responses to a 1998 questionnaire (a list of respondents is pers. comm.). provided in Appendix B), supplemented by several specifi c reports on the Australian and New Zealand reserves and in- Australia. Sources of information on the Australian breed- formation off ered through recent personal communications. ing program for Monterey pine include M and Genetically pure reserves—having not been shaped by B (), C (), E (), B- artifi cial or natural selection in the host (nonnative) coun- (), M et al. (), and many others. e try—are not only in the minority among germplasm re- description here will focus on the genetically pure ex situ serves in these countries, but are the most valuable towards reserves. e major organization with research and conser- conservation or restoration of native forests. ere is an im- vation interests and historically and currently making large portant distinction here between germplasm that can serve investments in these activities is the Division of Forestry and as an ex situ genetic reserve for the native populations versus Forest Products, CSIRO. that for plantation purposes. Substantial genetic reserves for An excellent summary of much of the outplanted Aus- Monterey pine exist internationally, but pure-population tralian germplasm is provided in an annotated catalogue of reserves are a small proportion (i.e., perhaps a few hundred Australian provenance trials and genetic conservation plant- ha of provenance trials and stored seeds) and are at risk from ings (E b). ere are such trials in Australia, a variety of threats. At some point, the stored seeds must be the earliest planted in . Of these, no longer exist (i.e., grown out and, in so doing, are subject to selection pressures harvested, burned, abandoned, or lost). e total area of the diff erent from those in the native populations and, in some remaining plantings, as of , is approximately ha. cases, genetic contamination. “ e option of maintaining ere is good representation, among the remaining trials, of pure native-population stocks as gene resources in New Zea- all fi ve native populations. land is threatened by ubiquitous pollen contamination from Forty-fi ve of the remaining trials contain trees derived plantations, unless massive controlled-crossing operations from the seed collection eff ort organized by CSIRO, are practiced.” (B et al. b). Planted reserves are most having been planted between and . A recent vulnerable to a variety of risks and are diffi cult and expensive fi eld inspection of six of these plantings revealed both con- to maintain in the long term. “[In Australia] it is clear that, servation opportunities and problems (two in Gippsland, in a time scale of several rotations, the present ex situ radiata Victoria on Australian Paper Plantations land and four near pine genetic conservation plantings must be regarded as Tumut on State Forests New South Wales (NSW) land) EPHEMERAL [sic]. ereere will be a considerable challenge (K.G. Eldridge, pers. comm.). Because these fi eld plantings to continue to have such uncontaminated ‘wild’ material are now approximately years old, and were planted at a still available in years, and it seems likely that most of it spacing that required some selective thinning, they are not well designed for long-term growth comparisons. e tests were planned Box . Early observations on the commercial signifi cance of not only for genetic conservation but Monterey pine. also for shorter-term genetic testing. us, some trees have been, or will be “T - invested in these operations. Quite insig- soon, removed. Natural mortality is tant conifer from the view point of nifi cant in its native habitat, on the coast not random within the plantings. For commercial aff orestation that has been of California, its rapidity of growth and example, the Cedros and Guadalupe introduced to countries of the southern adaptability to a wide range of condi- Island trees, at two of the NSW areas, hemisphere, Australia, New Zealand tions in many countries of the southern have suff ered heavy mortality and thus and South Africa. Planting of the spe- hemisphere, render it an invaluable spe- cies has now been going on for to cies in providing softwood supplies to some plantings do not have the same years and a very considerable amount of meet the shortage in that region.” (L- conservation value as they did when capital, both State and private, has been ). planted for all fi ve populations. Active management and thoughtful consid- 37 eration of these plantings will be required to main- Table 11. Estimate of plantation area of Monterey pine internationally. tain some of their genetic conservation potential in Area in the long term. Most of the plantings from the Country plantations Reference seed collection—in both Australia and New Zea- land—are due for clear-cutting within the next (ha) years (K.G. Eldridge, pers. comm.). A report that Argentina R and L provides an update of the status of both CSIRO Australia From survey (unpublished data) fi eld plantings and seed reserves of Monterey pine Chile R and L and recommendations for their management has Great Britain C.J.A. Samuel, pers. comm. been recently published (E 2002). Ireland D.G. ompson, pers. comm. ere is continued strong interest in the con- servation of the native gene pools in situ. Because New Zealand From survey (unpublished data) of the many problems associated with ex situ con- South Africa DWAF servation of pure-population genetic resources, Spain From survey (unpublished data) Australian plantation managers and owners value Turkey B.N. Cengel, pers. comm. the native populations as a source of new genes. It is acknowledged that technologies and biosafety pro- Total tocols would be required to prevent introduction of disease (such as pitch canker) into Australia if new collections Island, suggested to researchers that it may be desirable to were made. Also, there is concern about genetic contamina- incorporate material from the natural populations directly tion of the Monterey and Cambria stands due to the planting (rather than just continuing with domesticated material) of trees raised from New Zealand seed (thought to be largely into Chilean tree improvement programs (J of Año Nuevo origin), the uncertainty of property owners al- and B ). lowing future seed collections, and the serious decline of the Breeding and selection has contributed to shaping a Guadalupe Island population (E ). genetic resource that is more appropriate for the plantation Australia’s interest in and commitment to the conserva- conditions and market needs in Chile. ese localized genet- tion of the native gene pools in Monterey pine has been ex- ic resources are important for commercial conservation pur- pressed for decades in such activities as sponsoring expensive poses, but less valuable in relation to conservation of the na- seed collection expeditions (e.g., ), provision of funds to tive Monterey pine forests. A breeding program that began the University of California for genetic conservation (e.g., in has resulted in more than ha of seed orchards, L ), establishing numerousnumerous prprovenanceovenance trials, con- more than full-sib families in progeny trials, as well ducting considerable genetic research, and organizing work- as clone banks and hedge orchards. e response to a shops and meetings to discuss the importance of genetic survey suggested that the genetic reserves were considered conservation and appropriate policies and procedures for ex adequate for the future of the breeding program in Chile. situ genetic conservation collections. However, long-term genetic conservation is not institution- alized here because the plantation property and reserves are Chile. Monterey pine was introduced to Chile in the late all privately owned: forest industries own approximately s. Later, there was interest in using this species to help of the Monterey pine plantation area and smaller pri- stop erosion problems that threatened the Coastal Range. vate landowners the rest (R and L ). e fi rst commercial plantations were planted in the early s and today Monterey pine constitutes the basis of the Great Britain. ere are currently almost ha of Mon- Chilean forest economy. Exports from these plantations terey pine plantations in Great Britain, approximately contributed over . billion USD in to the national evenly divided between public (Forest Enterprise) and pri- economy (T and G ). Little is known about vate ownership. Most of the publicly owned Monterey pine the source of the seed used for early plantations (J- plantations are located in Wales or the southwest England and B ). Because the cone sizes and seed peninsula. Monterey pine is also used as an ornamental tree, weight from the plantations are similar to those found in particularly common along the south coast of England. New Zealand landraces, it has been suggested that the seed Species and provenance trials of Monterey pine have source of the Chilean Monterey pine is the same as that for been planted, particularly in the Bournemouth area. One of New Zealand, namely the Año Nuevo and Monterey popu- these fi eld trials, planted in , contains trees from seeds lations (R.D. Burdon, pers. comm.). collected from planted Monterey pines in southern England Several provenance trials, comparing the growth of as well as samples from the three California native popula- Monterey pines from the fi ve natural populations and tions and some Australian-source material from Guadalupe several foreign and domestic seed orchards, may be con- Island (i.e., Guadalupe ex Canberra). e California main- sidered ex situ reserves. Measurements show diff erences in land and Guadalupe material was obtained from CSIRO. volume among the various source populations. e good irteen-year results show that the best height growth and growth rates of some of the subpopulations, and the desir- survival are found among the home-collected seed sources, able straight stems shown by the material from Guadalupe showing that a single generation within Britain can have a
38 benefi cial eff ect. is observation has also been made for (relative to other populations) severity of symptoms from other exotic conifers in which a comparison is possible be- Cyclaneusma disease (D.G. ompson, pers. comm.). Plan-Plan- tween directly imported germplasm and fi rst-generation tation area of Monterey pine—Guadalupe source in particu- domestic seed collections (C.J.A. Samuel, pers. comm.). e lar—may increase, particularly in the south near Cork, as Guadalupe material also showed good survival and growth. some of the practical and technical limitations are overcome Among the three mainland populations, the Año Nuevo (Box ). material generally had the best survival. (C.J.A. Samuel and R.L. Jinks, pers. comm.) New Zealand. Although records have not been exhaustively searched, it appears that Monterey pine—as germplasm Greece. e fi rst recorded introduction of Monterey pine to rather than a wood product—was introduced in the late Greece was in as a addition to the Arboretum of Vytina. s (R.D. Burdon, pers. comm.). As with Australia, Monterey pine is currently a minor plantation species here there is a sophisticated and long-established breeding, and is limited to particular sites that have suffi cient moisture genetic research, and germplasm conservation program and microclimate (V ). here for Monterey pine, much of it provided by the New Ireland. Monterey pine is a minor but important plantation Zealand Forest Research Institute, based in Rotorua, New species in Ireland, currently growing in plantations of total Zealand. Some sources of information on the breeding area of approximately ha. It adds to species diversity, has programs include S (), S et al. among the highest wood production rates of forest planta- (), J et al. (), S (), tion species there, and grows on less fertile sites than Sitka S et al. (), S et al. (), and spruce (Picea sitchensis)—another favoredfavored plantation species many others. As with Australia, the description of genetic with similar yields. Guadalupe Island is the seed source of reserves will focus on those that are the most genetically most interest for the plantations, primarily due to its lower pure derivatives from the native populations.
Box . Commercial signifi cance of Monterey pine in Ireland.
“F I - problems with Monterey pine in Ireland priate sites, and assuming that we can de- tween Coillte Teoranta—the Irish For- have been: ) determining the site re- velop a reliable source of Guadalupe seed, estry Board (i.e., forests established under quirements; ) determining the right seed the question of producing high-quality state forestry –)—and privately origin; and ) development of quality planting stock is the remaining limiting planted, owned, and managed forests. nursery stock. factor. Instability or ‘toppling’ of young, For Coillte, we have ha of Monterey “We now know on what sites it per- container-grown plants is the major prob- pine in our inventory out of a total of forms well and they are typically nutri- lem at present. It appears that there is an ha or about . of our forests. No ent-poor soils where sitka spruce requires inappropriate allocation of photosynthate current details of Monterey pine in the large amounts of repeated fertilization. It to shoot growth relative to root growth. private sector exist, but a survey done in also provides variety to forest plantations, Monterey pine has the reputation of found only ha. both visually and perhaps ecologically, being diffi cult to transplant so container- “ e genetic base is rather unclear providing unique habitats for diff erent ized planting stock seems to make sense. because although there is a register of all plants and animals. Provenance trials Cultural practices such as sowing date, seed imports for the period to , established in the early s identifi ed fertilizer rates, and other nursery practices there was little attention paid to the exact Guadalupe Island as the most produc- are probably critical in the production origin of imported seed until perhaps the tive seed source, mainly because we have of high-quality planting stock. I do not s or s. erefore, the seed source found much lower levels of Cyclaneusma think that the production of bare-root is generally recorded as ‘western North disease in this seed source. e Cycla- plants will overcome these problems. America’ or ‘California’. neusma infection greatly reduces needle “We plan to increase planting of Mon- “ e average yield class (i.e., volume of area which results in greatly reduced terey pine in the southern part of the wood produced per ha per year) of Mon- wood production. We have tested some country around the Cork area because of terey pine in Ireland is . cubic meters of the ‘Guadalupe ex Canberra’Canberra’ material the warmer temperatures and the avail- which is among the highest species pro- from Australia and unfortunately fi nd ability of sites where Monterey pine does duction rates recorded here. Nevertheless, that it has considerable yellowing due to well with only modest fertilization (i.e., Sitka spruce (Picea sitchensis)—which has hybridization with local Monterey pine. nutrient-poor, old, red, sandstone-derived about the same yield class—grows on a is is the reason why we are interested soils). If we can overcome the toppling much wider range of sites than Monterey in obtaining a source of pure Guadalupe problem and have a verifi ed seed source, pine and therefore is the major commer- island material. We also had a programme I expect that planting of Monterey pine cial species. of collecting seed and scions from local will increase. It will never become our “ ere has always been an interest in individuals of unknown origin that did major commercial species, but in light of Monterey pine in Ireland because of its not exhibit the yellowing problems, but the current emphasis on biodiversity, it productive potential. One of my col- they also are not as productive as the pure could play an important role in certain leagues says: ‘Every generation of forest- Guadalupe Island material. parts of the country.” (D.G. ompson, ers rediscovers Monterey pine’. e main “Given that we have identifi ed appro- pers. comm.).
