208 



Plums — Oiiy Living Resources 



example. Nuttall's mudwort (Micninthcmiini 

 micranthemoides) has been recorded from 

 Delaware, the District of Columbia. Maryland. 

 New Jersey. New York. Pennsylvania, and 

 Virginia, but despite searches, it has not defi- 

 nitely been seen since September 1941. 



Several species of U.S. plants are extiipaled 

 from the wild, but still exist in cultivation. Most 

 familiar of these is the Franklinia {Fninklinia 

 aUikinuilui). a small tree known historically 

 only from the Altamaha River in southeastern 

 Georgia, but which is now widely cultivated as 

 an ornamental in eastern states. 



Ongoing fieldwork has resulted in the redis- 

 covery of many species. The running buffalo 

 clover (Trifoliiini stolomfenim) was rediscov- 

 ered in West Virginia in 1983 (Bartgis 1985) 

 and has been found subsequently in Indiana. 

 KenlLicky. Missouri, and Ohio. In Oregon, a 

 population of Lomatiiim pcckiamtm was located 

 in 1983 for the first time in more than 50 years. 

 The discovery of additional populations has 

 changed the species' federal status from a cate- 

 gory 1 candidate to a former candidate (Kagan 

 and Vrilakas 1993). In Montana, several recent 

 rediscoveries have occurred, including a 1985 

 rediscovery of Trifolhim niicroceplniliim. a 

 species of clover not seen since it was first col- 

 lected by Meriwether Lewis in 1805 or 1806 

 (Hoy 1993). Likewise, during the 1991 field 

 season the yellow passionflower (Passifloni 

 hitea) was located at two sites in Delaware for 

 the first time since the early 1800"s (Clancy 

 1993). These examples illustrate the importance 

 of ongoing inventories as well as the dynamic 

 nature of local and regional floras. 



Threats to Diversity 



Habitat alteration and incompatible land use 

 are the major threats to most rare U.S. plant 

 species. Apart from certain species of cacti, gin- 

 seng, and various showy wildflowers. relatively 

 few rare U.S. plants are primarily threatened by 

 overcollecting. Global climate change (Peters 

 and Lovejoy 1992; Morse et al. 1993) and sea- 

 level rise (Reid and Trexler 1991) may pose 

 addifional threats to some native U.S. plant 

 species. 



Species at higher risk of extinction usually 

 include those having small geographic ranges. 

 narrow habitat requirements, unusual life histo- 

 ries, or vulnerability to exotic pests or diseases. 

 In addition, reduced biodiversity of local floras 

 is of high concern, even if plants lost from a 

 particular geographical region are common and 

 secure elsewhere. Finally, depletion of even 

 widespread species can occur if exploitation or 

 habitat destruction occurs beyond a sustained- 

 yield rate. 



Assessment of the causes and patterns of 

 species losses in the United States, combined 

 with ongoing documentation of natural diversi- 

 ty and studies of rarity, endangerment. and 

 threats, will refine conservation priorities by 

 identifying species or areas that will most bene- 

 fit from further protection and research. 

 Analyses of ongoing inventory and monitoring 

 work could provide early warnings of wide- 

 spread threats to biological diversity, thereby 

 perhaps improving the protection of both rare 

 and more common plants and allowing the 

 development and implementation of conserva- 

 tion strategies before crises occur. 



References 



Barlgis, R.L. 1985. Rediscovery of Trifolhim swlonifcniiii 



Muht ex A. Eaton. Rliodora 87:425-429. 

 Carlquist, S. 1970. Hawaii: a natural history. Natural 



History Pres.s. Garden City, NY. 463 pp. 

 Clancy, K. 199.^. The yellow passionflower, Passifloni liileu 



L.. rediscovered in Delaware. Castanea 58:153-155. 

 Dahl, I.E. 1990. Wetlands losses in the United States 1780s 



to 1980s. U.S. Fish and Wildlife Service, Washington, 



DC. 13 pp. 

 Federal Register. 1993. Plant taxa for listing as endangered 



or threatened species: notice of review. Federal Register 



58:51144-51190. 

 Ferren. W.R., and A.E. Schuyler 1980. Intertidal vascular 



plants of river systems near Philadelphia. Proceedings of 



the Academy of Natural Sciences of Philadelphia 



132:86-120. 

 Hoy. J. 1993. Rediscovenng lost species. Kelseya [Montana 



Native Plant Society] 6:5. 

 Jenkins. R.E. 19S5, Information methods: why the Heritage 



programs work. The Nature Conservancy News 35:21- 



23." 

 Kagan. J., and S. Vrilakas. 1993. Extinct and extirpated 



plants from Oregon. Kalmiopsis [Native Plant Society of 



Oregon] 3:12-16. 

 Kartesz. J.T. 1992. Preliminary counts for native vascular 



plant species of U.S. states and Canadian provinces. 



Biodiversity Network News [The Nature Con,servancy] 



5:6. 

 Kartesz. J.T. 1994. A synonymized checklist of the vascular 



flora of the United States, Canada, and Greenland. 2nd 



ed. Timber Press. Portland. OR. 622 pp. 

 McKnight. B.N., ed. 1991. Biological pollution: the control 



and impact of invasive exotic species. Indiana Academy 



of Science. Indianapolis. 261 pp. 

 Morse, L.E., L.S. Kutner, G.D. Maddox. J.T. Kartesz, L.L. 



Honey. CM. Thurman, and S.J. Chaplin. 1993. The 



potential effects of climate change on the native vascular 



flora of North America: a preliminary climate-envelopes 



analysis. Report TR- 103330, Electric Power Research 



Institute, Palo Alto, CA. 120 pp. 

 Peters. R.L., and T.L. Lovejoy, eds. 1992. Global warming 



and biological diversity. Yale University Press, New 



Haven, cf. 386 pp. 

 Reed, RB., Jr 1988. National list of plant species that occur 



in wetlands: 1988 national summary. U.S. Fish and 



Wildlife Service, Washington, DC. 2-14 pp. 

 Reid, W.V., and M.C. Trexler. 1991. Drowning the national 



heritage: climate change and U.S. coastal biodiversity. 



Worid Resources Institute, Washington. DC. 48 pp. 

 Russell. C.A.. and L.E. Morse. 1992. Plants. Biodiversity 



Network News ]The Nature Conservancy] 5:4. 

 Smith. Clifford W. 1989. Non-native plants. Pages 60-69 in 



C.P. Stone and D.B. Stone, eds. Conservation biology in 



Hawai'i. University of Hawaii Cooperative National Park 



Resources Study Unit. Honolulu. 



