Endangered Plants protect the habitat of the Haleakala silversword from invasive exotic plants (Verbascum thapsus, mullein; and Pennisetum setaceum, fountain grass) and the Argentine ant (Iridomyrmex humilis) The Argentine ant poses a significant threat to native pollinators of the silversword Competition from invasive exotic plant species may be a major contributor in the future to native plant endangerment Large, nearly pure stands of exotic purple loosestrife (Lythrum salicaria) have directly influenced the endangered small spikerush (Eleocharis parvula) in New York and Long’s bulrush (Scirpus longii) in Massachusetts Consequences of Rarity The most obvious consequence of rarity is extinction Charles Darwin, like many naturalists of his time and since, recognized that rarity often preceded extinction Small populations of sessile organisms are vulnerable to catastrophes Landslides, fire, flooding, hurricanes, and other disturbances can simply wipe out populations Small populations of vascular plants are also vulnerable to breeding problems from higher variability in breeding success caused by inbreeding Inbreeding has been documented in several localized endemics such as Limnanthes bakeri, a vernal pool species in Mendocino County, California In contrast, a common congener Limnanthes douglassii reproduces almost exclusively by cross-fertilization Stephanomeria malheurensis, a plant species confined to one small hilltop in Burns, Oregon, is auto-fertile, whereas wide-spread congeners are not Reproductive failure is not uncommon in sparse species Lower genetic variation in small populations may also make them more vulnerable to rapid environmental change Not all small populations march rapidly toward extinction Many rare plant populations can persist for centuries and millennia Sparse populations can often avoid pathogens and herbivory Pinus ponderosa, which may have been restricted to small refugia in Arizona and New Mexico at the end of the last Ice Age, has become the most widespread pine in the western United States; it now occurs from Mexico to Canada, and from California to Nebraska Other small populations may speciate (form new species) For example, two species of Ranunculus in alpine areas of the North Island of New Zealand (Ranunculus verticillata and Ranunculus insignis) have given rise to Ranunculus nivicola Legal mandates to Protect Endangered Plants Policy and Legal Mandates Throughout the World The International Plant Protection Convention held in Rome in 1951 set forth recommendations for the protection and promotion of plant life throughout the world Since then, the International Union for Conservation of Nature and Natural Resources (IUCN; now known as the World Conservation Union) has taken center stage in the protection of the world’s flora The IUCN Plant Red Book strongly defines ‘‘endangered species’’ as a species in danger of extinction and whose survival is unlikely if the causal factors (e.g., over-exploitation, extensive habitat destruction) continue operating, ‘‘including taxa whose numbers have been reduced to a critical level or 209 whose habitats have been so drastically reduced that they are deemed in immediate danger of extinction’’ (IUCN, 1998) It also identifies and tracks ‘‘vulnerable species’’ as those ‘‘believed likely to move into the endangered category in the near future if the causal factors continue operating.’’ Finally, it tracks ‘‘rare species’’F‘‘taxa with small world populations that are not presently endangered or vulnerable, but are at risk.’’ These IUCN classifications are determined by scientists and government officials around the world and classified species are not necessarily afforded legal protection after designation (Stermer, 1995) Several countries have policies or legislation that protect endangered plant species Following the Convention on International Trade in Endangered Species (CITES) of Wild Flora in 1973, 175 countries have agreed not to trade certain threatened species Many countries augment these agreements with additional legislation For example, the Mauritius National Plant Protection Legislation (the Plants Act of 1976) and the Forest and Reserves Act (1983) legally protects endangered species and habitats in the territories of Mauritius Enforcement of endangered species laws and policies in many countries is generally considered to be well-intentioned but weak The United States Endangered Species Act The intent of the U.S Endangered Species Act of 1973 (16 USC1531-1543) is to prevent further decline and help restore endangered and threatened species and the habitats on which such species depend and to ‘‘provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved’’ (Greenwalt and Gehringer, 1975) Thus, the Act recognizes the inseparable link between protecting a species, its habitat, and the surrounding ecosystem The Act also provides broad-ranging protection for all species threatened with extinction in the ‘‘foreseeable future.’’ The Act makes the ‘‘taking’’ of endangered species anywhere within the United States a federal offense, requires federal agencies to use their existing authorities to conserve listed species, prohibits federal agencies from taking actions that may jeopardize a species’ existence, provides a formal structure for listing endangered species, and provides a means for citizens to bring suit against any federal agency for failure to meet its obligations under the Act (Flather et al., 1994) Ayensu and DeFilipps (1978) noted that a species may be rare at the edge of its range, but not endangered or threatened as a whole In determining national endangered, threatened, and extinction status, the total range and abundance of the species must be considered However, states may further protect a species threatened with extirpation Still, the cost of protecting individual species and habitats against multiple stresses is high, and the reality is that enforcement on public and private lands is generally weak Selected Examples of Endangered Plants Coleus Forskohlii (Willdenow) Coleus forskohlii, a 40-cm-tall, rare herb, is found in the Yunnan Province of China, Bhutan, India, Nepal, Sri Lanka, and Africa at