39 Seed collections from , , and (Table ) are they are underrepresented in landrace stocks in New Zea- represented in breeding-population parents from fi eld plant- land (as compared with Año Nuevo) and because of the gen- ings for Año Nuevo, Cambria, Monterey, and Guadalupe eral adaptedness of trees from this population, particularly populations. However, there are now some dramatic diff er- in the north of the country. Año Nuevo is well represented ences between the original collections and the remaining in the landrace stocks, tending to reduce interest in the na- trees. Some fi eld plantings have been felled or thinned. Also, tive population. However, its general adaptedness to New natural selection for New Zealand conditions (disease and Zealand conditions, particularly in the south, could refocus general local adaptation) has removed some of the trees, and interest on the native germplasm if landrace stocks and the thus, truncated genetic diversity. Approximately to breeding population could not meet some need that arose. of these original collections of the three mainland popula- ese native genetic resources are diffi cult to maintain ex tions have been lost in the fi eld from a combination of thin- situ. Perhaps the greatest concern is that the native popula- ning and natural selection. Representatives from up to tions remain in a condition that enables them to continue to parent trees from Guadalupe Island have been installed in regenerate, maintain diversity, and give rise to trees that are fi eld plantings. One-third to one-half of these trees has been resistant to pitch canker or any other pest that might reach lost either from planned harvesting or disease or other natu- California before eventually reaching New Zealand (R.D. ral selection. Approximately one hundred parent trees from Burdon, pers. comm.). Cedros Island were represented, via seeds collected, in fi eld plantings. Probably the majority of these have been lost. In South Africa. Monterey pine is very important for the Cape general, material collected from the seed collection trip region, particularly the Monterey population. Provenance (from mainland populations) has been partially harvested trials, containing material from the three mainland popu- and the remainder will be removed in the foreseeable future. lations and some Canberra-collected seed of Guadalupe Plantings from the Cedros Island population, in particular, origin, have been replicated on six sites. Assessments have have largely vanished owing to a combination of suppres- shown that there are not signifi cant diff erences among prov- sion by trees of faster-growing material and low interest in enances within populations (of the traits assessed), but the the genetic resources from this source for the breeding pro- superior population varies by trait and by trial site (F- gram (R.D. Burdon, pers. comm.). In addition to these pure ). population collections, some breeding-population selections Aside from the provenance trials, much of the germ- have been made from these collections and planted in new plasm has been shaped in some way towards local condi- fi eld sites. tions, and is less valuable as an ex situ genetic reserve rela- Risks of low to moderate levels include fi re, climate tive to the native populations. A Monterey pine breeding change, and ash eruptions from active volcanoes. Pollen con- program initiated in by the South Africa Department tamination is potentially a major (if poorly quantifi ed) risk of Forestry has been taken over by the South African For- in connection with any attempt to maintain reasonably large estry Company Ltd. (SAFCOL). e basis for this program native-population entities in New Zealand without con- was a selection of superior trees from close to trolled pollination. New diseases or pests, whose behavior in ha of Monterey pine plantations in the Cape Province. New Zealand conditions is unpredictable, present additional ese plantations contained a mixture of trees from some risks. Perhaps the most pressing and most certain risk comes of the native populations. Of these, were approved for from institutional and political conditions: despite policy use in the breeding program, and were supplemented with protection for these reserves, institutional upheavals may some trees from Australia and New Zealand. Open-polli- generate both human error and a lack of funding which un- nated seed orchards were established with the best of these dermines eff ective, long-term conservation strategies (R.D. selections. Seventeen progeny trials were established with Burdon, pers. comm.). representation as follows: selections from open-polli- Although there is a sophisticated tree improvement pro- nated progeny from the seed orchards, open-pollinated gram here with advanced domesticated generations and lo- and full-sib families from Australia, open-pollinated cal landraces, native gene pools are still considered valuable. families from New Zealand, and full-sib families from For example, Monterey germplasm may improve edaphic local breeding eff orts. Selections were then made from these tolerances and Guadalupe germplasm may be useful in im- progeny trials to form the basis of a breeding population. proving stem form and wood quality and possibly snow Two second-generation progeny trials ( selections) and a resistance (B et al. b). Currently, there is strong second-generation seed orchard ( selections) were estab- commitment to maintaining the New Zealand plantings of lished (D.J. Steyn and H. Rossouw, pers. comm.). ere is Guadalupe as a pure population that can be used to produce a high degree of risk to germplasm from fi re and a moderate F crosses with local, improved stock for commercial plant- risk from disease (C. Bester, pers. comm.). ings (R.D. Burdon, pers. comm.). Conservation and intro- gressive use of the Cedros Island and Cambria populations Spain. ere are three seed orchards established with materi- may also be of real value because of unpredictable benefi ts al from the Año Nuevo population, each with approximately of completely new gene combinations and to help meet un- trees. ere are also three progeny tests with seedlings foreseen selection criteria that might emerge in the future from the plus trees (i.e., trees selected, based on phenotype, (B ). Monterey gene pools are also of interest as for desirable traits) from these seed orchards. For each of 40 the Cambria and Monterey populations there is one seed Turkey. e Monterey pine plantation area is approximately orchard, each with approximately trees. ere is also one ha. e genetic source for these plantations is known small seed orchard with trees of unknown origin. in some, but not most, situations. e only genetic reserve is Monterey pine is a very important species in the north a plantation in northwestern Turkey, near Adapazari, that is of Spain. It grows in over ha in the Basque country growing well and protected as a seed production area. Inter- (E et al. ). e Monterey population, in particu- est in Monterey pine as an exotic plantation species is not lar, is of great importance in the Basque country because this increasing. In , many plantations suff ered damage from population shows growth performance superior to the other Evetria buoliana and interestinterest was lost in MMontereyonterey pine as three mainland populations in fi eld tests here. a result. However, some trees have almost totally recovered (B.N. Cengel and Z. Kaya, pers. comm.).
41 42
Models of genetic conservation plans
he United States does not have a com- and scientifi cally sound conservation strategies. prehensive strategy for conserving forest Some European countries have overall plans for their genetic resources or a national program forest tree species or plans for some species of particular eco- for long-termT ex situ conservation of forest genetic resources nomic importance. A strategy for the conservation of the ge- (R ; L et al. ). Some European countries netic resources of tree and shrub species in Denmark was are more proactive and have some level of national planning prepared in the early s (G et al. ). is strat- for forest genetic conservation. Many European countries egy was based on the recognition of the historical and con- are members of a coordinated eff ort to ensure the eff ec- tinuing infl uences on genetic diversity in these species, and tive conservation and the sustainable use of forest genetic the need to make a focused and systematic eff ort to conserve resources in Europe. is organization—the European For- the adaptability and utility of these species in the long term. est Genetic Resources Programme (EUFORGEN)—was A guide for planning national programs for conservation of established in as an eff ective means of promotion and forest genetic resources has been developed by geneticists in coordination of in situ and ex situ conservation of genetic di- Denmark (G et al. ). is is an excellent guide, versity, exchange of reproductive materials, and monitoring particularly for situations when there are numerous species progress in these areas (T et al. ). e organization that are widespread in their natural ranges, thus requiring is coordinated by the International Plant Genetic Resources the setting of priorities and the selection of conservation op- Institute (IPGRI), in collaboration with the Department portunities such as determination of genecological zones, of Forestry of the FAO. Much of the work is conducted socioeconomic values, and conservation methods. Another through smaller groups—known as networks—that focus on example is the Finnish network of in situ gene reserve forests genetic conservation issues for a particular species (e.g., Pi- for their major commercial forest tree species (K ). cea abies, Quercus suber, Populus nigra) or groups of species. In general, though, there are few comprehensive networks rough this coordination, complementary conservation of reserves dedicated to in situ genetic conservation of forest activities can be undertaken and much or all of the natural tree species, although there are many examples, worldwide, range of a particular species can be considered. of reserves to conserve the genetic resources of a particular A similar type of cooperative—the South Pacifi c Region- population of a taxon (K and B ). al Initiative on Forest Genetic Resources (SPRIG)—aims Few cases exist that can serve as a direct and complete to provide coordination and support for planning genetic model for a genetic conservation plan for Monterey pine— conservation and management of forest tree species in this concerning a single forest tree species, covering the entire region. For example, general strategies for the conservation, natural range of the species, containing both ex situ and in management, and utilitization of Highlands Yuka (Dac- situ elements, and focusing on the genetic structure, under- rydium nausoriense) in FijiFiji and SSantoanto kauri (AgathisAgathis silbæ) lying principles, and opportunities for genetic conservation. and whitewood (Endospermum medullosum) in Vanuatu have Existing single-species conservation plans are more gener- recently been produced (T et al. ; C et al and often do not include a comprehensive description al. a; C et al. b; respectively). All three are of genetic variation or enunciate genetic principles. Many economically valuable species and more research has been plans are concerned with a threatened or endangered species recommended towards the development of comprehensive with little natural habitat and few opportunities for specifi c 43 genetic conservation (e.g., species recovery plans of the U.S. necessarily consider the institutional values and responsibili- Fish and Wildlife Service). Existing genetic conservation ties with which DNR is charged, which are broader than plans are often only concerned with ex situ resources (e.g., genetic concerns (J.D. DeBell, pers. comm.). S et al. ) or areare rrestrictedestricted bbyy jurisdiction (e.g., Internationally, there are examples of forest tree species state or agency) and thus do not consider the full natural that are of particular conservation concern and have atten- range of the species (e.g., W ). tion focused on the conservation of their genetic diversity. In North America, perhaps one of the highest-profi le A genetic conservation plan has been developed for Leucæna forest tree species with considerable attention provided to salvadorensis, a threatened tree species native to El Salvador, conservation of its genetic resources is Douglas-fi r. Like Honduras, and Nicaragua (H and H ). It Monterey pine, this is a commercially valuable species. But has a largely contiguous distribution in the seasonally dry, unlike Monterey pine, Douglas-fi r has a wide natural range deciduous tropical forest association on south-facing Pacifi c that extends from western Canada through many western slopes. Its genetic resources have been severely degraded states in the USA and into Mexico. Although there is no as a result of habitat loss to farming. In situ conservation rangewide overall genetic conservation plan for Douglas- methods are compromised because very little natural habitat fi r, particular reports and activities have been undertaken in remains. However, farmers have traditionally maintained specifi c regions. An assessment and conservation plan for the some trees of this species around houses and in fi elds and genetic resources of Douglas-fi r in California were prepared fencelines, meaning that the species has more presence than in the early s (C G R P would be indicated by the loss of forest cover. ere is, ). Another regionally focused eff ort is the establish- therefore, an opportunity here to encourage the interest and ment of gene pool reserves of Douglas-fi r in the state of traditional protection by farmers, involving them in seed Washington (W ). is in situ conservation plan collection, planting, and protection eff orts.L. salvadorensis is restricted to that part of the species’ range that occurs on can grow on shallow soils and under drought stress, produc- public (i.e., State of Washington Department of Natural Re- ing high-quality wood. Accordingly, its genetic resources are sources (DNR)) forests in Washington state and focuses on valued as a possible means of improving the widely cultivat- in situ reserves. ese reserves were established in recogni- ed congeneric species, L. leucocephala, as well as other spe- tion of concern over genetic contamination of natural popu- cies with domestication potential in their own right. lations of Douglas-fi r due to increasing areas planted with English yew (Taxus baccata) has a natural distribution genetically improved seeds that were derived from a fraction throughout most of Europe, yet remains as part of a natu- of the species’ natural genetic variation and concern for the ral plant community in only a few stands and is generally largely unknown eff ects from selection pressure due to for- considered to be a declining species. It is also cultivated for est management practices. Reserves (areas protected from ornamental purposes. One of the largest protected areas— harvesting) were established according to elevation and seed the Wierzchlas Reserve in Poland—has suff ered a major loss zones—the latter refl ecting genetic diff erentiation among in number of living yew trees in the last years. Genetic populations. As of over gene pool reserves had been analysis showed that this loss is not a direct result of low located and designated, amounting to ha or . of genetic diversity in this population (L et al. DNR forest land. Although selection criteria favored the ), as previously thought. In fact, there is apparently high designation of old-growth areas, this was not always possible genetic diversity within this species as compared with other due to historical harvesting practices. us, some gene pool conifers. e genetic study turned attention over the spe- reserves, particularly those in lower-elevation and higher-ac- cies’ decline towards environmental factors that limit natural cess forest areas, were second generation. However, records regeneration, such as soil pathogens. us, the value of the were checked to ensure that the regeneration in these areas Wierzchals Reserve as a gene pool reserve and the need for a was natural. ese reserves were designed and selected with longer-term genetic strategy, including ex situ conservation, the best available information. Ongoing concerns include have been recognized. genetic contamination from adjacent (and artifi cially regen- e conservation of wild relatives (usually congeneric erated) forests and loss of gene pools by natural disturbances species) of agricultural crop varieties has become a shared such as fi re. priority of agricultural geneticists and conservation biolo- e DNR gene pool reserves for Douglas-fi r also provide gists (F and S ). Because the domestic use experience on the challenges of maintaining an in situ genet- of improved germplasm far exceeds the census of the natural ic conservation program over time. Since implementation, populations, conservation of the native populations of Mon- approximately of the reserves have been administrative- terey pine could be considered in this light. From this per- ly lost—that is, traded or transferred to diff erent ownership. spective, the value of conserving the native gene pools is not Some of those reserves aff ected can still function as genetic only to protect the genetic source of derived families, but to reserves under the new ownership but the coordination and safeguard the opportunity to understand the web of ecologi- management necessary to achieve specifi c genetic outcomes cal relationships and coevolved species and thus to provide have been lost or lessened. e DNR maintains a strong unique (i.e., unavailable in ex situ repositories) opportunities commitment to their genetic conservation policy. However, to improve the breeding or management of domestic germ- over time, decisions about land transfers and management plasm (T et al. ).
