Ecology and Evolution of Long-Lived Semelparous Plants

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TREE vol. 6, no. 9, September 1991 Ecologyand Evolution of Long-lived SemelparousPlants One of the more dramatic life histories in the natural world is that characterized 6y a Truman P. Young and Carol K. Augspurger single, massive, fatal reproductive episode (‘semelparity’). A wealth of increasingly sophisticated theoretical models on differential life history evolution have 6een pro- duced over the last two decades. In recent species often occur in habitats related iteroparous species have gears, empirical studies of the ecology of where plants have slow growth similarly long juvenile stages6J’,12. semelpurous plants (and their iteroparous rates, such as deserts’, tropical al- Many iteroparous trees and shrubs relatives) have begun to address many pine2 and subalpines areas, bogs and most large rosette plants have aspects of the biology of these species, and to and epiphytic positions. In the sec- delayed reproduction. The long juv- test the assumptions and predictions of ond are highly branched woody enile period is perhaps more noted theoretical models. Semelparity in Iong- species with strong population- among semelparous species be- lived plants is one of the few natural level reproductive synchrony; these cause it is followed by only a single phenomena that has yielded specific quan- species occur in more mesic reproductive episode. titative tests of mathematical evolutionary habitats. An additional consequence of theory. The massive translocation of re- slow growth rates and the giant ro- sources at the time of reproduction sette growth form is the extended Semelparity is a distinct life is fundamental to the biology of time between the initiation of inflor- history in which a massive repro- semelparous species. Stored re- escence formation at the apical mer- ductive output is directly associ- sources from roots, stems and istem in the central leaf bud and ated with preprogrammed whole- leaves are moved to reproductive final seed maturation, which can be organism death. (The alternative - structures at the time of f10wering3-5. many months to years4,‘,9,‘3. This de- repeated reproduction - is known It appears that in truly semel- lay means that the environmental as iteroparity.) In plants, the syn- parous plants, virtually all avail- conditions under which flowering is drome of death after first repro- able resources are devoted to initiated are likely to be different duction can occur on several levels: reproductions5. This massive and from the conditions into which ( I I death of the reproductive mer- destructive reproductive effort seeds are dispersed, making it diffi- istem or ramet; (2) death of the makes plant death inevitable, but cult for plants effectively to track physiological individual, not in- results in reproductive outputs far year-to-year environmental vari- cluding disconnected ramets; and higher than the output per episode ation. Additionally, long-lived semel- 131 death of the entire genetic indi- of closely related iteroparous parous plants often exhibit little vidual. In this review, we restrict species or subspecies3,6,7 (Table 2). or no seed dormancy5~6,9~‘0J3-‘5, put- ourselves mainly to long-lived This parallels similar patterns in ting them further at the mercy of semelparous plant species that short-lived semelparous plants and environmental variation (but see grow for at least five to ten years, their iteroparous relatives that first Box I). and up to several decades, before flower at a similar age3. This syn- There is little understanding of reproduction and death of the en- drome of whole-organism death the genetics or the physiology of tire individual. The botanical terms associated with high reproductive semelparity in long-lived plants. monocarpy and polycarpy are effort is a special case of the more However, semelparity in long-lived equivalent to the general terms general phenomenon of the cost of plants occurs in at least 20 fam- semelparity and iteroparity, which