Conserving Threatened Rare : Some Nursery Strategies

John L. Edson 1, David L. Wenny 1, Annette Leege-Brusven 1, Richard L. Everett 2, and Douglass M. Henderson 3

Edson, John L.; Wenny, David L.; Leege-Brusven, Annette; Everett, Richard L.; Henderson, Douglass M. 1994. Conserving Threatened Rare Plants: Some Nursery Strategies . In Landis, T.D.; Dumroese, R.K., technical coordinators. Proceedings, Forest and Conservation Nursery Associations. 1994, July 11-14; Williamsburg, VA. Gen. Tech. Rep. RM-GTR-257. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 150-157. Available at: http://www.fcnanet.org/proceedings/1994/edson.pdf

Abstract—The legacy of the 1992 Earth Summit and the mandates of the Convention on Biodiversity have influenced the propagation of threatened and endangered native plants. Minimum viable population guidelines, appropriate gene pool sampling, micropropagation techniques, and strategies for returning propagules to the environment guide the development of conservation plans. The rare Pacific Northwest endemics Phlox idahonis, Douglasia idahoensis, and Hackelia venusta; oceanic island megararities; and once-abundant but now uncommon plants were evaluated for both ex situ recovery programs and other propagation opportunities. Micropropagating seed conserved scarce germplasm of rare Astragalus, Carex, and Lepidium species. The strategy of first propagating the common species, Astragalus aquilonius, was successful in culturing the closely related rare species A. amblytropis. Nurserymen can participate in species recovery programs, propagate regional rarities to promote conservation education, and prevent further decline of once-abundant native plants.

INTRODUCTION sponsored by the United Nations Conservation Committee (repre- Commission on Environment and senting seven federal agencies) and In the 1970’s, botanists became Development, in Rio de Janeiro, the Center for Plant Conservation aware that rare plant populations Brazil in 1992. The Convention, (CPC - a private consortium of were declining in many parts of the ratified in 1993 and implemented in botanic gardens) are cooperating world. Regions of high endemism 1994, requires the signatory to conserve the flora of the United particularly vulnerable to loss of nations, including the United States States (CPC 1994). diversity include remote oceanic of America, to develop National islands, areas with Mediterranean Conservation Strategies. Strategy Charles Darwin noted over 150 climates such as South Africa and goals include conducting national years ago that rarity precedes Western Australia, and parts of biological surveys to determine the extinction (Darwin 1858). While both the wet and dry tropics. life forms at risk, developing and not all rare plants are threatened, Rising concern over species’ executing appropriate in situ (on- most threatened plants are almost decline resulted in global action site) and ex situ (off-site) conserva- always rare. Hence it is natural to which produced the Convention on tion plans, and monitoring the ask whether rare species are Biodiversity at the Earth Summit, biota. The Federal Native Plant threatened. Although many factors