44
Principles and recom- mendations for in situ genetic conservation of Monterey pine
his chapter contains a review of genetic earlier section and is not repeated in subsequent sections. principles that are most relevant to genetic Recommendations can be meaningless, or even coun- conservation of Monterey pine, a descrip- terproductive, if taken out of context. Considerable care tion of issuesT and infl uences (mostly anthropogenic) on na- has been taken in providing an appropriate context for the tive gene pools, and a set of recommendations for genetic recommendations provided here. e specifi c recommenda- conservation. e selection of principles and issues has been tions are off ered as one set of expressions of underlying prin- undertaken from an inclusive, species-level perspective, al- ciples of genetic conservation but are by no means exhaus- though some issues and recommendations are more (or ex- tive to all possible situations. Good guidance—perhaps even clusively) relevant to certain populations than to others, and more valuable than specifi c recommendations—can be de- this is noted where pertinent. rived from an understanding of the principles and rationale Issues and infl uences have been discussed within discrete used in developing recommendations. is understanding topics, but it should be kept in mind that they are interac- will allow readers to better translate the information to their tive, cumulative, and context-dependent in impact. Some particular context and update their understanding and prac- infl uences may have immediate genetic impacts; others may tices over time as new information becomes available. only exhibit their impacts after many generations. Given the interactions, cause and eff ect may be diffi cult to discern. Planning us, for example, habitat fragmentation may lead to popu- Monterey pine is a conservation challenge. Historically, its lation sizes that are below those adequate to maintain genet- natural range included natural disturbances (e.g., fi re) and ic diversity, which may lead to inbreeding, which may lead was dynamic in its response to environmental change—con- to inbreeding depression, which may lead to loss of seedling ditions that are diffi cult to maintain in urban and semi- recruitment, which may lead to lower population size, and urban environments (e.g., H ). Interestingly, further inbreeding, etc. In this case, most of the steps in the although we restrict the movement of the host species sequence are both causes and eff ects of genetic decline. (Monterey pine), we facilitate the movement of some of its is section has been organized by the general catego- pathogens. erefore, it is important to conserve as much of ries of activity associated with in situ genetic conservation the natural diversity as possible to allow adaptation in situ. of Monterey pine: Planning, in situ management, outreach Amount of genetic diversity is not a suffi cient conser- needs, and research. Within each general category, several is- vation standard in its own right: it must be referenced to sues or activities that are relevant to or appropriate for Mon- adaptability, long-term evolutionary potential, or natural terey pine are discussed. Most, but not all, of these discus- levels and structure. For example, the amount of genetic di- sions include some specifi c recommendations. In a few cases, versity could be increased by genetic contamination, but this the issue or activity is discussed to provide the background is not necessarily a positive contribution. or rationale for other recommendations. For example, some Conserving genetic diversity can be a cost-eff ective man- description of the concept of ‘minimum viable populations’ agement tool in the long term. Healthy, functioning ecosys- is needed to appreciate many of the recommendations relat- tems require fewer inputs on an ongoing basis than stressed ed to in situ conservation. In some cases, the recommenda- ecosystems. Genetic diversity allows a ‘response system’ to tion that pertains to an issue has already been provided in an environmental change. 45 For planning purposes, the defi nition of ‘Monterey pine taneously considered; otherwise known as the minimum forest’ changes according to the intended use. For example, amount of suitable habitat (MASH) necessary for meta- the criteria appropriate for siting in situ genetic reserves will population persistence. us, for a species with presumed diff er from those for buff er areas or seed collections forex metapopulation structure, there are minimally three consid- situ reserves. erations for population size: minimum number of popula- Demographic and genetic characteristics are tightly tions, minimum viable size of each population, and mini- coupled but one cannot serve as a proxy for the other. For mum amount of suitable habitat. e last-mentioned will be example, genetic diversity obviously cannot persist, in situ, necessarily larger than the current occupation of habitat if without regeneration. But simply ensuring regeneration suc- the species is not to become extinct. cess does not guarantee maintenance of genetic diversity. A recent review of models pertaining to MASH for spe- So, for example, encouraging regeneration with mechanical cies with metapopulation structure found that some of the methods may have diff erent genetic consequences than fi re- assumptions in these models were unrealistic, likely leading infl uenced regeneration. to an underestimate—and possibly a severe underestimate— One planning tool for projecting the genetic infl uences of MASH. For example, the assumption that metapopu- of particular activities is to consider the potential impact lations occur at a steady state is probably not realistic for of the activity on the genetic processes of migration (gene many species due to the high rate of habitat loss, fragmen- fl ow), natural selection, and genetic drift. For example, will tation in many landscapes, and lack of opportunities for the activity signifi cantly aff ect pollen production or fl ow, recolonization. erefore, the authors caution that scores seed dispersal, distance between stands of trees, or local of rare and endangered species may already be ‘living dead’, adaptation? committed to extinction because extinction is the equilib- rium toward which their metapopulations are moving in the Recommendation : BiologicallyBiologically signifi cantcant losseslosses ofof geneticgenetic present fragmented landscapes (H et al. ). diversity within the species overall and within each of the fi ve native populations of Monterey pine should be avoided. In situ genetic reservesreserves Because existing parks and other ‘protected areas’ of Recommendation : NativeNative MMontereyonterey pine populations should Monterey pine were neither established nor specifi cally man- not be allowed to become further domesticated, meaning uncou- aged for the purpose of protecting genetic diversity, there pled from natural processes and thus requiring constant input may be a need for additional genetic reserves. e selection and management to ensure standard biological functions such as of genetic reserves is best guided by a knowledge of within- growth and reproduction. population genetic structure, as well as other factors such as potential for buff ers and size required for natural processes Minimum viable population size related to natural regeneration potential. A conventional process involves siting of core reserves, determination of It has been shown, with studies of many diff erent spe- buff er areas, and development of genetic management and cies, that the expected longevity of a population increases monitoring guidelines. An excellent discussion of reserve with its size (H et al. ). Small populations are principles and issues is provided by H et al. (). expected to become extinct rapidly. us, many theoretical However, much of the conventional process may be inap- and empirical studies have attempted to determine the mini- plicable to Monterey pine owing to restriction of opportuni- mum number of individuals required to maintain a popula- ties. For example, although a debate exists over whether it is tion for a given length of time. is concept—minimum vi- preferable, in theory, to have a single large or several small able population size—is useful in risk analysis of population reserves, this may have little application to Monterey pine extinction. is quantity will be aff ected by genetic, ecologi- where large, contiguous genetic reserves are not possible for cal, and demographic features, in particular. L () some or most populations. emphasizes the extreme importance of the demography of e process of selecting genetic reserves for Monterey populations in determining their minimum viable sizes. In a pine may diff er from that used for other more widespread or review of more recent work, N and C () less impacted species in that: conclude that both stochastic demographic models and pop- • Opportunities for selecting genetic reserves may be ulation genetic theory lead to very similar conclusions about severely limited owing to previous loss of habitat, minimum viable population size, at least under panmictic fragmentation of existing habitat, and other land-use conditions. impacts. For species with metapopulation structure, and hence the expectation of local extinctions and recolonizations, a • Opportunities for buff er zones around genetic re- somewhat parallel concept of ‘minimum viable metapopu- serves may be limited in some populations. is may lation size’ has been defi ned as “the minimum number of indicate a need for larger core reserves or possibly interacting local populations necessary for the long-term may be mitigated through creative interventions such persistence of the metapopulation” (H et al. ). Be- as planting buff ers. cause recolonization is so critical to this long-term dynamic, • e loss of considerable habitat and attendant ge- the amount of suitable habitat for recolonization is simul- netic diversity means that the baseline for genetic 46 conservation has been obscured. erefore, a higher- their conservation may be benefi cial to the long-term evo- than-normal retention level for genetic diversity may lutionary fl exibility of the species L( and A be warranted. ). Peripheral populations or individuals—given their • Given the limitations on native populations for mi- edge-of-range conditions and possibility of harboring rare gration in response to climate change by both natu- alleles—may be particularly important in providing the ca- ral (e.g., ocean) and constructed (e.g., urban areas) pacity to adapt to climate change (e.g., G et al. ). borders, reserve sizes should take into account the For Monterey pine, with its few extant populations, this need for adaptation in place. translates to a fi ner scale—peripheral stands and individuals, rather than populations. Additionally, the conservation of • Genetic reserves, in this case, might include some habitat adjacent to peripheral stands and individuals may be potential (new?) habitat for Monterey pine adjacent important to dispersal and colonizing opportunities for this to native populations to allow some freedom of dynamic species. movement, recognizing the movement would most likely be in a north-south direction rather than fur- Recommendation : ‘Outliers’‘Outliers’ (tr(treesees at edges of populations) ther inland. should be conserved because some may contain genetic diversity • ere may be proxies for knowledge of genetic struc- important for adaptation to new environmental conditions and turing: for example, the USDA Forest Service seed may represent opportunities to expand the natural range or al- zones are based on a two-tiered system of physiog- low the populations some movement. raphy and elevation (i.e., don’t move seed between zones). Zones are quite well supported by genetic Information on within-population genetic structure test results. Elevation is usually the more reliable clue should guide the siting of genetic reserves. e size of re- to genetic diff erentiation. serves can be guided by the considerable amount of theo- • Outlying trees may have more value and importance retical and empirical information available. In addition than is the case for many other forest tree species. In to the minimum viable population size discussed earlier, some populations, the outlying trees (on edges of the which gives an indication of population viability over time, forest) may represent adaptations to extreme (i.e., there has been much investigation of the specifi c require- edge of range) conditions and may harbor important ments to maintain genetic diversity in the long term. e genetic diversity. Because of habitat loss, trees near parallel concept, when the primary focus is on long-term the extant edge of the current range may actually genetic conservation, is minimum genetic reserve size. is, represent diversity at a more core position prior to of course, requires the minimum population and habitat habitat reduction. Also, or alternatively, they may sizes discussed above, but in addition considers the amount harbor diversity that is particularly relevant to occu- and distribution of genetic diversity. Generally, the num- pying new environments. ber of trees required for long-term genetic conservation in a population is typically expressed as the ‘eff ective popula- Risk from catastrophic events plays a large role in deter- tion size’ (Ne). is value is not the actual number of trees in mining in situ conservation strategy. A discussion of popu- the population but a smaller, theoretical number based on lation viability theory and evidence from empirical studies the number of unrelated trees, and is aff ected by the mat- concludes that local extinctions—for example, of conserved ing system and demographic profi le of the species. Until populations—are far more common then we would be led recently, a generally accepted rule of thumb for long-term to believe by some prediction models that exclude cata- genetic conservation was that an eff ective population size of strophic events (M and T ). Furthermore,Furthermore, approximately is necessary (i.e., unrelated, random- M and T () suggest that minimum viable pop- ly interbreeding individuals) (e.g., F ; F ulation sizes are almost certainly larger than those predicted and S ; G et al. ). A review of such cal- from a theoretical basis that ignores catastrophes. eir con- culations found much variation in the recommended eff ec- clusion is that even when conserved populations are large, tive population size, ranging from to individuals we should expect local extinctions; they are likely events. (B and M ). In these calculations, there are erefore, conservation plans should acknowledge this and numerous assumptions, including the way genetic diversity include contingencies for catastrophic events. is distributed in the population (e.g., the frequency distribu- tion of rare alleles) and the acceptable level of risk to losing Recommendation : InIn situ genetic reserves should be desig- certain alleles. For example, G () calculated nated for each of the fi ve native populations, guided by within- that individuals would be required to ensure that all al- population genetic structure. ey are critical to genetic con- leles at a locus (i.e., all the alternative forms of a single gene) servation and research objectives. A management plan to guide with frequencies greater than or equal to are detected, the protection of genetic values and a framework for genetic with probability of . monitoring should also be established for these reserves. In the mid-s, the availability of empirical evidence Empirical and theoretical studies show that peripheral and the further development of genetic theory led to the populations are often genetically and morphologically diff er- recommendation that the general rule for eff ective popula- ent from more central populations, and that in some cases tion size should be closer to than (Lande ). 47 is revision was largely related to consideration of the role highly important to the species’ ability to evolve essentially of mutation, and that the potentially adaptive variance is an in place. Monterey pine’s evolutionary history may also sug- order of magnitude smaller than the total mutational vari- gest creative opportunities for genetic (and broader) conser- ance. us, with new information, the desirable size of ge- vation. One such application could be, for example, artifi - netic reserves has recently increased considerably. cially introducing Monterey pine into areas that could have Translating the eff ective population size into a genetic been naturally founded (introduction) had the opportunity reserve size requires insight into how genetic diversity is not been prevented by human barriers or into areas that had structured in the population, demographic structure, physi- been occupied by the species at some earlier time (re-intro- cal distances between trees, and pollen dispersal distances. duction) (e.g., M b). is thought deservesdeserves objec- Generally, the actual or census number of trees required is tive and careful consideration of the risks and benefi ts. Some considerably larger than the eff ective population size. For ex- of the risks include possibilities such as displacing some ex- ample, assume that a reserve ha in size has been proposed. tant populations of other native species, providing an artifi - Using an assumption that trees within a -m radius may be cial bridge for introduced disease (such as pitch canker) into related, it is estimated that this hypothetical reserve might other native species, and aff ecting fi re risk or current distur- contain only eight unrelated trees (Box ). Extrapolating bance regimes in the potential introduction areas. However, to a more desirable number of unrelated trees, we fi nd that there may be considerable ecosystem accommodation, over genetic reserves might be recommended that are consider- time, to such introductions. For example, planted Monterey ably larger than individual existing protected areas in some pines on a southeast facing slope at Muir Beach (north of populations. For comparison, a USDA Forest Service proj- the current northern limit of the natural range of Monterey ect identifi ed potential genetic conservation areas (GCA) pine) serves as an overwintering site for monarch butterfl ies for fi ve commercially signifi cant conifer species: ponder- (T and B ). osa pine, sugar pine, incense-cedar (Calocedrus decurrens), Any such intentional introduction of Monterey pine Douglas-fi r, and white fi rAbiesA ( bies concolor). DependingDepending on would require a case-by-case consideration of the genetic stand conditions and the status and management of adjacent and ecological consequences, not only for Monterey pine areas, recommended sizes of GCAs were from to but also for the new host ecosystem. At present, such his- ha (M b). e shape of the genetic reservereserve is also torical introductions of Monterey pine beyond its native important because it infl uences the opportunities for trees range, into some California state parks and reserves, are to breed with one another, as well as physical considerations considered unfortunate. Indeed, in some parks and reserves, such as shelter of seedlings and windthrow of adults. planted Monterey pines have naturalized and are considered an invasive exotic, competing with the native vegetation. Recommendation : e establishment of in situ genetic re- For example, large numbers of Monterey pine seedlings were serves should be guided by theory such as desirable eff ective pop- planted in the Jug Handle State Reserve (a -ha reserve