Population size, extinction, and speciation: the fission effect in Neogene Bivalvia

作者：Steven M. Stanley · 发表于：Paleobiology · 年份：1986 · DOI：10.1017/s0094837300003006 · 被引用次数：175 · 研究领域：Marine Biology and Ecology Research、Isotope Analysis in Ecology、Aquatic Invertebrate Ecology and Behavior

The extinction of a species represents reduction of both geographic range and population size to zero. Most workers have focused on geographic range as a variable strongly affecting the vulnerability of established species to extinction, but Lyellian percentages for Neogene bivalve faunas of California and Japan suggest that population size is a more important variable along continental shelves. The data employed to reach this conclusion are Lyellian percentages for latest Pliocene (∼2 ma old) bivalve faunas of California and Japan ( N = 245 species). These regions did not suffer heavy extinction during the recent Ice Age, and for each region the Lyellian percentage is 70%–71%. Discrepancies in population size appear to explain the following differences in survivorship to the Recent (Lyellian percentage) for three pairs of subgroups: (1) burrowing nonsiphonate species (42%) versus burrowing siphonate species (84%), which suffer less heavy predation; (2) burrowing nonsiphonate species of small size (73%) versus burrowing nonsiphonate species of large body size (96%); (3) Pectinacea (30%) versus other epifauna (71%), which suffer less heavy predation. During the Mesozoic Era, when predation was less effective in benthic settings, mean species duration for the Pectinacea was much greater (∼20 ma). Along the west coast of North and Central America, mean geographic range is greater for siphonate species of large body size than for siphonate species of small body size and greater s...