1 University of Idaho Forest Research Nursery, Moscow, Idaho 83844-1137. 2 Forestry Sciences Laboratory, Pacific NW Research Experiment Station, Wenatchee, Washington. 3 Department of Biological Sciences, University of Idaho, Moscow, Idaho. influence rarity (Harper 1981, recovery, and useful genetic preserve germplasm when seed Rabinowitz 1981), the greatest material (CPC 1991). After cannot be stored below freezing threats to small plant populations generating a consensus plan, team (recalcitrant seed), as is the case are human activity and random members capture the genetic with many species from the wet environmental events such as variation with seed or vegetative tropics and a few from the temper- drought, seed predation or pollina- parts, preserve the germplasm, and ate zone. Nurseries in botanic tion failure (Menges 1992). Pro- propagate plants for reintroduction gardens, arboreta, universities, and tecting habitat is the primary and or introductions to new sites. other plant research facilities necessary goal of conservation, maintain living collections for and ex situ conservation cannot For most species, a nearly research and conservation educa- substitute for habitat protection. Ex complete sample of the genome tion. situ action becomes appropriate, can be captured. CPC guidelines however, when habitat manage- recommend collecting seed from Micropropagating rare plants in ment alone cannot prevent species’ up to 5 populations per species, 50 vitro, by both seed and vegetative decline. This paper focuses on the individuals per population, and up means, is increasingly used to ex situ conservation of threatened to 20 seed per individual if that is conserve rare species. flora and describes how nursery less than 20% of the seed available Micropropagation requires only managers and plant propagators from that individual (Falk 1992, small amounts of material and can apply new strategies to con- Guerrant 1992). Vegetative propa- therefore minimizes damage to the serve rare plants. gation would require more indi- species. A useful strategy to avoid viduals to be sampled to approach wasting valuable rare material is to EX SITU CONSERVATION the genetic variation provided by develop a propagation protocol for METHODS seed. a close relative and then apply it to the threatened species. Seed is the A multidisciplinary team (includ- The primary ex situ technologies preferred choice of plant material Ing taxonomists, ecologists, geneti- involving nurseries are: storing since the sterile environment of in cists, population biologists, propa- germplasm from threatened habitat vitro seed culture can often en- gators, and habitat restorationists) in seed or gene banks, growing hance germination success over identifies the risks, assesses the living collections, and conventional propagation (Fay threats, and selects the criteria for micropropagating rare plants in 1992). When seed is unavailable, species selection. Botanic Gardens tissue culture laboratories. Seed in short supply, or cannot be Conservation International recom - banks store orthodox seed (seed germinated readily (unviable, mends working first with species which survives below freezing dormant, damaged by disease or directly threatened, followed by temperatures) of species primarily insect, etc.), vegetative species in habitat under threat of from the temperate zone and dry micropropagation techniques are disturbance, rare plants not under tropics. Viable seed dried to an appropriate (Hartmann et al. threat, wild relatives of crop plants, equilibrium moisture content of 1990). The potential explant and other categories (BGCI 1993). about 5% and stored in low (starting material) for a propagation The Center for Plant Conservation, relative humidity (15%) at -20°C trial could consist of a shoot tip, at the Missouri Botanic Garden in can potentially remain viable for up shoot segment, leaf, petiole, flower, St. Louis, lists in descending order to 200 years. or embryo. Culture involves of priority: highly endangered destroying surface microorganisms species, those rapidly declining Although requiring more space and