ulation size. However, given that theory might suggest reserves along the northern California coast in Mendocino County) larger than areas available, eff orts should be made to extend the decades ago, and they have spread by natural regeneration. boundaries of genetic reserves through appropriate genetic man- A large-scale eff ort in the late s removed many of the agement of surrounding urban or recreation areas. trees, but there is still natural regeneration—a condition that will continue until there are suffi cient resources avail- Introduction, reintroduction, or extirpation able to complete the removal (C.M. Fabula, pers. comm.) It of Monterey pine populations is the current policy of the California Department of Parks and Recreation to manage the state parks and reserves not As discussed earlier, the dynamic evolutionary history only in a manner that would maintain and encourage na- of the species and sensitivity to climatic triggers, combined tive species, but to match the local gene source for planting with the current limitations on the movement of Monterey stock. Consistent with this policy, exotics—including Mon- pine, suggest that maintenance of genetic diversity may be terey pine planted outside its current natural range—are removed to the extent possible with the resources available for such activi- Box . Genetic sampling for ex situ or in situ reserves:reserves: ties (S.R. Bakken, pers. comm.). us, How much is enough? intentional introductions of Monterey pine, or maintenance of existing natu- “I C- there would be only about eight unre- fornia we collected in fairly dense forests lated trees in each of the proposed -ha ralized plantings, would not only have from trees about m apart to be sure reserves, and for the whole popula- to be well considered, but negotiated we were not collecting from closely re- tion, a small number, but far better than and rationalized within the appropriate lated trees. After an old tree is killed in having no secure reserve. Of course there management structure. a wild fi re most of the seed falls near the would be many other trees in each re- Another and more conservative tree so that a family group is established serve and they would also contribute to approach to conserving and possibly in an area perhaps m diameter, and genetic conservation, as well as to æsthet- expanding the species range is conser- one group overlapping with the next to ic and habitat values.” (K.G. Eldridge, vation of areas adjacent to the extant some extent. By that sampling standard pers. comm.). populations to allow movement via 48 natural regeneration. Indeed, some recent conservation ac- (S et al. ). Certainly,Certainly, degraded or fragmented for- tivities embrace this view by protecting areas adjacent to est ecosystems are less resilient or resistant to climate change Monterey pine forests in addition to the current forested eff ects than are diverse and healthy ecosystems N( ). area (e.g., recent conservation easements, conservation man- Minimally, these climatic changes will provide diff erent agement agreements, and land purchases in the Cambria or more pronounced selection pressures on populations of area). Monterey pine. In particular, climate may be expected to af- e rationale for founding new Monterey pine popula- fect its phenology. Possibly, the changes would be suffi cient tions is strengthened by, although not entirely dependent to decrease current habitat. Prior to human settlement, spe- on, embracing the concept of metapopulation structure for cies theoretically would have had opportunities to migrate in this species (see Box ). Metapopulation structure would in- response to climatic pressures. However, given the develop- clude not only natural occurrences of new populations being ments and land uses surrounding Monterey pine habitat, founded but of existing populations going extinct (i.e., extir- this is not an option in most areas. In situations such as this, pation). One must be careful, though, not to make illogical where the species cannot avoid an increasingly stressful envi- applications of our understanding of the species’ evolution- ronment by shifting its geographic distribution, adaptation ary history. For example, local population extinctions that or extinction will rely decisively upon the ability of the spe- may have happened over evolutionary time scales should not cies to mobilize suffi cient genetic variation to track the envi- be encouraged or viewed as normal species’ dynamics within ronmental change (R-T et al. ). our human time scales. Obviously, the loss of populations e potential to adapt to strong directional selection, over evolutionary time in response to climatic triggers when such as that imposed by rapid climate change, could be lim- the species has many populations and is recolonizing is a ited either by limitations in the amount of genetic diversity very diff erent situation from the present—where the spe- (i.e., additive genetic variance for selected traits becomes cies is reduced to a few populations (S.P. Harrison, pers. exhausted) or because of counterbalancing selection by comm.). other infl uences R( -T et al. ). Both the amount and the structure of genetic diversity will infl uence Climate change the capacity of a species to adjust to environmental stress as- Temperatures rose in the th century at a rate unprec- sociated with climatic warming (G et al. ). GivenGiven edented in the last millennium. Atmospheric CO concen- the evolutionary history of a dynamic natural range that is tration is now higher than at any time in at least the last responsive to climatic triggers, and a current natural range years and it will almost certainly double within that is highly constrained by development, it is critical that the next century (B ). Changes in the normal the genetic diversity of Monterey pine should be conserved range of temperatures, patterns of precipitation, concentra- so as to allow continuing evolution in place (in situ). e tion of CO, and other atmospheric characteristics aff ected predicted eff ects of rapid climate change underscore the by recent and continuing climate change, will aff ect forest need for maintaining diverse gene pools and avoiding fur- dynamics and possibly species’ ranges (e.g., P ). ther forest fragmentation (N ). Globally, these eff ects are expected to be more pronounced in temperate (including the Monterey pine native range) Ex situ genetic conservationconservation and arctic forests, where temperature increases are projected Ex situ genetic collections are important not only as a to be relatively large. Coastal ecosystems may be more im- parallel conservation strategy to support in situ conservation, mediately and critically aff ected, given that global mean sea but also for research, education, and commercial breed- levels are expected to rise about cm per decade (K ing activities for industrial plantations in other countries. et al. ). Given that climate change will surely exert sig- G and P () summarizesummarize factors germane to nifi cant pressures on Monterey pine, that its precise envi- genetic sampling for conservation collections of endangered ronmental tolerances are not known, and that historical mi- plants. Monterey pine has attributes corresponding to eight gration routes for populations are largely limited by human of the ten highest priority criteria for genetic sampling (e.g., developments, it is desirable to conserve as much extant experiencing rapid decline, biological management required, genetic diversity as possible to allow the best opportunity for recently or anthropogenically reduced, feasibility of success- adaptation in place. ful maintenance in cultivation or storage, and economic Predicting the eff ects of climate change on ecosystems potential). It is desirable to conduct further rangewide col- is complicated and requires baseline data on the status and lections of Monterey pine seed from the fi ve natural popula- trends of a vast array of species across all taxa, and eff ects tions. ere is some urgency to this because of the attrition may diff er across spatial scales and with the assumptions of old trees on Guadalupe Island and the recent mortality about the nature of climate change (R and S within the California populations from pitch canker that ; B et al. ). In one study, future species may remove some signifi cant genetic diversity. In response distributions were simulated for a future climate scenario to the concern about loss of genetic diversity in the pines (–, -year mean) for tree and shrub species in on Guadalupe Island, a multinational expedition was orga- North America (including Douglas-fi r and ponderosa pine). nized and seeds were collected on this island and on Cedros Predicted range shifts were in all directions (i.e., not simply Island in May for conservation, possible restoration, northward) and characterized by increased fragmentation and research purposes (Box ). Care must be taken to collect 49 seeds at a time that coincides with maturity and maximum be completely replaceable because the genetic source may viability of the embryos (e.g., R et al. ). be gone, depleted, or contaminated. erefore, it is impor- Collections may at least provide a reservoir of some of this tant to treat ex situ collections as valuable and fi nite. Use of diversity to be used at a later time for regeneration, restora- these collections should be guided by a policy that consid- tion, research, or other purposes. Additional seed collections ers the value of the proposed use and the benefi ts and risks are also warranted as seeds have fi nite lifetimes (i.e., one of of reducing the ex situ collection for this purpose. Some uses the most comprehensive and rangewide collections is now of genetic collections are nonconsumptive (e.g., educational years old) and former seed supplies have been diminished activities such as tours of breeding orchards and genetic fi eld through use. Also, existing seed collections do not neces- tests). Some parameters that could be considered in mak- sarily represent the range of genetic diversity. For genetic ing decisions about the use of limited genetic collections are research that could off er more scientifi c information towards presented in Table . conservation, additional seed collections can off er the op- Financial support is often a limiting factor in long-term portunity to study specifi cally the pattern of genetic diver- conservation of ex situ genetic collections. Genetic collec- sity in each population. tions are particularly concentrated in the public sector and are disproportionately aff ected by government cutbacks in Recommendation : AdditionalAdditional seed collections budgets. e true value of genetic collections has not been should be undertaken in the fi ve native popula- tions using genetic sampling criteria. Table . Factors to consider in deciding appropriate use of ex situ genetic collections† for research or restoration purposes. Given the value of ex situ collections Factor for research, education, conservation, and commercial activities, their viability should Type of use Favoring use Against use be supported with the best available facili- General ties and professional stewardship. Emerging Use is nonconsumptive Use is consumptive technologies and information from recent studies should be routinely evaluated for Collection easily replaced Collection wholly or relevance to the maintenance of collections partially irreplaceable (e.g., S and S ). Although Collection inexpensive to Collection very expense to seeds of temperate zone pine species typically replace replace have good long-term storage capability, there can also be losses in viability over time and Multiple uses/applications Restricted use/application genetic changes due to chromosome damage Specifi c research or nonrandom loss of seed viability (B Research is novel Research not novel ). e physiological condition of the seeds when stored and the storage conditions Methods are parsimonious in Methods unnecessarily also infl uence the shelf-life of seeds. Research germplasm use consume germplasm on long-term storage for Monterey pine Objectives require specifi c Objectives could be satisfi ed seeds, including cryogenic storage, could genetic material with less valuable genetic provide valuable enhancement to the role of collections or de novo seed collections in genetic conservation. collections e status of ex situ reserves of Monterey pine in California should be determined, Outcome likely to support Research has little to no including recommendations for maintaining conservation of in situ conservation application the conservation values of the various seed populations collections and outplanted reserves. Seed Germplasm or DNA products Germplasm completely collections, for example, can vary consider- can be reused for other consumed or contaminated ably in their value for conservation purposes, purposes depending on the sampling design for the collection and the seeds’ viability. Old or Conservation/restoration even nonviable seed collections could still be Natural regeneration unlikely Natural regeneration still useful. For example, some types of genetic possible research can make use of DNA from seed that have lost viability and are not of use for Little risk of genetic Signifi cant risk of genetic restoration purposes. contamination of natural contamination of natural Given recent or potential signifi cant populations populations losses in genetic diversity within the na- †It is assumed, for the purposes of this table, that the genetic collections are pure tive Monterey pine populations, existing ex collections (i.e., refl ecting the genetic attributes of the native gene pools, without situ collections of Monterey pine may not contamination), still valuable for restoration or native-population research purposes. 50 calculated or internalized in activities—such as research— For example, some pines near the Carmel River were felled that make use of them (e.g., H ). To mitigate and used in establishment of the Carmel Mission in . this problem, pricing schedules could be developed to sug- During the mid-s, other documented uses of Mon- gest fi nancial contributions by researchers who use genetic terey pines were the building of a fort and blockhouse near collections of Monterey pine. ese expenses could become Monterey, the export of timber to the Hawaiian Islands, normalized in research proposals. and the establishment of a sawmill near Point Cypress that Other than seed collections, Monterey pine genetic col- rapidly thinned out the forest. Brick kilns established in lections exist in various genetic trials, breeding orchards, and the area also promoted harvesting because of the need for other living collections in California. Often established in fuel (MD ). is historical use of much of the the s and s, they require a current and focused as- Monterey population may have had an impact on genetic sessment because of changes over the last few decades that diversity. Without an unharvested, natural forest stand in include introduction of pitch canker, changes in principal the area with which to compare, it is diffi cult to assess the researchers and staff associated with these collections, chang- genetic eff ects of harvesting practices. However, a recent ing priorities or emphases in the host institutions or compa- comparison of genetic diversity in old-growth populations nies, and changing requirements of the genetic collections of eastern white pine (Pinus strobus) with partiallypartially harharvestedvested due to their age (e.g., aging seed collections or mature seed nearby stands provides some insight. Pre- and post-harvest orchards). genetic diversity were measured in each of two study ar- eas—approximately . ha each in size—within larger areas Recommendation : ProtocolsProtocols for any extant ex situ genetic of old-growth eastern white pine. In this study—conducted reserves should: in Ontario, Canada—genetic erosion occurred as a result of harvesting. e total and mean number of alleles were re- i. Determine the maintenance strategy for that collection, duced by approximately , the percentage of polymorphic including risk management by subdividing the collec- loci dropped by about , and about of the low-fre- tion among several location; quency alleles and of the rare alleles were lost because ii. Recommend and preferably secure a long-term or per- of harvesting. is suggests that the ability of the posthar- petual sponsor or steward for the collection(s); vest gene pool to adapt to changing environmental condi- iii. Establish priorities for the most appropriate use of the tions may have been compromised (B et al. ). collection (i.e., decision-making criteria for seed distri- Given the historical harvesting practices that occurred bution for uses such as research, commercial, restoration, throughout much of the mainland California populations or mitigation); and of Monterey pine, care must be taken in describing ‘natu- ral’ levels and structure of genetic diversity. Knowledge of iv. Recommend a pricing structure for returning support to management history is needed to make decisions about site the collections based on their use. selection for research and for context in interpretation of sci- In addition to these considerations, plans for any future genetic entifi c studies involving the current Monterey pine forests. collections should include an assessment of the eff ect of the col- lection on the genetic diversity of the sampled natural popula- Recommendation : Management history, for the mainland tion (e.g., risk assessment). populations in particular, should be well documented to allow appropriate site choices and data interpretations for scientifi c In situ management research and for support in forest management. Harvesting infl uences Habitat loss and fragmentation Historical harvesting practices, at least on the mainland Loss and fragmentation of the natural habitat of for- of California, have aff ected habitat of Monterey pine and est tree species have been so long term and widespread that probably its genetic composition. Several cycles of logging there is considerable theoretical and empirical evidence of over much of the pine forests of Cambria and Monterey, in the signifi cant genetic impact for some species (e.g.,L particular, occurred in the s and s. e Año Nuevo ; H and H ). Reduction in the natural population was perhaps less aff ected by logging owing to the range of Monterey pine provides two physical consequences availability of coast redwood and Douglas-fi r in that area. which, in turn, could precipitate genetic consequences: loss Although all harvesting does not necessarily have a negative of habitat at the margins of the existing populations increas- genetic impact, it can be detrimental if it is extensive and es the distance among populations; loss of habitat within causes narrowing of the genetic base in future generations populations can cause fragmentation. Both types of habitat or if it is selective of certain trees which carry genes that are loss can change the pattern of pollen and seed dispersal (and absent or less frequent in the remaining trees. Good reviews their effi cacy) and gene fl ow. For example, fragmentation of of the human settlement activities and logging practices in forest populations can create habitats that promote interspe- these areas are provided by F () and L (). cifi c hybridization (e.g.,H ). e genetic con- Much of the Monterey pine forest in Monterey County sequences of fragmentation depend on the breeding system has been harvested at least once (e.g., MD ). and type of pollination (e.g., N and H ).
