科研之友
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摘要
Some suggest that because of scale independence major biodiversity metrics can be estimated at large scales from analysis of a well chosen suite of individual sites. Others have attempted to estimate individual site patterns from analysis of the continental pool. But does such cross-scale extrapolation work? This issue is addressed for the North American terrestrial gastropod fauna by comparison of family representation, species richness and body-size patterns across site to continental scales. These data demonstrate profound differences: while the continental fauna is dominated by large body-size families such as the Polygyridae, Helminthoglyptidae, Oreohelicidae, Succineidae and Urocoptidae, average site faunas are most frequently represented by small body-sized families like the Vertiginidae, Gastrodontidae, Oxychilidae, Euconulidae, Punctidae, Valloniidae, Strobilopsidae and Ellobiidae. Species richness within sites tends to be 2-7 times smaller than random draws of individuals of the same number from regional or continental pools, indicating the potential for strong bias in the construction of site faunas. And, while the body-size spectrum for average site faunas is strongly right-skewed, the continental pool is strongly left-skewed. Thus, although taxa with biovolumes > 16 mm(3) dominate the continental fauna (79.4% of total), they make up only a small average fraction (4.1%) of individual site species lists. Within most regions, site faunas are overrepresented in species with biovolumes < 4 mm(3) and underrepresented in species with biovolumes > 128 mm(3) as compared with the regional pool. As a result, assumptions of self-similarity between observational scales in terrestrial gastropods are inappropriate.
- 出版日期2014-8