reproduction in plants and animals. ilies (Table I), and has apparently refer to both plants and animals. Fruit and seed production in evolved many times. The existence Many short-lived plants and ani- semelparous Yucca and Lobelia are of intraspecific variation in this mals are semelparous. Among long- highly variable, and strongly related trait7J6 and interspecific hybrids be- lived organisms semelparity is to resource availability3,8. This is tween iteroparous and semelparous relatively rare, but taxonomically not surprising, given that there is species”.17 suggests that the num- diverse, including both vertebrate no alternative sink for resources. ber of mutations required to evolve (salmon, alewives) and invertebrate On the other hand, closely related semelparity is not large. (cicadas, squids) animals, and a iteroparous species may keep re- For a physiological explanation of wide variety of plant species in at productive output relatively con- semelparity, a source-sink model least 20 families. stant with increasing resource may be appropriate. In short-lived The ecological and morphological availability, but increase allocation perennial species that were nor- diversity of long-lived semelparous to vegetative structures3. Again, this mally unbranched and semel- plants can be classified into two parallels similar patterns in short- parous, experimental elimination of basic syndromes (Table 1 I. In the lived semelparous plants and their the sink (pollinator exclusion and first are unbranched rosette plants iteroparous relatives3. flower removal in lpomopsis’s) and with terminal inflorescences; these By definition, long-lived semel- supplementation of the source parous plants have extended juv- (high soil nutrient treatments in Truman Young is at the Center for Population Bi- enile stages, from a few years to Picris and Scabiosa19) resulted in ology and Dept of Botany, University of California, several decades. This ‘delayed re- branching and iteroparity. Appli- Davis, CA, USA; Carol Augspurger is at the Dept of production’ in semelparous species cation of fertilizer to normally Plant Biology University of Illinois, 505 S Goodwin has been the subject of consider- semelparous bamboo can also Av., Urbana. IL, USA. able attention4,9,‘0. However, closely result in iteroparity’O. 285 TREE vol. 6, no. 9, September 1991

Table I. Known long-lived semelparous plants Family Unbranched rosette plants with hapaxanthic shoots

Alpine Theoretical approaches to the evolution of Lobelia spp. (Africa) Lobeliaceae Trematolobelia spp. Lobeliaceae semelparity Argyroxiphium spp. Compositae Numerous theoretical treatments Espeletia floccosa Compositae of the differential evolution of Puya spp. (South America) Bromeliaceae semelparity and iteroparity have Echium wildprettii Boraginaceae Lupinus alopecuroides Leguminosae been developed over the last two decades. All assume a trade-off Subalpine between present and future re- Frasera speciosa (western US) Gentianaceae Harmsiopanax ingens Araliaceae production, i.e. that semelparity is Phoenicoseris spp. Compositae associated with an increase in Centaurodendron dracenoides Compositae fecundity (Table 2). All of these Arid and semi-arid treatments are mathematically re- Agave spp. Agavaceae lated, but they fall into three basic (Furcraea spp.) Agavaceae types of model. Yucca whipplei ssp. Agavaceae Aeonium spp. Crassulaceae Wilkesia gymnoxiphium Compositae Bet-hedging models One set of models predicts that Bogs Lobelia spp. (Hawaii) Lobeliaceae increasing environmental variability Puya dasylirioides (Central America) Bromeliaceae and unpredictability favor itero- Epiphytic parity over semelparity20,21. This for- Tillandsia spp. Bromeliaceae malizes the intuition that limiting reproduction to a single episode is Other Corypha spp. Palmae particularly risky in an unpredict- Plectocomia spp. Palmae able environment (see Box 1). How- Frasera caroliniensis (Eastern US) Gentianaceae ever, some bet-hedging analyses insufficiently known (unbranched?) rosette plants with hapaxanthic