Rarity of mammals and its importance to listings of threatened species.

摘要

Among the rarity systems examined in this study, the seven forms of rarity model was applied to evaluate the commonness and rarity of 723 mammalian species around the world. Nearly a quarter of the species were classified into the rarest category, and another quarter of species were in the most common category; the rest of the species were in six other categories, reflecting varying degrees of rarity. This distribution of mammalian rarity displayed a strong bimodal pattern, which is different from that of plants and other animal groups. Primates, insectivores, and carnivores had the highest percentage of rarest species.; Quantitative models may provide accurate rarity analyses for mammalian species. For 170 selected species with complete quantitative data, Arita et al.'s (1990) rarity categorization, Dobson and Yu's (1993) body-size adjusted method, and Dobson and Yu's (1993) ranking method were applied and compared. Removing body size effects, according to Dobson and Yu's (1993) method, revealed some insightful information on mammalian rarity. Some seemingly abundant small-sized mammals were actually rare when body size effects were taken into account.; Tropical regions were commonly believed to have more rare species than the temperate regions. Rarity of 106 Nearctic and 108 Neotropical mammalian species was analyzed and compared. When species were classified according to Arita et al.'s (1990) scheme, without body size adjustment, the Neotropics indeed had more rare species than the Nearctic region. When body size effects were removed according to Dobson and Yu's (1993) methods, however, both regions had almost exactly the same proportion of rare species.; A case study of 119 Chinese mammalian taxa was conducted by using both the seven forms of rarity model and the 1994 IUCN criteria for categorizing threatened species. Application of the seven forms of rarity model revealed that while most species of conservation concern displayed rarity in some aspects, almost all of the species had relatively low population density. New IUCN criteria were applied to generate a new Red List for Chinese mammals. A new state protection list, which had many upgrades, was proposed based on results of this study.