Sheth, Seema , Lohmann, Lucia , Trish, Distler , Jimenez, Ivan .
The Wallacean shortfall: bias in estimates of geographic range size.
Geographic range size is an important variable in biogeography, ecology and conservation biology. Unfortunately, the geographic distribution of many species is poorly known (the Wallacean shortfall). Despite the widespread use of estimates of species' geographic distributions derived from natural history museum and herbarium specimens, little is known about how bias in these estimates of range size are related to geographic range size itself. Is this bias more severe for widely or narrowly distributed species? To answer this question we developed the working hypothesis that the relationship between range size, measured as area of occupancy (AOO), and bias in estimates of range size is approximately described by the central limit theorem. Three predictions follow from this hypothesis: the expected value of bias is independent of AOO, the variance of bias decreases as AOO increases, and the skewness of bias becomes less negative as AOO increases. To test these predictions we used computer simulations based on a dataset of herbarium specimen records of Bignonieae species (Bignoniaceae). The results supported all three predictions and imply that, despite a similar expected value, bias in estimates of AOO differs between narrowly and widely distributed species. For most narrowly distributed species bias in estimates of AOO was particularly high. Indeed, many of these species were not represented by any museum/herbarium specimen, and thus were unknown to science. Yet, bias was exceptionally low for a small proportion of narrowly distributed species, and the geographic distributions of these species were better known than that of any other (narrowly or widely distributed) species. In contrast, for widely distributed species bias in estimates of AOO was unlikely to be as extreme as for narrowly distributed species, so that most widely distributed species were represented by museum/herbarium specimens but their ranges were not particularly well known.
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1 - Colorado State University, Department Of Biology, Colorado State University, Fort Collins, CO, 80523-1878, USA
2 - Universidade De Sao Paulo, Insituto De Biociências, Departamento E Botânica, Rua Do Matao, 277, Sao Paulo, N/A, 05508-090, Brazil
3 - Missouri Botanical Garden, Center for Conservation and Sustainable Development, P.O. Box 299, St. Louis, MO, 63166, USA
4 - Missouri Botanical Garden, Center for Conservation and Sustainable Development, P.O. Box 299, St. Louis, MO, 63166
Presentation Type: Oral Paper:Papers for Topics
Location: Lindell A/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 8:30 AM