shoots’ produce the opposite prediction**. Aechmanthera spp. Acanthaceae In addition, many semelparous, Boea spp. Gesneriaceae and not iteroparous, plants are Brillentarsia nitens Acanthaceae found in habitats likely to be more Dendroseris spp. Compositae Drachophyllum verticillatum Epacridaceae variable. Annuals and biennials are Ensete spp. Musaceae typically found in habitats that Greenovia spp. Crassulaceae are ephemeral and unpredictable, Heterochaenia spp. Campanulaceae either successionally (disturbed Hymenoxys spp. Compositae Kalanchoe spp. Crassulaceae sites) or edaphically (deserts and Orchis spp. Orchidaceae dunes). Long-lived semelparous Spathelia spp. Rutaceae rosette plants are commonly found Sohnreyia excelsa Rutaceae in drought-prone habitats (Table I), Streptocarpus spp. Gesneriaceae which can be highly variable with Tauschia decipiens Umbelliferae Yunquea tenzii Compositae respect to rainfall and correlated demographic parameters3,6,9,“.17,23. Synchronously flowering branched woody plants The variability of these environ- Bamboo spp. (>17 genera, ,150 species) Gramineae Mimulopsis solmsii Acanthaceae ments is particularly difficult to track Strobilanthes spp. Acanthaceae for plants without seed dormancy Tachigalia spp. Leguminosae and with long inflorescence pre- Cerberiopsis candelabrum Apocynaceae formation times, as are common Parasite on Strobilanthes in long-lived semelparous plants. Campbellia aurantiaca Orobanchaceae aMostly from Refs 5,30 and 44. Reproductive effort model A second theoretical approach considers the relationship between present and future reproduction. In particular, Schaffer and Rosenzweig Table 2. Estimates of relative reproductive outputs of closely related long-lived semelparous and argued that selection for ever- iteroparous rosette plants increasing reproductive effort can lead to the evolution of semel- Semeloarous lterooarous Trait Ratioa Ref. parity2’. One subset of that theory Lobelia telekii L. keniensis lnflorescence dry predicts that when the curve for the weight 3-4 3 relationship between reproductive Seed set 4-5 3 Espeletia floccosa E. schultzii Total seed weight 3.6 6 effort and reproductive success is Yucca whipplei Y. w. spp. caespitosa Panicle height times convex, semelparity will be favored ssp. parishii and intermedia panicle diameter -4.0 7 (Fig. la). Therefore, they predicted aEstimates for Yucca and Espeletia are based on our calculations using published data from that when there is a positive corre- populations in close proximity. lation between reproductive effort and reproductive success per unit 286 TREE vol. 6, no. 9, September 1991

Semelparous orqenisma have a particular problem when faced w&h em&onmentat un- reproductive effort, semelparity will Semelparous syndromes predictsbility. 8eeau~~3 sem43@arous plants ‘put all their eggs in ot%e basket’, individuals be favored, but when this relation- The two distinct syndromes of that flower in years ofto%& reproductive fail- ship is absent or negative, itero- long-lived semelparous plants ure have zero Wetime f&n@=, a fete parity will be favored (Fig. 1 b). shown in Table 1 differ in many iteroparuus planta may avoid b++ fCowsring Interspecific comparisons of field aspects of their morphology and more than orme. Any cdfiort of $erne@arous plants with inv&ebk+ generation times data from three different genera ecology. It is likely that natural would run the r&k of extinction in environ- (Yucca, Agave, Lobelia) have all selection has operated in different ments with even rwe unprediteble years of shown precisely this pattern. In the ways to produce semelparity among reproductive failure. semelparous species, there were these species. Semetpgraus plaints mar to s&e this significant positive correlations be- problem in %vo d%r#tt sways. For annual plants, in whicir the time berweprn germi- tween inflorescence size and rela- Unbrancked rosette plants nation and flow&ng is Iy fixed at a tive fruit set or seed set, whereas in In some plants with terminal in- single growing seaeorx etrong seed dor- the