placing the decontaminated from human causes, unique spe- and more expensive to maintain explant on a sterile gel medium cies, species with potential for than seed banks, living collections containing mineral nutrients, vita- mins, and carbohydrates. To oceanic islands, and once-abun- Pleistocene relict since it is con- increase plant numbers, plant dant but now uncommon plants) fined to northeasterly aspects on growth regulators supplement the could be considered for ex situ subalpine peaks and therefore medium to induce multiple bud plant recovery programs and other lacks upslope refugia. The species development on the explants. The propagation opportunities. We also should be carefully monitored and microshoots elongate after transfer cite examples where ex situ action taken quickly if to a hormone-free medium and, micropropagating seed and vegeta- population declines are observed. after excision from the explant, may tive parts conserves scarce root in the sterile laboratory germplasm. Hackelia venusta or showy environment or in a high-humidity stickseed (Boraginaceae), an propagation area. Finally, plantlets Pacific Northwest rarities herbaceous biennial endemic to the (micropropagated plants) are Washington Cascades (Hitchcock hardened in a greenhouse. Idaho phlox (Phlox idahonis), and Cronquist 1973), exists as one one of the state’s rarest vascular population with fewer than 500 To persist, a species must have plants, is restricted to a small individuals in habitat degraded by a minimum viable population large region of northern Idaho and is human activity. In cooperation with enough to minimize the chance of therefore considered a narrow the Forestry Sciences Laboratory extinction from random catastrophe endemic species (Moseley and at the Pacific Northwest Experi- for a long time (Menges 1992). A Crawford 1993). Recent popula-tion ment Station and the Wenatchee rule of thumb suggests a plant monitoring of Idaho phlox National Forest, we species with 5 or fewer distinct revealed eight occurrences in four micropropagated 10 clones of H. populations or less than 1,000 metapopulations, with several venusta from shoot tips. The individuals in total may become hundred to many thousand indi- explants multiplied rapidly produc- extinct if a chance event causes a viduals per occurrence, and a total ing an average of 3 new population crash (Falk 1992). of about 10,000 individuals. Since microshoots per explant per month Nursery-grown plants can be the populations appear stable and on MS medium (Murashige and reintroduced to re-establish the Potlatch Timber Corporation Skoog 1962) containing low levels species where it has declined or (which owns most of the phlox of the cytokinin benzyladanine been extirpated (Maunder 1992). habitat) plans to prevent decline of (BA) from 0.05 to 0.1 mg/l. Planting stock, however, should be this species, ex situ conservation is Microshoots of all 10 clones free of disease and pests to prevent unnecessary. rooted, at rates from 90-100%, on introduction of pathogens to the a culture medium containing the sites. Although of increasing Douglasia idahoensis was natural auxin indoleacetic acid importance in North America, described as a new Idaho endemic (IAA) at 0.5 mg/l (Fig.1). The reintroduction techniques are still species in 1981 (Henderson rooted microshoots were acclima- experimental. 1981). About as abundant as tized and grown in Rootrainer Idaho phlox, D. idahoensis containers for ease of plug extrac- APPLICATIONS numbers about 9,000 individuals tion (Fig. 2). Pest and disease-free AND DISCUSSION but is more widely distributed in 24 plantlets will be introduced at four known populations, some contain- suitable sites with initial plantings of We now examine how species ing fewer than 50 individuals 500 plantlets per site. of varying degrees of rarity (mod- (USDAFS 1993). Although these erately rare endemics of the Pacific demographics indicate no immedi- Megararities Northwest, extreme rarities on ate threat, climate warming could Human activities have pushed some result in a rapid decline of this naturally rare plants to extreme

