Evol Ecol Res 7: 607-617 (2005)     Full PDF if your library subscribes.

Incomplete sampling of geographic ranges weakens or reverses the positive relationship between an animal species’ geographic range size and its body size

Joshua S. Madin* and S. Kathleen Lyons

National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, CA 93101, USA

Author to whom all correspondence should be addressed.
e-mail: madin@nceas.ucsb.edu


Aim: To study the effects of the sampling regime on body size/range size correlations among species.

Background: Body size/range size correlations tend to be positive if geographic sampling includes all or most of the geographic area of each species in a study. However, correlations tend to be negative or non-significant if geographic sampling is only partial.

Methods: Using computer bootstrapping, we randomly sampled latitudinal ranges of 1317 species of New World mammals. We sampled along lines of fixed longitude. We studied the effects of three variables: (1) the comprehensiveness of the sample as a proportion of the entire latitudinal range; (2) the number of isolated populations within a species range; (3) the correlation of body size and range size in the computerized data set from which the samples come. The latter is termed ‘weak’ when we used the empirical body size and range size data. It was termed ‘strong’ when we replaced the real body sizes with ones assigned to produce a correlation of one with range size.

Results: Studies using incomplete ranges yield unpredictable results that might not even get the sign of the relationship correct. The unpredictability arises because incomplete sampling tends to understate the range sizes of species with the largest ranges and miss the smallest ranges entirely. Those unusual range sizes determine the true body size/range size correlation. The unpredictability worsens as more and more locations within a range lack a population, thus increasing the probability that species will be missed by an incomplete sample. The degree of unpredictability caused by incomplete sampling and the number of isolated populations did not differ between the ‘weak’ and ‘strong’ data sets.

Keywords: body size, latitude, mammals, partial sampling, range size.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2005 Joshua S. Madin. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.