51 Estimates of a tree population’s mating system (rates of self- versity and remove locally adapted subpopulations (L versus outcross-fertilization) and breeding structure (spatial ). Although the within-population genetic structure of patterns and relative frequencies of eff ective pollen transfer Monterey pine is not well studied, suggestions of fi ne-scale between plants) are also indicative of pollen dispersal pat- structure are evident in a number of studies. C et al. terns (N and H ). () noted diff erences in salinity tolerance among sub- Fragmentation can lead to other eff ects, indirectly aff ect- populations of the Monterey population. T et al. () ing genetic diversity and structure. Fragmentation creates found diff erences in six-year volume among subpopulations more forest edge which can alter the sunlight and wind ef- within mainland populations. B et al. (a) found fects on the forest fragment (relative to the former contigu- that one subpopulation from Año Nuevo grew much more ous forest), which can, in turn, aff ect forest structure, leaf slowly than the seedlots collected from other areas within fall, turnover in the plant community, seedling recruitment this population. J et al. () found signifi cant dif- patterns, and distribution of animals (G et al. ). ferences in height and basal area among some subpopula- In some studies of tropical forests, fragmentation has had tions within mainland California populations. major impacts, very quickly changing the tree composition from climax to pioneer species, and a cascade of associated Recommendation : FurtherFurther frfragmentationagmentation of rremainingemaining MMon-on- impacts (G et al. ). terey pine forests should be avoided. Although the naturally occurring distance among popu- lations and the genetic substructuring within populations can enhance genetic integrity because they may refl ect un- Fire suppression derlying processes such as adaptation (e.g., C ), e role of fi re in Monterey pine forests may change forced distance or fragmentation—such as that caused by over time, is dependent on the nature of the fi re, and is af- housing or transportation developments—can have detri- fected by interactions with climate and other environmental mental eff ects on genetic integrity by interrupting these pro- and anthropogenic factors. Both social and ecological con- cesses. Fragmentation may lead to artifi cially small subpopu- texts are important considerations for management of Mon- lations which may increase the eff ects of genetic drift—the terey pine forests as it pertains to fi re policy. For example, in random process of gene sampling from one generation to areas where Monterey pine intermixes with knobcone pine, another. Small populations tend to lose genetic variation fi re may be given more ecological weight in management by genetic drift more rapidly than will larger populations. decisions because of the more intense heat required to open In fact, a study comparing the eff ects of such processes as the cones of knobcone pine (V ; S ; O- genetic drift, mutation, immigration from outside popula- and N ). Given the urban and near-urban tions, and directional and balancing selection, revealed that location of much of the remaining Monterey pine forests on genetic drift was the overriding factor controlling the loss of the California mainland, suppression of wildfi res is likely genetic variation (L ). ese resultsresults werewere interpretedinterpreted to continue in many areas. Public safety and protection as a strong signal to managers that they should be concerned of buildings and other developments are one issue; pub- with the variation-depleting eff ects of genetic drift. lic acceptance of this natural disturbance and its ecological Reduction of population size or increasing the distance impact is another. For example, after the ‘Vision Fire’ (i.e., among populations can have signifi cant genetic consequenc- a massive wildlife ignited by embers of an illegal campfi re es. ese trends may result in increased levels of inbreeding on October , on Mount Vision in the Point Reyes which genetic theory indicates may result in expression of National Seashore in Marin County, California), there was deleterious recessive alleles which may cause lowered fecun- prolifi c natural regeneration of bishop pine, and many of the dity, higher seedling mortality, and reduced growth rates pine trees in the previously mature pine forest were killed that could eventually drive a population to extinction (e.g., (O and N ). Although this may be consid- W ). As discussed earlier, there is considerable evi- ered a natural regeneration cycle, the dramatic change in the dence of vulnerability to inbreeding depression in Monterey landscape and abundance of charred dead trees may not be pine. Also, loss of heterozygosity (another consequence of immediately understood and accepted by the public. inbreeding) may reduce a population’s ability to respond to Although the relationship between historical fi re regimes future environmental changes—thereby increasing the prob- and Monterey pine seed production, seed dispersal, and ability or rate of extinction (e.g., F ). Examples seedling establishment and recruitment is not well under- of the consequences of extreme reduction in genetic diver- stood, the reality of fi re suppression (for reasons of safety, sity are found in agriculture. Early th century Irish farmers investment protection, or public sentiment) has generated mostly grew a single clone of potato—a clone that proved interest in fi nding substitute treatments for fi re infl uence. vulnerable to the devastating potato blight. Similarly, by One treatment that has been tried in some forest situations , of the United States’ corn crop was composed of to enhance regeneration in the absence or near-absence of a single genotype that was vulnerable to the corn blight fun- fi re (and where fi re was a part of the landscape prior to hu- gus (L ). man infl uence) is mechanical creation of gaps or openings Loss of habitat within populations—those fi ve major in the forest canopy. is treatment might be particularly areas of Monterey pine that we superfi cially call popula- eff ective in situations where shading, because of a mature tions—may actually erode signifi cant levels of genetic di- and closed canopy, is a major limiting factor in germination 52 or seedling establishment. If other factors are limiting, this for example, pollen production from the contaminant trees treatment may not be eff ective. For example, a study of the is very large, it can ‘swamp’ the proximate native forests. eff ects of harvesting trees to create openings in a giant se- In the second case, even if the contaminant source is well quoia forest near Mountain Home, California revealed that matched genetically (i.e., it is from a local source), a kind of these mechanically created gaps were not successful—in this genetic contamination occurs if the genetic diversity of the situation—in stimulating natural regeneration. is har- native forests is lowered or changed by the overrepresenta- vesting practice attempts to simulate the natural fi re regime tion of certain genes (alleles) in the introduced trees. For ex- of forests (in this case, the southern Sierra Nevada mixed- ample, if a local seed source was used to produce a clone that conifer forest), but important ecosystem processes such as was then planted in large numbers close to the native forest, increased seed dispersal following patchy, high-intensity fi re its reproductive output could decrease the genetic diversity in and large-scale nutrient cycling are not duplicated with me- the forest over time and cause inbreeding depression. chanical treatments (S et al. ). e third case—that of genetic mismatching—is the In addition, the genetic impacts of using mechanical conventional condition for genetic contamination. In theo- rather than fi re- or other-stimulated regeneration are not ry, genetic contamination can undermine fi ne-scale genetic known. An intense fi re could simultaneously open the cano- structure and adaptation to local conditions. is potential py for light penetration to the forest fl oor, release abundant has been demonstrated empirically for some woody Califor- seeds by opening cones, and remove much vegetative com- nian species, including the subshrub Lotus scoparius, where petition (for moisture and nutrients) for the Monterey pine transplantation experiments showed lowered fi tness for ge- seedlings. For example, in the absence of fi re, forest con- netically mismatched populations, consistent with disrup- version to a more oak-dominated forest has been noted in tion of local adaptation (M and E ). some areas (MB and S ; W ). ere ere can be a range of eff ects, depending upon how diff er- could be abundant, even-aged regeneration after such a fi re, ent or ill-adapted are the foreign genes and how they inter- which could allow a broad palette on which natural selec- act with resident gene pools. For example, if the introduced tion could act. In contrast, regeneration events that are more genes were directly expressed and very maladapted to local scattered, gradual, or lower intensity, would change the se- conditions, the seeds or seedlings might die soon. In this lection regime and potentially change the diversity, density, extreme case, the genetic contamination is self purging, over and dynamics of fi re-related regeneration. ese diff erences perhaps as little as one generation. However, there is still an in regeneration dynamics, and selection regimes, have po- ill eff ect in that the regeneration opportunities (within lo- tentially signifi cant consequences for the genetic diversity of cal gene pools) have been temporarily lost or compromised. subsequent generations of Monterey pine. Another scenario is that if the local population is inbred, In summary, whether or not fi re is needed for regenera- outcrossing to a nonlocal source may lead to heterosis and tion of Monterey pine is not the key question. Rather, we genetic contamination may persist over several generations. need to understand the interrelationship of fi re with the More likely, the introduced genes have a less dramatic im- ecology, reproduction, recruitment, and long-term health of pact and may remain permanently in the population, con- the species and its ecosystem. at information will then in- tributing to future generations and probably lowering the form forest managers as to whether and how other manage- fi tness of that population to some extent, depending on how ment options can simulate the eff ects of fi re where its direct fi ne-scale are the adaptations to local conditions. use is impractical. In general, more research is needed to A committee formed to evaluate introduction of exotic understand regeneration dynamics. genotypes into the University of California’s nature reserves has outlined a number of documented eff ects from the sci- Genetic contamination entifi c literature of such nonnative introductions E( Genetic contamination, simply, is the introduction of et al. ). ese eff ects include: disruption of natural pat- foreign genes into the local populations. In this usage, ‘for- terns of geographic variation in genotype frequencies (which eign’ refers to genes from nonlocal individuals of the same in turn aff ects the suitability of nature reserves as study species. is can occur directly—by planting seedlings from areas for natural populations), introduction of genes that a nonlocal source in the local populations, or indirectly— are poorly adapted to local conditions, disruption of local from pollen or seeds blown in from sexually mature trees of patterns of gene interaction, potential to aff ect the popula- nonlocal origin that were planted close enough to the native tion’s future ability to respond to environmental change, and populations to infl uence them. cascading eff ects through the community (i.e., any genetic In general, the scope and impact of genetic contamina- changes that alter a given species’ ecological properties are tion will derive from three conditions: the size of the ‘con- likely to be felt in the community). Some or all of these ef- taminant’ source relative to the native forests, the genetic fects are potentially applicable to the Monterey pine forests. diversity of the contaminant, and the degree of genetic e opportunity for genetic contamination varies with matching between the contaminant and the native forests time and conditions. Proximity of introduced trees to na- within gene fl ow range. In the fi rst case, the larger the num- tive trees is a large determinant. However, the transport of ber of contaminant trees, and the greater their reproductive pollen, for example, will vary from year to year and among output (i.e., seeds or pollen) relative to that of the native for- pine populations in relation to weather and topography. est, the greater is the potential for genetic contamination. If, e annual variations may be more important in the early 53 stages of pollen production in a stand (R.D. Burdon, pers. apparently were planted close to Asilomar State Beach and comm.). Wind force, temperature, and humidity are key en- the Spanish Bay native stand (L ). vironmental factors infl uencing pollen dispersal F( Genetic contamination could also result from planted a). Studies of the reproductive biology of Monterey pine fi eld trials,ex situ reserves of Monterey pine, or Christmas (outside its natural range) suggest that there is considerable tree plantations if nonlocal trees in these collections reached individual-tree and yearly variation in amount of pollen pro- sexual maturity and were within pollen fl ow distance of na- duced, timeframe for pollen dispersal, amount of seed dis- tive populations. e extent and severity of genetic contami- persed, and dispersal distance (e.g., F ). nation has not been studied comprehensively, either indi- e importance of using local plant sources to avoid rectly with a survey of planting records or by genetic testing genetic contamination has been recognized by the Cali- of planted trees or directly with observation of genetic con- fornia Department of Parks and Recreation. Charged with tamination in native forests. the responsibility for protecting and preserving the State’s Many California Christmas tree growers use nursery natural heritage, the Department has a policy that specifi - stock derived from New Zealand sources. However, genetic cally refl ects the requirement to protect the genetic diversity contamination from this use of Monterey pine has probably of the State’s rich botanical assemblage. Policy Number of not been extensive, based on current conditions and prac- the California State Parks and Recreation Commission states tices within the California Christmas tree industry. First, that “In order to maintain the genetic integrity and diversity genetic contamination would only be a potential issue when of native California plants, revegetation or transplant eff orts Christmas trees are grown within the pollen range of the in the State Park System will be from local populations un- native Monterey pine forests, thus excluding many current less shown by scientifi c analysis that these populations are growers. Second, depending on the age at which trees are not genetically distinct from populations being proposed for sold, pollen contamination may not be a signifi cant issue. use.” (W and H ). Based on the generally fast growth of farm-grown Monterey Because of the decades-long use of Monterey pine as an pine, they are often sold at three to four years of age, and urban landscape species and as roadside screens in coastal not generally older than six years, even when grown on poor California (Box ), there has been considerable opportu- sites (S.E. Minturn, pers. comm.). Finally, another potential nity for genetic contamination to occur in the three main- source of genetic contamination—that of people planting land populations. In fact, by the early s it was noted living Christmas trees in or near the native Monterey pine that pollen and seeds were invading the native stands from forest—has a very low likelihood of signifi cant genetic eff ect. widespread roadside and amenity plantings in the increas- is is because the market for live Monterey pine Christmas ingly urbanized Cambria and Monterey native populations. trees is very modest, probably not more than a few hundred ese plantings were often Monterey pine seedlings from trees annually (S.E. Minturn, pers. comm.). unknown or uncertain sources, or from known nonnative sources (L ). InIn the city of Carmel, at the edge of Recommendation : e genetic and associated demographicdemographic the Monterey area population of Monterey pine, over risks from planted Monterey pines (e.g., roadside plantings, of the city tree population is composed of Monterey pines— landscape trees, residential trees, and Christmas trees) within many planted by city personnel and of uncertain genetic ori- the current reproductive range of native Monterey pine popula- gin (N and MB ). Nonlocal Monterey pines tions should be evaluated. is evaluation should include an ex-
Box . Planting of Monterey pine along California highways.