iteroparous species, no such florescences, axillary buds are pro- mancy provides ca~tirable variation in correlation was foundl,3. Although duced at the bases of the inflor- generation time wit&& &wh CohorP. In non- annual semetparoua ptsnrs, seed dormancy this represents a remarkable co- escences, and the reproductive is weak or absent, This holds for short-lived herence of theoretical prediction shoots continue to grow after flower- (Table 3) and ~a~~~~~~~‘~‘~‘6 semal- and empirical data, so far there is no ing. In other species, there are no parous species. In these sp~ies, however, compelling evidence of a causal re- distal axillary buds, and the entire there is consider&le variatfon in post- lationship between patterns of re- shoot dies after flowering. Such germination ntaturgtion tirn~@‘~‘~, which has been eggs as ~anr~s to semel- productive success in these genera shoots are called ‘hapaxanthic’30. parous plants in ~n~~~~e environ- and their differential life history Unbranched hapaxanthic plants ment@. This varistfon could ba inherent but it evolution. Differential pollinator (architecturally, labelled ‘Holttum’s is mure likely due to m~~vi~nm~ntal preference for larger inflorescences model’ by Halle30) are semel- variation6”. Annual plants, with only mini- mal recourse to variable maturation ratas43, was initially proposed as a causal parous; branched hapaxanthic have evotved seed dormancy as an aiterna- mechanism’, but more recent ex- plants (‘Tomlinson’s model’) are tive strategy. perimental evidence indicates that iteroparous. All semelparous fn long-lived 8~~~~ spaciw p&r&u- pollinators may not limit seed set rosette plants in Table I are un- Iarty those thet ere ~~ro~~~~O, seed dor- branched and hapaxanthic. Most mancy may even be seWted again&, if or fruit set in some of these suitable establishment sites are created bv species’3,24f25, and alternative, non- have close relatives that are hap- the deaths of 8dufts*‘. adaptationist explanations are axanthic, but branched and possib1e3. In addition, some ‘semel- iteroparous4,8,‘1,‘2,‘4,‘7,30. Therefore, parous’ Agave species are clonally branch pattern is intimately related iteroparous’.4f8. Nonetheless, the to life history in this group (although theoretical basis of this model re- there are Agave deserP and Puya have no semelparous represen- mains sound, and could potentially dasyliroidesl 7 plants that both tatives30. operate not only through pollinator branch and are semelparous when Schat et al. found that several preference, but also through pred- side rosettes flower along with the traits are strongly associated with ator satiation’0p26 or pollination main rosette). semelparity in short-lived perennial efficiencylO. It appears that rosette plants plant species3’. These include the with hapaxanthic shoots are pre- rosette growth form, terminal inflor- Demograpkic models disposed to evolve semelparity. escences and large tap roots. The The third theoretical approach to Virtually all such taxa known to us fact that these traits are overrepre- the evolution of semelparity con- include at least one species that has sented also among the iteroparous siders the demographic conditions evolved semelparity. This is re- species in the same families that under which the loss of all future markable, considering the relative have many semelparous species reproductive episodes is more than rarity of semelparity among long- suggests that they predispose cer- made up for by the increase in fec- lived plants. In contrast, rosette taxa tain taxa to evolve semelparity. undity associated with semelparity. with terminal inflorescences that are An additional predisposing factor This approach has led to a series of not hapaxanthic (‘Chamberlain’s may be indeterminate inflor- increasingly complex and ‘realistic’ model’ and ‘Leeuwenberg’s model’) escences32. A large tap root and demographic models20,27-29 (Box 2). However, increasingly complex models20,27 become increasingly im- practical to test. Summarized, these Table 3. Seed dormancy of eastern US herbs