rarity. If the genetic base of a very Figure 1. In rare plant is narrow, a species vitro rooted recovery program may not be plantlets of useful. Nurseries, however, can play Hackelia other important conservation roles. Venusta ready for acclimiza- tion. speciosa (), a woody vine species, exists as a single genotype in subtropical forest on a remote offshore island in northern (Wilson and Given 1989). Introduced goats which damaged the island vegetation have been removed but no seedling regeneration has occurred. Fortunately, cuttings taken from the wild plant have produced many plants which produce viable seed in cultivation on the mainland. Increasing popularity of this species as a garden ornamental has at least delayed its extinction, and

propagation of this megararity has developed public interest in conserving native flora of the region. It is presently unknown whether there is sufficient variation in the population of cultivated plants to allow recovery of this species, and there is a risk of contaminating the wild site with the garden fungus Phytophthora cinnamoni on reintroduced nursery plants (Maunder 1992).

Sophora toromiro, a legumi- Nous tree, was once found in

Figure 2. Fully-hardened plantlets of Hackelia venusta for introduction to a volcanic craters on Easter Island. forest site. Overcutting reduced the population

to 1 tree by 1917 which was last endemic to Western Australia. SEED MICROPROPAGATION seen by the Heyerdahl expedition Plant families widely threatened in 1955 (Christensen and Schlatzer include orchids in the wet tropics In vitro germination avoids 1993). Mature specimens were and temperate forests and bogs, dampoff and other pathogens of found growing in an arboretum on cacti in the Americas, and carnivo- conventional propagation often mainland Chile, and seedlings were rous plants in the southeastern resulting in higher survival of reintroduced by the Chilean USA. Venus Flytrap (Dionaea germinants in culture. Astragalus Forestry and Conservation Agency muscipula), a unique carnivorous columbianus (Fabaceae), once (Maunder 1992). In addition, species (Ayensu 1981) once thought to be extinct was rediscov- Jacobsen and Dohmen (1990) relatively abundant, is now threat- ered in 1976 (Sauer and have attempted to increase genetic ened by loss of habitat and trade in Mastrogiuseppe 1979). Untreated variation artificially by inducing poached plants (Culotta 1994). seed germinated at 13% on a somaclonal variation in toro miro The Convention on International propagation bench. Three weeks micropropagules. Equally important Trade in Endangered Species after scarifying with sand paper, in for the species survival, the Easter (CITES) controls export of the vitro seed germinated at 92% on Islanders are likely to protect the Flytrap, but the plant is still being MS medium supplemented with reintroductions since toro miro dug and traded within the US. The 10% agar, versus 64% germination wood was used for wood carving nursery industry could both in- of the scarified ex vitro seed (p < associated with the mythology of crease mass propagation to deter 0.001). Carex hystricina the statues (Heyerdahl 1958). digging and support government (Cyperaceae), a sedge rare in the Many other countries also propa- action to ensure sustainable use of Pacific Northwest, germinated ex gate “flagship” rarities for both this and other resources. vitro at 27% with the seed en- economic and cultural reasons. closed in the perigynium, the Idaho’s Pacific dogwood papery covering often left intact Although there are no known (Cornus nuttallii) is a disjunct of when propagating common sedge megararities in Idaho, the rarest of the widespread coastal population. species (Hurd and Shaw 1992). our plants do provide an opportu- Now infected with dogwood We compared germination rates, nity for nurseries to promote anthracnose (Discula with and without the perigynium conservation in the Interior North- destructiva), this outlier population present, both in culture and on a west. The Idaho phlox grows has produced little seed since propagation bench. Within three readily from seed in local gardens, 1990, and with fewer than 700 weeks of removing the perigynia, and D. idahoensis has grown trees remaining the population may the in vitro germination rate of 94% successfully in our Moscow be extirpated. Edson et al.(in surpassed that of the conventionally greenhouse. press) multiplied in vitro-derived sown seed by 32% (p < 0.001) shoot tips at an average rate of 2.9 (Fig. 3). Lepidium papilliferum ONCE-ABUNDANT microshoots per explant on an (Brassicaceae), an Idaho endemic, PLANTS IN DECLINE agar-based medium containing 1 germinated at 14% in vitro versus mg/l BA, and rooted 50% of the 0% ex vitro. After seed dissection, At the other end of the rarity microshoots after a basal talc dip however, 88% of the embryos spectrum are once-abundant of 4.5% IBA. Since no disease produced seedlings. endemics now in decline. Collec- resistance has been found, reintro- tion of showy natives is a major duction would likely fail. Seed VEGETATIVE problem worldwide. The interna- banking the genome and storing all MICROPROPAGATION tional trade in cut flowers threatens the clones in tissue culture are Banksia coccinea (Proteaceae) presently the only alternatives to The strategy of first propagating conserve the species. the common species, Astragalus aquilonius, was successful in Figure 3. In vitro culturing the closely related rare versus ex vitro species A. amblytropis. The two germination of Carex taxa produced an average 1.4 and hystricina with 1.8 microshoots per explant per perigynia intact or culture period (3 weeks) on MS removed. medium supplemented with 0.1 mg/ l BA, rooted at 73% and 57% on hormone-free medium, and sur- vived at 92% and 91% respec- tively. Since this protocol also produced similar results with the rare A. columbianus, some of the other more than 150 threatened species of Astragalus in the United States (Falk 1993) may also be propagated using this procedure.

Clonal variation can affect shoot growth and rooting response. The rooting of some A. columbianus endemics for a variety of uses. The aspects of rare plant conserva- clones was inhibited at moderate to positive net effect of these activities tion. H. Synge (ed.). John Wiley high levels of IAA. Minimizing the will be to promote conservation of & Sons: 19-58. concentrations of plant growth our native flora. regulators as media supplements BGCI. 1993. Workshop conclu- may lower the expression of ACKNOWLEDGEMENTS sions of the Third International differences between clones, deter Botanic Gardens Conservation callus development, and reduce the The Pacific Northwest Experi- Congress. Botanic Gardens chance of genetic change. ment Station provided research Conservation News. 2(2): 41- support for propagating the rare 48. Washington species, and the CONCLUSIONS University of Idaho Research Christensen, S.C. and Schlatzer, G. Council furnished a grant for 1993. Comments on the conser- Using efficient microprop- developing strategies for vation of Sophora toromiro agation strategies, nurseries can micropropagating rare Idaho Skottsb., from Easter Island. better face the challenges of endemics. Botanic Gardens Conservation propagating rare plants. In the News 2(2): 22-25. coming years, as the national biologic survey progresses, we will LITERATURE CITED CPC. 1994. Plant Conservation likely find increased opportunities 8(1): 4. to participate in plant recovery Ayensu, E.S. 1981. Assessment of programs to help avoid extinctions. threatened plant species in the CPC. 1991. Genetic sampling We can also propagate regional United States. In: The biological guidelines for conservation rarities and other threatened collections of endangered plants.

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