A C (C- ies and some, if not much, of the mate- that, Monterey pine was planted along fornia Department of Transportation) rial may have come from New Zealand coastal highways, including State Route personnel found that records were not or Australian sources. To the extent it is and US , with a total in the thou- suffi cient to determine the seed source, derived from New Zealand sources, the sands. e range of plantings on Caltrans nursery location, or year of planting for planted seedlings would very likely con- right-of-way areas has been from Ventura/ all projects within their considerable tain a signifi cant portion of Año Nuevo Oxnard northward through the Bay Area planting program of Monterey pines ancestry (R.D. Burdon, pers. comm.) Re- and as far inland as the Coast Ranges and along California highways (D.T. Grin- search strongly indicates that the source in the Salinas Valley. Some particularly stain, pers. comm.). material that forms the foundation of dense plantings exist along State Route It is not known when pines were fi rst New Zealand commercial stock derives in the area between Monterey and Car- used by Caltrans along transportation from only Año Nuevo and Monterey, mel. Here, it had been recommended to corridors, but revegetation has been a part with a disproportionate contribution plant seedlings with a close spacing be- of the department’s activities since shortly from the former (B ). cause of the expectation of high mortality. after its organization, approximately Because of increased mortality, largely Many of the pines survived, however, and years ago. erefore, some of the planted from pitch canker, Monterey pine is no today provide a dense cluster of adult Monterey pines may be quite old. longer planted by Caltrans and has not trees (D.J. Reeves, pers. comm.). Planting stock was obtained, through been a regular part of their revegetation contract, with a variety of private nurser- program for at least seven years. Prior to
54 amination of geographic scope, timeframe over which trees have satisfi ed in certain areas with knobcone or bishop pines. As been planted, and genetic source of material. has been documented elsewhere in this report, naturally oc- curring hybridizations between Monterey pine and bishop It is desirable for many applications to be able to de- pine have been observed at Monterey at low frequencies termine the geographic and genetic origin of planted trees. (less than one percent of the population, noted in the s; When this is not possible via records, some investigations S ). Similarly, a modest number of natural hy- have determined the feasibility of using various molecu- brids of Monterey and knobcone pine have been noted near lar markers for this purpose. For example, using allozyme Point Año Nuevo in Santa Cruz County (L ; frequency data, M and B () determined that S ; B ). Historically,Historically, thertheree has been Monterey and Año Nuevo populations are most likely the some seasonal separation of phenology (i.e., pollen is shed major sources of original introductions in Australia. e ori- later in knobcone pine and bishop pine than in Monterey gin of Basque populations of Monterey pine were investigat- pine), at least in these areas, which has perhaps prevented ed with RAPD markers. Results indicated that the Basque more recruitment into the population from these interspe- populations are most probably derived from the Año Nuevo cifi c hybrids. As these are natural occurrences, this would population (AA et al. ). However, there was no not constitute a genetic threat unless conditions changed estimate of the power of the test. ere is also the issue here such that interspecifi c hybrids were becoming much more of sample size. Determining the origin of a large sample of common and replacing the pure species to a large extent, or trees, knowing a priori that all areare of the same origin, is a if planted knobcone or bishop pines were contributing inter- diff erent and easier question than determining, with cer- specifi c hybrids to the native populations. Outside of natural tainty, the origin of an individual tree. S et al () occurrences, there has been considerable breeding and test- could diff erentiate among the fi ve natural populations using ing of artifi cial crosses between these species (Box ). mitochondrial DNA RFLPs. Nuclear microsatellite markers have been developed for this species (e.g., S and D Mitigation-, urban-, or recreation-related ; F et al. ) and, because they showshow a high levlevelel planting of Monterey pine of polymorphism and Mendelian transmission, they may be Genetic conservation concerns related to the planting useful in providing population identities for individual trees. of Monterey pine outside the natural forest depend fi rst A technology that is being developed for application in on whether or not the planted pines are within the seed commercial plantations of Monterey pine could have rel- dispersal and pollination region of natural forests. If so, evance to the reduction of genetic contamination of native then much of the rationale concerning planting is based on Monterey pine forests. is technology is the generation of choice of material that does not constitute genetic contami- reproductively incompetent trees through genetic engineer- nation risk. If not, then planting decisions are wisely guided ing. e advantages of this characteristic in commercial by the arboricultural considerations including growth rate, forestry include direction of more energy by the trees into growth potential, light regime available and desired, soil vegetative growth, control of the invasive nature of the pines type, disease vulnerability, leaf fall or retention, and proxim- in some situations and hence less management directed ity to structures. towards removal of volunteer seedlings, and expansion of When planting Monterey pine trees close enough to the the range of plantation possibilities into residential areas natural pine forests such that it can reasonably be expected without attracting criticism from those concerned about the that seeds or pollen from the planted trees could mix with potential for pollen-related allergies (M and T- those of the forest when the trees are sexually mature, genet- ). Although this technology has not been fully ic implications should be considered. In addition to genetic developed for Monterey pine, the potential has been fully contamination issues, discussed earlier, other genetic consid- demonstrated with the isolation and characterization of a erations are maintenance of natural levels of genetic diversity gene family showing specifi c expression in immature male and local adaptations. and female cone buds (M and T ). It is particularly important to consider genetic appro- Near natural populations of Monterey pine, this technology priateness when planting Monterey pines in areas where the could allow the extension of the ecological perimeter of the boundaries between native forest and domesticated trees are forest with Monterey pines that have specifi c characteristics not well defi ned. e reason is not only the high potential of value to urban settings (e.g., pitch canker resistance or for genetic contamination of the native forest, but the con- desirable shape) without presenting a genetic contamination fusion this presents for defi ning areas for conservation or for threat. research on natural pine populations. Memories and records An issue related to genetic contamination, but not con- tend to deteriorate over time, lending to confusion over sidered here to be a genetic threat to the species, is inter- what is natural and what has been introduced. Given the breeding with other pine species—known more technically limited availability of natural buff er areas for current or fu- as introgressive hybridization. As with other species, this can ture conservation reserves of Monterey pine in some popula- only occur where two sexually compatible species grow close tions, the close vicinity and high level of interdigitation of together and where the habitat allows an ecological niche for natural and urban areas in the Cambria and Monterey pine the establishment of the introgressive hybrids (e.g., S- populations in particular, the potential for large numbers of ). For Monterey pine, these conditions are both planted trees over time, and the potential for confusion over 55 planted versus natural trees in the long term, it is important losing some genetic diversity that is associated with vulner- that planted Monterey pines are genetically appropriate for ability to the infl uence. With coevolved biotic infl uences the area. is includes street and residential plantings, miti- (e.g., native insects and diseases), there is an evolutionary gation plantings, artifi cial regeneration eff orts, and restora- history that has resulted in some type of interaction that has tion activities. allowed both species to persist. With introduced organisms, no such mechanisms are necessarily present and epidemics Recommendation : ForFor any planting of MMontereyonterey pine with- may result. A case in point is white pine blister rust (caused in an area where mixing with the native gene pool is possible, by Cronartium ribicola). Introduced to western North Amer- the planting stock should be locally adapted and contribute ica in , its impacts have resulted in one of the most cata- to maintenance of natural genetic diversity of the native pine strophic plant disease epidemics in history (K and forests. Seeds should be preferred to seedlings. Clonal material D ; K ). should not be used except in limited scope in situations where Responses to artifi cial selection or human-induced fac- this is the only feasible or well-reasoned alternative. For large tors (e.g., introduced diseases) may not follow the same planting projects, the source for propagules should be chosen so ‘adaptive model’ as natural selection. Comparison of the as to create a large eff ective population size. results of some empirical studies demonstrates that specifi c empirical studies for the species and adaptive characters of Introduced biotic infl uences interest are required to understand the genetic basis of the specifi c adaptation O( and I ). Introduced biotic infl uences, such as diseases or insects Over endemic diseases and insects have been de- that have evolved outside the native range of the host spe- scribed for Monterey pine (O ; O , cies, may have two types of genetic impact. If they have ; O , ; O and V ; O et al. major eff ects on mortality or reproduction in the host (i.e., ), but these natural infl uences are part of a functioning Monterey pine), they can reduce genetic diversity generally. ecosystem and natural selection regime rather than a threat If there is some genetic basis for resistance in the host then to the genetic diversity of the pine. However, introduced there can be selection within the pine populations, thereby biotic infl uences may have a negative impact. For example,
Box . Artifi cial interspecifi c hybridization of Monterey pine.
I USDA F S tions, it was determined that the hybrids to snow damage (R.D. Burdon, pers. began an interspecifi c crossing program morphologically resembled knobcone comm.). Superiority in cold hardiness of for pines with the practical purpose of pine more than would be expected. It the hybrids was also noted in AFOCEL producing promising hybrids for exten- was suggested that this may in part be studies conducted near the Bourdeaux re- sive testing in forest plantings. Monterey due to maternal eff ects H( ). gion in France (F.T. Ledig, pers. comm.). pine has been hybridized artifi cially Interspecifi c crosses, advanced genera- e California Department of Forestry with knobcone and bishop pine, among tions, and backcrosses from these two and Fire Protection (CDF) has collaborat- other species (e.g., Righter and Duffi eld species in cultivation at Placerville were ed in producing controlled crosses, using ). Hybrids between knobcone and analyzed for turpentine composition and pollen collected from knobcones in the Monterey pine produced in nursery the results suggested that the diff erence in Santa Cruz area and pollinating Monterey conditions have proven vigorous and turpentines of Monterey and knobcone pines growing in the Forest Service’s Bad- fertile (S and R , pines was controlled by a single gene, ger Hill Breeding Orchard. Seedlings from R ). Characteristics of the inter- with probable modifi ers in Monterey pine a specifi c cross (known as ‘KMX’) were specifi c progeny relative to the parental (F a). installed in fi eld tests in various counties species are described in S and e knobcone × Monterey pine hy- in California (including San Bernardino, R (). InterspecifiInterspecifi c chybrids hybrids brid has also shown potential for use in Humboldt, and Trinity) to observe long- between bishop and Monterey pine could reclamation of some disturbed areas in term growth characteristics. Preliminary have some interesting traits, depending California. Experiments with various observations from some of these tests sug- on which seed sources were used for the tree, shrub, and grass species on Trinity gest a useful combination of the parental crosses (R.D. Burdon, pers. comm.). Dam—an earthfi ll structure in northern species has been captured in this particular e initial success of the knobcone California—showed the knobcone × cross: with the desirable growth character- × Monterey crosses prompted further Monterey hybrid to be one of the most istics of Monterey pine and the environ- investigation and hybrid seedlings were promising revegetation choices. Numer- mental hardiness of knobcone pine. Some outplanted. Specimens of each parental ous seedlings of this cross were planted second-generation seeds from these crosses species and hybrids from controlled on the site in the mid-s in a fi eld (i.e., progeny from interspecifi c trees) are crosses growing at e Eddy Arbore- test that also investigated the eff ects of being held by CDF in controlled storage tum (USDA Forest Service, Placerville, added fertilizer and the use of bareroot conditions. Although the production of California) and the nearby Camino versus containerized material (W seedlings from this cross by CDF has been Arboretum were studied in the late s and M ). Depending on halted because of the pitch canker epi- to determine parental contributions to which seed source was used, interspecifi c demic, there continues to be some interest the morphological and physiological hybrids between Monterey and knobcone from areas outside California. (L.A. Lip- status of the hybrids. With few excep- pines may also show improved resistance pitt, pers. comm.).
56 pitch canker, caused by the introduced fungus Fusarium is no evidence of this to date for pathogen strains resident circinatum, was fi rst discovered in California in , aff ect- in California (e.g., G et al. ). However, exotic ing thousands of trees in the summer of throughout strains (from Mexico and Florida) have been found that are Santa Cruz County, California (MC et al. ). At that more virulent than resident strains, based on growth cham- time, one strategy proposed was “to do nothing because it is ber innoculations. Such strains could compromise genetic thought that the fungus will not kill trees and infected trees resistance in some Monterey pine genotypes (T.R. Gordon, will recover” (T and MC ). e pathogen pers. comm.). then spread to Monterey pine populations at Año Nuevo Numerous laboratory, nursery, and fi eld trials are in and Monterey. Infestation in the Cambria population was progress and planned which should elucidate genetic rela- discovered in (A et al. ). Twelve other pine tionships. erefore, it is not yet apparent what may be the species (eight of them native to California) and a Monterey most appropriate breeding and delivery systems—if any are × knobcone hybrid were quickly tested in greenhouse studies to be recommended—for pitch canker resistance. Further- and found susceptible to the pitch canker fungus (MC more, as there may be diff erences between juvenile and ma- et al. ). ture resistance, studies need to be long term in nature before In California, the disease is often described as a ‘pest defi nitive information can direct management. Although complex’: native insects such as twig and bark beetles act as development of selection and breeding programs in parallel vectors of the fungus, and fungal infections may weaken the with genetic research on pitch canker is a responsible strat- tree and provide new habitats for the beetles. ough the ex- egy, actual deployment of any plants from such programs act relationships between the insects and the fungus are yet would not be advised until the genetic basis for resistance to be elucidated, the overall eff ect may be greater than the is understood and the need for such assisted regeneration is combined eff ects of the individual insects or fungus alone well reasoned and well informed. (O ). Given the high degree of mortality, and the For activities that are directed towards some specifi c goal evidence of some genetic basis for resistance, there may be a (such as selecting trees that lack symptoms of pitch canker major genetic impact on the species from this epidemic. e in the hope of fi nding pitch-canker resistance), there is an degree and nature of genetic impact will depend on overall attendant loss in genetic diversity of the collection (because amount of mortality, the genetic basis for resistance or toler- sampling is narrow). Unnecessary losses of genetic diver- ance (and hence selection eff ects), and the age at which most sity in the sample can be minimized by keeping the genetic trees are aff ected. If, for example, much of the mortality is base as broad as possible (e.g., sampling from as broad an among older trees, they would have already made, or had area as possible within the local adaptation zone, sampling the opportunity to make, contributions to younger genera- from trees distant from one another, sampling from cones tions. However, because a healthy Monterey pine tree is of diff erent ages and locations in tree crown thereby perhaps reproductively active for decades, any curtailment in that re- sampling from diff erent years of pollination or seed produc- productive period could have an eff ect on its overall genetic tion). For such management-directed activities, natural—as contribution. opposed to human-determined—selection should be used Introduced disease issues stimulate