differing in life history” models predict that as repeated re- Life history Dormancy none or Full dormancy b Total production becomes increasingly conditionalb species unlikely, semelparity is more likely Annuals 43 (0.49) 45 (0.51) 88 to evolve. One of these models has Polycarpic perennials 32 (0.68) 15 (0.32) 47 been used in conjunction with long- Monocarpic perennialsc 13 (0.81 j 3 (0.19) 16 term demographic data to show how the decreased likelihood of repeat “Data summarized from Ref. 45. bNumbers (and proportions) of species reproduction in drier sites can ex- “All of these are short lived. plain the evolution of semelparity in Lobelia spp. on Mount Kenya3. 287 TREE vol. 6, no. 9, September 1991

an indeterminate inflorescence pro- group is morphologically more vide energetic and structural poten- diverse, including bamboos, shrubs, tial for the large ecological and trees and herbaceous parasites. evolutionary increases in repro- Unlike most unbranched rosette ductive output associated with species, they tend to occur in mesic, semelparity. In addition, the often forested, sites. All of these combination of the rosette growth species exhibit strong reproductive form and terminal inflorescences synchrony within populations, and may combine with demographic often over the entire species range, 100% contraints to produce conditions in which infrequent reproductive that make the evolution of semel- episodes are separated by long REPRODUCTIVE EFFORT (R.E.) oaritv more likelv. Haoaxanthic periods (up to several decades) her&ems die after-the o&et of re- with virtually no reproduction. Mast- production, and rosette plants often ing by itself may not be uncom- have a limited number of active monj3, and occurs in several meristems. Rosette plants tend to semelparous rosette plants6,9-‘l. occur in habitats where growth rates However, highly synchronous repro- are slow, and many branched ro- duction exhibited by entire species sette plants therefore exhibit poly- is rarelo. annual reproduction. The mortality Janzen, in a review of bamboo of any rosette is a large loss to a reproductive ecology, suggests that plant with only a few meristems, and predator satiation favors the chance mortality associated with re- evolution of high reproductive out- production may be high. Infrequent puts on the level of both popu- reproduction and high adult mor- lations (reproductive synchrony1 tality rates may favor the evolution and individuals (semelparity)‘O. Re- of semelparity in alpine lobelias3 productive synchrony also may be (see Box I). The applicability of this enforced by increased pollination result to other semelparous rosette efficiency10,33-35. However, it is not species is not known. obvious that the factors favoring lnforescence height (R.E.) strict reproductive synchrony (seed- Branched species witk strong reproductive predator satiation, pollination ef- Fig. 1. lal Putative life history consequences of synchrony ficiency, seed dispersaP1 would alternative relationships between reproductive effort There are several long-lived also favor semelparity. For example, and reproductive success. (bl Observed relationships semelparous plant species that are one might expect that the effects of between relative reproductive success and inflorescence size in three genera of long-lived plants with woody and branched (Table I). reproductive synchrony over an en- both semelparous and iteroparous representatives While the previous group com- tire population may often swamp Redrawn from Ref 3 with permission. prised a single growth form, this the advantages of the increased fecundity of an individual plant that would be associated with semelparity. On the other hand, there may be selection for long-lived Demographic models of the differential 6, -s, = 1 (1) semelparous organisms to evolve evolution of iteroparity and semeiparity all reproductive synchrony’0,36. assume that iteroparous genotypes have less ? P=C(=l) Many of these highly synchronous fecundity per episode than semelparous woody species occur in low- genotypes, an assumption amply supported 6, -B, = PIG (2a) by field data3 (Table 2). Demographic models diversity plant communities in ask: under what demographic conditions A = C%* which they are the dominant does the increase in fecundity associated ? species, often forming nearly mono- with semelparity (&&t more than make up .A.