debate and research and accommodated as much as possible, allowing as much concerning the most appropriate, if any, management re- of the selection of seedlings as possible to happen in the for- sponse. At the time of publication of this report, the nature est rather than the nursery. and genetic basis of resistance to pitch canker were not well Finally, there is good reason to be cautious in any man- understood. Results of controlled studies may vary accord- agement approach towards manipulating genetic diversity ing to the source of genetic material for the pines, the type for resistance to an introduced agent. Artifi cial selection for of fungal isolates used, the infection protocol, and how resistance is generally only a short-term strategy that is not resistance is measured. One greenhouse study found little appropriate for long-lived species such as Monterey pine. resistance to pitch canker among samples from the native Resistance can break down in annual plants, so it is not rea- mainland and Cedros Island populations. As a species, Mon- sonable to expect that it would be durable in a long-lived terey pine was one of the least resistant among the pine species. e considerable history of experience in agricul- species studied for resistance to pitch canker (H and ture suggests there are relatively few cases where individual D ). InIn other studies, vvariabilityariability in susceptibility host plant resistance genes have maintained their effi cacy for among individual trees of Monterey pine suggests there may more than a few decades. In fact, the salient feature from be some genetic basis (e.g., S et al. ). e diver-diver- the agricultural experience is the ability of the pathogen sity within the fungus (measured in one system as vegeta- populations to evolve rapidly and adapt to genetic or chemi- tive compatibility groups, VCGs, e.g., W and G cal control measures (MD and MD ). ), coupled with evidence for recombination between However, most of the agriculture examples are based on ma- VCGs of the fungus in the laboratory (W et al. ), jor gene resistance, and while the basis of any pitch canker suggest that there is the potential for a dynamic relationship resistance in Monterey pine is not known, early results sug- between host and pathogen. Furthermore, there is the pos- gest that it is a quantitatively inherited trait. If this proves to sibility that diff erent genotypes of Monterey pine may have be the case, prospects for durability are likely to be greater diff erent susceptibilities to infection by diff erent strains of (T.R. Gordon, pers. comm.). A crucial factor is that disease the pathogen (K.R. Wikler, pers. comm.), although there resistance is almost always just one of many components of 57 fi tness, and any selection for resistance is likely to incur a fi ciently common to have been noticed and identifi ed (Table cost in the selection diff erential for other fi tness components ). is list is probably not comprehensive. Following (B a). R et al. (), a species in Table was consid- Given the long-lived nature of Monterey pine and the ered invasive if it is not only surviving and regularly repro- uncertainty of how any resistance may play out over the life- ducing, but doing so some distance from the original site of time of an individual tree, the potential for complex interac- introduction. Furthermore, the term invasive has been used tions between the pines and new variants of an introduced here without any inference to environmental or economic pathogen, and the potential to inadvertently screen out valu- impact. Approximately two-thirds of the species identifi ed able genetic diversity, a cautious and conservative approach were also considered invasive in at least one of the three na- to any genetic manipulation motivated by introduced biotic tive pine populations. Five species were considered invasive infl uences is indicated. in all three pine populations. Because this table represents e prospect and reality of introduced biotic infl uences the summary of several respondents for each population— reinforces the need for maintaining genetic diversity in na- each of whom commented on the area of the forest with tive populations of Monterey pine. A large palette of genetic which they were familiar, a species was designated as inva- diversity, expressed in good levels of regeneration, will allow sive for a pine population if one or more of the respondents scope for strong natural selection to operate in a biotic crisis identifi ed it as such. (R.D. Burdon, pers. comm.). Recommendation : e naturenature and extent of exoticexotic invasiveinvasive Recommendation : AnyAny breedingbreeding and delivdeliveryery prprogramogram plants in the range of Monterey pine forests should be deter- aimed at providing disease-resistant trees for use within the mined and an eff ective approach devised towards the control or genetic sphere of infl uence for native Monterey pine populations elimination of those exotic species considered harmful. should be well informed about the genetic basis of resistance for that disease, the inheritance of the desired trait, its interaction Finally, animals have been introduced to all fi ve Mon- with the environment, and the overall impact of artifi cially se- terey pine populations as livestock or pets that have become lected genotypes on the genetic diversity and population viability feral. e impact of introduced animals is most extreme on of Monterey pine and should not unnecessarily screen out poten- the pines on Guadalupe Island. is infl uence will be dis- tially valuable genetic diversity. cussed separately in the following section. Other common, introduced biotic infl uences in native e Mexican island populations populations of Monterey pine are an array of exotic plant Because of the special conditions of islands in general, species. Exotic invasive plants can aff ect native ecosystems in and because of the extreme current and potential impacts numerous ways: directly displacing native species; changing from exotic invasive species, the Guadalupe Island and Ce- drainage systems, microclimate, nutrient cycling, or light dros Island populations of Monterey pine are of special con- levels; and aff ecting pollinators and other interdependent cern and may require diff erent or additional conservation ac- species. M () lists over plant species that have tivities relative to the mainland populations. In addition to been introduced to Guadalupe Island over the last two cen- exotic invasive plant species, cats, dogs, rats, and goats have turies, and another that are probably introduced. Among been introduced to both islands (MC and T the former list are tocalote or Malta starthistle (Centaurea ). Various possibilities for providing fi nancial, profes- melitensis), California bur cloverclover (Medicago polymorpha), and sional, and genetic support exist, including involvement by tree tobacco (Nicotiana glauca)—all also introduced species concerned scientists in Mexico, Australia, and USA; the pos- to California. sibility of reintroducing some lost genetic diversity through In California, it has been estimated that invasive plants use of seeds from earlier collections; and the possibility of cost the State hundreds of millions of dollars annually doing some artifi cial regeneration if and when the situation (CEPPC ). Although no comprehensive studies have (goat removal or control or soil erosion considerations) is been reported on their impacts specifi cally on Monterey conducive to seedling survival (Box ). e proper sequence pine forests, there is considerable evidence of exotic plant and duration of these various activities are such that in situ species in these forests. For example, pampas grass (Corta- genetic conservation and restoration activities require long- deria selloana) is designated as one of the most invasive wild- term commitment, appropriate coordination, and agree- land pest plants in California, with Monterey pine forests ment by both those aff ected (e.g., fi shing communities on one of the several habitats of concern (CEPPC ). the island) and those responsible for administering manage- Invasive plants can exert genetic eff ects on Monterey ment policies. To the extent that international involvement pine if, for example, they directly aff ect regeneration events could provide support to the Mexican government for fur- such as seedling germination, establishment, or recruit- ther protecting the Monterey pines and associated biota on ment. ey could also indirectly aff ect natural selection if Guadalupe and Cedros Islands, there is considerable interest they change microclimate or availability of soil moisture or in doing so. nutrients. A recent, informal survey (via questionnaire) of exotic, Recommendation : e internationalinternational concernconcern and inter- invasive plant species in native Monterey pine forests in est for the Guadalupe Island and Cedros Island populations California indicated that approximately species are suf- of Monterey pine should be used by Mexican authorities and 58 scientists to provide support Table . Exotic plant species occurring in native Monterey pine forests in California. for conservation policies and practices. Species Presence† ere is particular con- Scientifi c name Common name Año Nuevo Monterey Cambria cern for the Monterey pine Acacia baileyana Bailey acacia — P — population on Guadalupe A. melonoxylon Blackwood acacia — I P Island. Here, there are in the order of adult trees A. longifolia Sydney golden wattle — P — remaining, down from ap- Ammophila arenaria European beach grass I — — proximately reported Arctotheca calendula Capeweed I I — years ago (B ), and no eff ective natural re- Arundo donax Arundo, giant reed — — P generation. When a popula- Avena fatua Wild oat I I — tion is quickly reduced to a Briza maxima Rattlesnake grass I I I small fraction of its original B. minor Small quaking grass P P I census number, conven- tional wisdom suggests that Bromus diandrus Ripgut brome P I — random genetic drift will Carduus pycnocephalus Italian thistle I I I induce a massive loss of ge- Carpobrotus edulis Iceplant I I P netic variability which will be confounded through a Centaurea solstitialis Yellow star thistle I — P subsequent increase in in- Cirsium vulgare Bull thistle I P P breeding and fi xation of Conicosia pugioniformis False iceplant — P — mildly deleterious alleles, Conium maculatum Poison hemlock I I — thereby reducing evolution- ary potential and increasing Cortaderia selloana Pampas grass I I I the probability of population C. jubata Jubata I I I extinction (e.g., F Cynodon dactylon Bermuda grass — I — and S ; L et al. ). us, the loss of Cynosurus echinatus Dogtail grass I — P trees on Guadalupe Island Delairia odorata Cape ivy, German ivy I I I could push this population (= Senecio mikanoides) through a bottleneck. How- Erechtites glomerata Australian fi reweed I I — ever, both empirical data E. mimima Australian fi reweed I P — and theoretical observations suggest that the genetic con- Ehrharta erecta Veldt grass — I — sequences are neither certain Festuca arundinacea Tall fescue — P P nor simple. N et al. (), Genista monspessulana French broom I I I using theoretical models, found that genetic eff ects Hedera helix English ivy P I P are expected to depend on Holcus lanatus Velvet grass — P — both the size of the bottle- Hypericum canariense Canary Island hypericum I — — neck and how quickly the Lolium perenne population expands subse- Perennial ryegrass P I — quently. Reviewing several Oxalis per-capræ Bermuda buttercup P P I empirical studies, C Pennisetum clandestinum Kikuyu grass — I I () fi nds that the genetic P. setaceum Crimson fountain grass — — P eff ects of bottlenecks depend on how long the population Phalaris aquatica Harding grass P — P stays at the depressed census Polypogon spp. Rabbit foot grass P — P and whether the bottleneck Tetragonia tetragonioides New Zealand spinach P P — is a single event or repeated. us, a single bottleneck Ulex europæus Gorse I I — event after which the popu- Vinca major Periwinkle I I P lation quickly expands in †P=present, meaning that the species has been positively identifi ed within a particular Monterey pine number is the least harmful. population. I=invasive, meaning that the species is not only present but has been identifi ed as spreading e more recent the bottle- some distance from its original site of introduction.
59 neck, the greater the probability that the deleterious eff ects Cumulative eff ects of a bottleneck can be avoided or minimized by mitigative Finally, it is important to recognize that eff ects on for- management procedures, such as habitat enhancement or est ecosystems act cumulatively and interactively. Habitat introduction of immigrants (i.e., supplemental genetic varia- loss, fragmentation, and climate change collectively set the tion from ex situ reserves) (L et al. ). Further- stage for major impacts on the ability of species to disperse more, a bottleneck event may aff ect various kinds of genetic and adapt and may lead to increased rates of extinction over variation diff erently: although allozyme variation typically those previously seen. For example, forest fragmentation has declines following a bottleneck, there may be an increase in been shown to markedly aff ect the climate experienced by genetic variance for quantitative traits. Dangerous genet- those fragments relative to a continuous forest (e.g., S- ic eff ects might be expected after a repeated succession of et al. ). Loss of forest habitat can contribute to bottlenecks during which the population does not increase climate change, which can further contribute to species de- appreciably. is situation would be expected to erode not cline, and so on. For example, the Intergovernmental Panel only allelic but quantitative variation. e genetically depau- on Climate Change estimates that tropical deforestation was perate populations of the northern elephant seal (Mirounga responsible for to of global, anthropogenic green- angustirostris) and the cheetah (AcinonyxAcinonyx jubatus) appear to house gas emissions during the s (B et al. ). be cases in point (C ). Of the fi ve populations, Guadalupe Island excites the Outreach needs most suspicion of a bottleneck due to its current low cen- sus. Based on the levels of allozyme variation, M et al. Given the diverse array of conditions that Monterey pine () suggested that the small population size on Guadal- inhabits through its fi ve native populations, it is truly a con- upe Island is relatively recent (in evolutionary time scales) servation challenge. Eff ective and appropriate genetic man- and does not refl ect repeated bottlenecks. A test to detect agement of Monterey pine requires a breadth of information recent bottlenecks from allele frequency data (C and experience. Supportive science for this endeavor— and L ) was used by the author with the same though substantial—is far from complete, and application of allozyme data tested by Moran et al. e test showed no science to management is complicated. erefore, it is dif- evidence of recent reduction in eff ective population size. fi cult to develop expertise in all aspects of genetic conserva- However, these results are based on seeds collected in , tion of Monterey pine. Ongoing discussions and education when the census size was almost twice what it is today. In are critical conservation tools. A recent initiative through the any event, a total population size of trees, most of them University of California, framed as the ‘Monterey Pine For- reproductively isolated or in small groups, is cause for con- est Ecology Cooperative’, is intended to improve the use of cern. It is important to apply to Guadalupe Island lessons scientifi c information in Monterey pine forest conservation, gained from empirical and theoretical studies concerning encourage more research on these forests, and provide a sup- bottlenecks. Specifi cally, it is important that the population portive network for science-bawsed conservation activities expand quickly and soon, and that the possibility is consid- (Box ). ered of reintroducing some genetic diversity from ex situ col- lections (Box ). e latter restoration tool, however, should only be used if Box . Ex situ conservationconservation rreserveeserve of the GGuadalupeuadalupe IIslandsland genetic research on seeds collected in shows that considerable genetic population of Pinus radiata. diversity has been lost in the last two “A EX in . So the population is defi nite- decades or if there are high levels of situ conservation planting was made in ly on the way to extinction—there is no inbreeding. However, even if restora- Australia in to conserve the Guada- regeneration, due to the grazing pressure tion activities are not justifi ed by ge- lupe Island population of Pinus radiata of numerous goats. netic criteria, there could be a need for which is threatened with extinction. e “It is planned that seeds for the next intervention if natural regeneration is Southern Tree Breeding Association Inc. generation will be collected in the centre not successful for other reasons, such (STBA) planted ha of Guadalupe of the block when the adjacent routine as soil erosion. seedlings, at . × . m spacing, near plantation of radiata pine is felled and Tantanoola, north of Mount Gambier, regenerated at about age years. ere Recommendation : e GuadalupeGuadalupe in the state of South Australia. e seed will be a ‘window of opportunity’ for a Island population of Monterey pine came from families collected on few years when unwanted pollen from requires immediate attention including Guadalupe in and families col- routine plantations is at a minimum. removal or control of the goats, an assess- lected in . Basilio Bermejo found e Tantanoola planting is intended as a ment of the impacts of the introduced fl o- only about native trees alive on Gua- long-term replacement for the native for- dalupe Island when he collected there est on Guadalupe Island. ra and development of a plan to manage in with CAMCORE. Bill Libby “ e ex situ reserves in South Australia these eff ects, and a genetic assessment of and I (and several other enthusiasts for may be a source of seed for restoring the remaining pines to determine if direct conservation of forest genetic resources) Guadalupe Island pine should the dire restoration activities are required. counted [approximately ] in prediction of extinction be fulfi lled.” (L ). L et al. () counted ( Eldridge ).