= 1 specific stands l”J7. When synchron- for the loss of future reproductive episodes? 1 - PA (2b) ous flowering and death occur, there These models suggest that semelparity tends 4 to be favored bY decreased adult survivorship are profound effects on planP7 and animalI community structure. In (P), increased time between individual repro- Z=l X--r00 ductive episodes (Z), earlier senescence (x), 1 particular, long-lived herbivores higher population growth rates (A), and that depend on the vegetative higher juvenile survivorship (C). Only once 1 - (iYA)“z .&= (3a) structures of a long-lived semel- has any of these models (eqn 3b) been tested 4 1 - rmrz with empirical data. Young3 has shown that parous plant species are suddenly as one approaches the eco1ogical boundary deprived of their main food after its A=1 4 x--Pm between semelparous and iteroparous Lob- synchronous flowering and death. In elia species, adult survivorship and fre- at least two systems (giant pandas quency of reproduction decline, and suggests 6 1 a=- 13bI (Ailuropoda melanofeuca) and that at this ecological boundary, future repro- 4 1-F duction is so unlikely that semelparity has bamboo38J9; bongo (Boocercus eu- been favored. Reproduced from Ref. 3 with permission. ryceros) and MimulopsiS1°I this may result in herbivore population den- 288 TREE vol. 6, no. 9, September 1991

sities above local carrying capacity Semelparity is a model system of Palms, University of Chicago Press as well as increased mortality and for the development of a multi- I5 Kitajima, K. and Augspurger. C.K. f 19891 Ecology 70. I 102-I I I4 decreased reproduction. Might not disciplinary evolutionary synthesis. 16 Nobel, P.S. ( 1987) Bat. Gaz. 148, 79-84 these episodic herbivore popu- However, our understanding of the I7 Carr, C.D. (19871 Trends Eco/. Eva/. 2, lation reductions be adaptive for ecology and evolution of semel- 192-194 synchronous semelparous plants? parous plants is still rudimentary. I.9 Paige, K.N. and Whitham. T.G. ( 19871 The evolutionary origin of such an We need to know more about the Ecology68, 1691-1695 I9 Verkaar. HJ. and Schenkeveldt. A.I. adaptive behavior is not straight- phylogenetic history of the mor- (1984) New Phytol. 98,673-682 forward, however, and mechanisms phological traits associated with 20 Orzack, S.H. and Tuljapurkar, S. f 19891 akin to group selection might need semelparity, about the physiologi- Am. Nat 133,901-923 to be invoked to explain it. On the cal ecology of allocation to repro- 21 Schaffer, W.M. and Rosenzweig, M.L. ( I9771 Ecology 58, 60-72 other hand, an individual out of syn- ductive and vegetative meristems, 22 Bulmer, M.G. 11985) Am. Nat. 126,63-71 chrony would pay a large price for and most importantly, about the 23 France, A.C. and Nobel, P.S. (19901 supplying the only food available population ecology of closely re- Oecologia 82, I5 l-l 57 after the reproduction and death of lated semelparous and iteroparous 24 Acker, CL. (1982) 1. Ecol. 70, 357-372 the rest of the population, and be plants. Nonetheless, the research to 25 Sutherland, S. f I9871 Evolution 4 I, 750-759 strongly selected against. The mor- date on long-lived semelparous 26 Keeley, I.E., Keeley, S.C. and Ikeda, D.A. tality of herbivores may be merely plants has stimulated some of the (1986) Am. Mid/. Nat 115, l-9 an added benefit of this selection. most interesting theory and tests of 27 Bell, C. (1980) Am. Nat. 116.45-76 As a semelparous plant, the trop- theory in evolutionary biology. 28 Charnov. E. and Schaffer. W.M. ( 19731 Am. Nat 107, 79 l-793 ical forest tree Tachigalia vefsicolor 29 Young, T.P. (I981 1 Am. Nat. I 18. 27-36 (along with several congeners) is Acknowledgements We thank G. Fox, M. Stanton, C. Simon, A. 30 Halle, F., Oldemann, R.A.A. and anomalous’5,4’. First, it is the only Sugden, A. Herre, P. Gras, R. Karban, R. Tomlinson, P.B. ( 19781 7iopica/ Trees and highly branched canopy tree among Foster, L. Isbell, A. Smith and an anonymous Forests: An Architectural Analysis, Springer- Verlag the species in Table I. Second, its reviewer for help with the manuscript and the 31 Schat, H., Ouborg, 1. and De Wit, R. ( I9891 strong reproductive synchrony is ideas therein. T. Young was supported by a grant from the Center for Population Biology, Acta Bat. Neerl. 38, 183-20 I limited to subsets of the population University of California, Davis, CA, USA. 32 Reinartz, J.A. f 1984) 1. Ecol. 72, 9 13-925 in a given reproductive yeat”. 33 Ims, R.A. II9901 Trends &co/. Eva/. 5, Seedlings of T. versicolor exhibit 135-140 34 Taylor, A.H. and Qin, 2. ( 19881 Am. 1. Bot. unusually high survivorship and References 75, 1065-1073 physiological adjustment to varying I Schaffer, W.M. and Schaffer, V.M. 119791 35 Augspurger, C.K. I I98 I 1 Ecology 62, light conditions15. It has been Ecology 60, 1051-1069 762-774 suggested that high juvenile sur- 2 Smith, A.P. and Young, T.P. II9871 Annu. 36 Martin, A. and Simon, C. 119901 Bioscience 40, 359-367 vivorship can favor the evolution of Rev. Ecol. Syst 18, 137-158 3 Young T.P. (1990) Eva/. Eco/. 4, 157-l 71 37 Agnew, A.D.Q. 119851 1. East Afr. Nat. Hist. semelparity28, but this effect may 4 Tissue, D.T. and Nobel, P.S. f 1990) Sot. Nat/ Mus. 183, l-12 be applicable primarily to growing Ecology 7 I ) 273-28 1 38 Reid, D.G., Hu, I., Dong. S., Wang, W. and populations29. 5 Veillon. I.M. I 1971 I Adansonia I I, 625-639 Huang, Y. (1989) Biol. Conserv. 49,85-104 The selective forces that have fa- 6 Smith, A.P. f 19831 Smithson. Contrib. Bot. 39 Schaller. G., Hu jinchu, Pan Wenshi and 48, l-45 Zhu jing ( 1985) The Giant Pandas of Wolong, vored the evolution of semelparity 7 Haines, D.A. f 1941) Madrono 6, 33-45 University of Chicago Press in these reproductively synchron- II Udovic. D. f I98 I I Oecologia 48, 389-399 40 Hillman 1.C. and Gwynne. MD ( 1987) ous species are not yet clearly under- 9 Taylor, O.R. and Inouye, D.W. I 19851 Mammal/a 5 I, 53-63 stood. Empirical data are sparse, Ecology 66, 52 1-527 41 Foster, R.B. (19771 Nature 268, 624-626 and quantitative tests of hypoth- IO fanzen, D.H. (1976) Annu. Rev. Eco/. Syst. 42 Venable, D.L. and Brown, J.S ( 19881 Am. 7, 347-39 I Nat. I3 I, 360-384 eses are lacking. It is likely that dif- I I Young, T.P. I 1984) /. Ecol. 72, 637-65 I 43 Fox, G. ( 19901 Am Nat I35,829-840 ferent evolutionary pathways have I2 Augspurger, C.K. (19851 Oikos 45, 44 Carlquist, S. ( 1984) /s/and Biology, led to semelparity among the plants 341-352 Columbia University Press that comprise the two syndromes I3 Young, T.P. 11982) Ecology63, 1983-1986 45 Baskin, C.C. and Baskin, I.M. II9881 Am. 1. 14 Corner, E.I.H. (1966) The Natural History Bot. 75,286-305 described above.

Conclusion The study of long-lived semelparous organisms is one of the few c areas in which the marriage of In some countries, the currency nee&d to pay for a personal subscrip- theory and field studies has been tion {US dollars or pounds sterling) is not availat&. if you wish to help a fruitfully pursued. A picture of colleague abroed why is not abte to ben&t from ?T?EE#w this reason, we semelparity in long-lived plants will accept your payment for anotkr person’s subscripti?on. Simply that involves phylogenetic history, morphological constraints and op- complete the subscription order card bound into any issue, giving the portunity, strong ecological and recipient’s name and address i&x&led ‘send to’; after ‘signature’, give evolutionary forces, alternate evol- your own name and addresa and mark this ‘bill to’. Renewal notices will utionary pathways and a set of be sent to your address and the recipknt will receive the monthly copy of the3-..- J--.-‘-.-inumal. Plessc?.---- .inform . . -.._. the-..- .--.rriecinient .-.._ of-. vnur, --. action.- - . . - . . well-developed mathematical the- I ories is emerging from the literature.