60 Recommendation : AnAn educational forumforum on MMontereyonterey pine rather than clonal material, and by planting a larger num- should be organized that provides ongoing opportunities for ber of trees each with some survival risk rather than trying exchange of ideas, presentation of scientifi c information, and to install a few trees with perhaps lower individual survival discussion of applications among managers, scientists, and con- risk but with less genetic diversity. is would allow more servationists. opportunity for natural selection, maintenance of genetic- environmental relationships, and maintenance of genetic Public attitudes almost certainly infl uence the suite of diversity. options for conservation-related management of Monterey is issue is very much related to earlier discussions on pine. Genetic literacy among the general public, including genetic contamination and on mitigation and other plant- its relevance to conservation and management of Monterey ings of Monterey pine. Similarly, standards and practices pine, is probably low. ere is lack of understanding of the will vary depending on context—such as whether the activ- long-term consequences of using a small genetic base (which ity is within the genetic sphere of infl uence for native Mon- is superfi cially appealing because of uniformity) for plant- terey pine forests. ing purposes. is lack of understanding may reduce forest managers’ opportunities to practice genetically appropri- Recommendation : PublicPublic outreach,outreach, parparticularlyticularly on the im- ate activities. For example, one possible manifestation of portance of maintaining local adaptations in native Monterey genetic illiteracy could be public intolerance of diversity pine forests, is critical to enabling an appropriate suite of op- in planting stock or intolerance to accepting some survival tions for genetic conservation of Monterey pine and should be risk (e.g., in the seedlings) by using an array of individuals aggressively pursued. rather than clones. Although it may be appealing to plant clonal Monterey pines that have some particular feature, do- ing so may—if planted in many copies over a broad area for Research a long period of time—contribute to lower genetic diver- Much basic research, and primarily ecological and geneco- sity in natural Monterey pine forests because of the lower logical research, remains to be done for the native Monterey genetic diversity in the pollen and seeds of these clonal trees. pine forests. It is important to recognize the continuum ere is considerable evidence for inbreeding depression in between genetic diversity and other species attributes in dis- Monterey pine. e public could assist in good genetic con- cussing the critical research needs. For example, the dynamic servation strategies by using locally adapted Monterey pine nature of Monterey pine has been emphasized throughout planting stock (rather than trees from a diff erent geographic this report—its evolutionary history of movement and re- area or an unknown geographic source), by using seedlings sponse to climatic triggers, and its current situation which seems to demand adaptation in place. Box . e Monterey Pine Forest Ecology Cooperative. erefore, studies that explore the spe- cies’ ecophysiology, ability to colo- C - agencies, private companies with large nize environments at the margin of vation-directed management of forests is forest holdings, nongovernmental orga- its current range, and enhance stress best assured of long-term success if based nizations, universities with faculty who tolerance may be very important. For on science. However, science does not are actively doing research on Monterey example, it has been demonstrated for make its way from refereed journals to pine forest ecology and genetics, and some pine species that mycorrhizæ can conservation practice without consider- other research or conservation organiza- enhance nutrient uptake, resistance to able selection, interpretation, and appli- tions as appropriate. e Cooperative toxicity, and resistance to fungal patho- cation. In fact, deciding what scientifi c received generous fi nancial support from gens (R ). information is most relevant, and how to e David and Lucile Packard Founda- interpret and apply this information, is tion for its fi rst year of activity. In addition to some critical re- a critical but weak link in the process of During the inaugural year, Coopera- search needs, there are also some ap- science-based forest management. tive activities included fi ve meetings for plied studies—surveys or reviews—that e Monterey Pine Forest Ecology scientifi c presentations and fi eld tours, a would support genetic conservation Cooperative was organized in workshop on control and prevention of goals or forest conservation in general. by the University of California (UC) exotic invasive plant species in Monterey Because of diff erences in site history, (Deborah Rogers, Genetic Resources pine forests, a seminar on Monterey pine ecological or genetic attributes, or en- Conservation Program) to act as a po- as a plantation species in Australia, the vironment among the fi ve Monterey litically neutral, science-based, support awarding of four research grants for stud- pine populations, some of the recom- group for Monterey pine forests to assist ies on Monterey pine forests, and many mended research or surveys are popula- in providing scientifi c information for contributions to articles, decisions, and conservation planning, conservation management plans related to Monterey tion specifi c. e topics are not listed management, research, and educational pine. More information about the objec- in order of priority. eff orts for native Monterey pine forests. tives and activities of the Cooperative is organization is a cross-boundary can be found at its website (URL http: Recommendation : Research,Research, sursurveys,veys, entity, with members from the Monterey //www.grcp.ucdavis.edu/projects/ or reviews that should be undertaken for pine land-holding government agencies MPFECdex.htm). Monterey pine are: and land trusts, policy-administering
61 • A comprehensive vegetation survey of native Monterey • Investigation of the viability of seeds in situ over their pine forests, including associated plant species and ex- temporal and spatial range, including persistence and tending to the geographic limits of the species. viability in the ‘canopy seedbank’ over time and the • Mycorrhizal studies that will illuminate the relation- eff ects on seed viability of site conditions and microcli- ship between forest ecosystem health and mycorrhizal mate. dynamics, and the specifi city of this relationship—if • Determination of optimum species-specifi c seed storage any—among the fi ve populations. conditions that maintain viability and genetic integrity for long-term conservation. • Soil/vegetation/ecological surveys for all populations, acknowledging that much of this has been done for the • Research on the amount of genetic diversity in the Gua- ecological staircase area of the Monterey population. dalupe Island population, losses of genetic diversity since goat introduction, and current level of inbreeding. • Examination of relationship between microclimate or ‘distance from ocean’ eff ect and genetic diversity within • Research on the relationship between fi re and function the Monterey population. of the Monterey pine forest ecosystem, including the eff ects of fi re on nutrient cycling, litter removal, soil • Determination of whether the ‘outliers’ near the Año sterilization, seed release and germination, seedling re- Nuevo population are planted or naturally occurring. cruitment, age structure, and genetic composition. • Investigation of genetic diff erences between the main • Identifi cation of an array of private or semi-private Cambria population and the Pico Creek stand. DNA marker alleles for the three mainland populations • Investigation of phenological diff erences within and to enable identifi cation and quantifi cation of genetic between Monterey pine populations in situ. contamination. • Determination of the eff ects on genetic diversity and • Research on population dynamics including the role of structure from various enhanced or artifi cial regenera- adaptation in genetic structure, the genetic interactions tion techniques (e.g., mechanical creation of gaps). of extant populations, and dispersal rates and effi cacy.
62 References
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Potential for outcrossing in an pitch canker on Monterey pine with fungisol injection. apparently asexual population of Fusarium circinatum, J Arboric :–. the causal agent of pitch canker disease. Mycologia : T, S., P. B, M. T, P. H, and L. –. T. . A strategy for conserving, manag- W, M.D. . Inbreeding depression and genetic vari- ing and better utilizing the genetic resources of Dac- ances estimated from self- and cross-pollinated families rydium nausoriense (Highlands(Highlands YYaka).aka). SPRIG PProject/roject/ of Pinus radiata. Silvæ Genet :–. Department of Forestry. Suva, Republic of Fiji. W, M.D. and J.T M. . Pinus nigra prov- T, J., C. P-L, T. S, and A.S. enance variation and selection in New Zealand. Silvæ O (eds.) . Conservation of forest genetic Genet :–. resources in Europe. Proceedings of the European Forest W, B.C. . Gene-pool reserves of Douglas fi r.For Genetic Resources Workshop, November , So- Ecol Manage :–. pron, Hungary. International Plant Genetic Resources W, D.S. and G.A.E. G. . Genetics and con- Institute. Rome, Italy. servation. Agric Ecosyst Environ :–. T, P.M. and L.P. B. . OverwinteringOverwintering ecology W, R. and W. H. . e importance of of the monarch butterfl y,Danaus plexippus L., in Cali- using ‘local’ plant genetic resources for rehabilitation in fornia. Ecol Entomol :–. California State Parks. Cal Ranger Summer –. V, C. . Provenance variation in Pinus radiata at W, S. . Evolution in Mendelian populations. Ge- two sites in northern Greece. NZ J For Sci :–. netics :–. V, M. . Conifers: Morphology and variation. W, S. . Evolution and the genetics of populations, Grafi ćki Zavod Hrvatske. Zagreb, Croatia. Volume . University of Chicago Press. Chicago, IL USA. V, R.J. . e ecology of the knobcone pine in the W, H.X., A.C. M, and D. S. .. IInbreed-nbreed- Santa Ana Mountains, California. Ecol Monogr :–. ing in Pinus radiata. II: Time course of inbreeding depres- W, G.A. and G. M. . Container hybrid sion and eff ect on growth curve.NZ J For Sci :–. pines survive on a harsh dam site. Tree Planters’ Notes : W, J., K.V. K, and S.H. S. . Abun- –. dant mitochondrial genome diversity, population diff er- W, S.B., P.M. R, D.D. M, W.H. C, entiation and evolution in pines. Genetics :–. and P.R. E. . Forest canopy structure at over- W, J., KV. K, and S.H. S. . Nuclear wintering Monarch butterfl y sites: Measurements with DNA diversity, population diff erentiation, and phylo- hemispherical photography. Conserv Biol :–. genetic relationships in the California closed-cone pines W, P.V. . Vegetation in relation to geological sub- based on RAPD and allozyme markers. Genome : stratum and fi re in the San Luis Obispo quadrangle.Ecol –. Monogr :–. Y, R.C. and F.C. Y. . Multilocus structure in W, N.C. and R.P.R.P. G. . Population struc- Pinus contorta Dougl. eor Appl Genet :–.
73 74 Appendix A
Participants: Monterey pine genetic conservation workshop
Workshop held April –, in Big Sur, California.
Michael G. Barbour Joanne H. Kerbavaz Department of Environmental Horticulture California Department of Parks and Recreation University of California San Francisco, CA Davis, CA Jay H. Kitzmiller David T. Bates Genetic Resource Center Big Sur Land Trust USDA Forest Service Carmel, CA Chico, CA Paul D. Cylinder Mary Ann Matthews Jones & Stokes Associates, Inc. California Native Plant Society Sacramento, CA Monterey Bay Chapter Ann Dennis Monterey, CA California Native Plant Society Patrick E. McGuire Berkeley, CA Genetic Resources Conservation Program Paul A. Dubsky University of California Pebble Beach Company Davis, CA Pebble Beach, CA Leonard P. Nunney Susan J. Frankel Department of Biology State and Private Forestry University of California USDA Forest Service Riverside, CA Vallejo, CA Constance I. Millar Richard H. Hawley Pacifi c Southwest Research Station Greenspace— e Cambria Land Trust USDA Forest Service Cambria, CA Albany, CA Kimberly A. Hayes California Native Plant Society Sandra C. Morey Santa Cruz County Chapter California Department of Fish and Game Santa Cruz, CA Sacramento, CA Deborah S. Hillyard Nicole E. Nedeff California Department of Fish and Game Big Sur Land Trust Morro Bay, CA Carmel, CA 75 Donald R. Owen Scott L. Stephens California Department of Forestry Department of Environmental Science, and Fire Protection Policy and Management Redding, CA University of California Berkeley, CA Deborah L. Rogers J. Jesús Vargas-Hernández Genetic Resources Conservation Program Instituto de Recursos Naturales University of California Colegio de Postgraduados Davis, CA Montecillo, Mexico
Lisa K. Schicker Detlev R. Vogler Caltrans Environmental Planning Division Institute of Forest Genetics San Luis Obispo, CA USDA Forest Service Davis, CA Stephen R. Staub B. Diane West-Bourke Del Monte Forest Foundation Rancho Del Oso Monterey, CA Santa Cruz County, CA
76 Appendix B
Respondents to the survey on ex situ reserves and international interests
Sonia Martin Albertos William S. Dvorak Jefa de la Sección de Production e Material Genético CAMCORE Dirección General de Conservación de la Naturaleza Department of Forestry Ministerio de Medio Ambiente North Carolina State University Madrid, SPAIN Raleigh, NC USA Kenneth G. Eldridge Cecilia Bester Forestry and Forest Products South African Forestry Company Ltd. CSIRO Sabie, SOUTH AFRICA Canberra, AUSTRALIA Rowland D. Burdon David R. Johnson Forest Research Institute Institute of Forest Genetics Rotorua, NEW ZEALAND USDA Forest Service Placerville, CA USA Diane L. Delany Laurie A. Lippitt Pacifi c Southwest Research Station L.A. Moran Reforestation Center USDA Forest Service California Department of Forestry and Fire Protection Albany, CA USA Davis, CA USA
77 78 Glossary
Bottleneck: a sharp reduction in the number of individuals have both parents in common (i.e., as a result of self fer- of a species or population in a particular place or time. tilization) or one parent in common (if the pollen parent Cline: a gradient of genetic variation within a population or diff ered between the two). between populations which often corresponds with an Homozygosity: at a particular genetic locus, the presence of environmental gradient such as elevation. two identical alleles; the degree to which an individual Endemic: native to a given geographic area (i.e., not exotic, has identical alleles at chromosomal loci. introduced, or naturalized). Inbreeding: mating between relatives. Inbreeding increases Extirpation: locally extinct (e.g., an extirpated population). the homozygosity in a population, and aff ects all genes. Fascicle: a close cluster or bundle of parts, such as fl owers, Inbreeding depression: loss of fi tness in a population that leaves, needles, or stems; in pines, the number of needles results from unnaturally high levels of inbreeding; more per fascicle is often a diagnostic character. commonly manifested in typically outbreeding species. Landrace: Gene fl ow: the movement of genes over space through seed a group of individuals that have become adapted or pollen movement, for example. to a specifi c area to which they were (artifi cially) intro- duced. erefore, two steps are required for develop- Genetic bottleneck: a reduction in the number of individu- ment of a landrace: introduction of some plants to a als of a species or population that is accompanied by a new area (outside of their natural range) and subsequent signifi cant loss of genetic diversity. reproduction and natural selection. e group of best- Genetic drift: random changes in genetic composition (i.e., adapted individuals that result over time is referred to as allele frequency) in populations over time; also called the landrace. random genetic drift. Genetic drift occurs more quickly Locus/Loci: the position on a chromosome occupied by a and dramatically in small populations. gene (or set of alternative alleles). Genetic integrity: the natural condition of a gene pool; free- Microsatellites: also called simple sequence repeats or SSRs, dom from genetic contamination (i.e., genes introduced lengths of DNA that consist of tandem repeats of short from nonnative or nonlocal populations). sequences of nucleotides (for example, AAT repeated Genetic load: the proportion of a population that does not times in a row). When polymorphism for the number survive or reproduce because of genetic reasons (i.e., lack of repeats is found among individuals, the microsatellite of adaptation); a measure of the deleterious portion of can serve as a genetic marker and a measure of genetic genetic diversity in a population. diversity. Genome: the total DNA of a cell’s nucleus or of a cellular Mitigation: an act that is done to soften or compensate for organelle, such as a mitochondrion or chloroplast. an act that destroys or compromises habitat or individu- Half-sib: having one, and only one, parent in common. als (generally plants and animals). us, mitigation may us, half-sibs can usually only be determined for sure involve protection of habitat in exchange for destruction when the fertilization has been controlled, so that the of other habitat, translocation of individuals, etc. parentage of the resulting seedlings is known. In nature, Panmictic: complete randomness in mating. A panmictic with open pollination, seeds coming from one tree could population is one in which every individual is equally
79 likely to mate with any other individual. reproduction from one plant. Phenotypic: referring to the observed characteristics of an Riparian: pertaining to habitats, or species occupying those individual, which may be the result of its genes, the en- habitats, that border or are associated with streams and vironment, or a combination of the two. rivers. Polymorphism: as applied to a gene, it is one that has more RAPD: acronym for random amplifi ed polymorphic DNA, than one allelic form. However, technically, the defi ni- which can be used as a genetic marker based on its dif- tion also embodies the concept of frequency. us, a ferential PCR amplifi cation from the DNA of individu- polymorphic gene, technically speaking, is a gene for als. Variation among individuals for a specifi c RAPD which the most common allele has a frequency of less marker can be a measure of genetic diversity. than . (some prefer a less stringent cutoff of .). RFLP: acronym for restriction fragment length polymor- Polymorphism is also a term used to describe the pro- phism, detected in the DNA of an individual as varia- portion of genes that are polymorphic by the above cri- tions in DNA fragment sizes that are generated by cut- terion, for an individual, population, or species. ting the individual’s DNA with special (i.e., ‘restriction’) Population: a group of individuals of the same species living enzymes. ese enzymes can cut only at specifi c DNA within a suffi ciently restricted geographical area that any sequences, so variation in the pattern of these sequences member can potentially mate with any other member. In in the genome results in fragment size variation. us, this report, the term is also used loosely to refer to each RFLP markers can be used to detect genetic diversity of the fi ve geographic occurrences of Monterey pine, among individuals. regardless of the mating relationships among the trees Serotinous: requiring fi re or extreme heat to open; com- within each location. monly used in reference to cones of certain tree species Ramet: a genetically identical copy or propagule taken from where the cones are assisted in opening (semi-serotinous) a single individual plant. is term is commonly used by fi re or require fi re or very high heat to open the scales in forestry, in relation to plants generated by vegetative and release the seeds (serotinous).
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