Range Size-Body Size Relationships: Evidence of Scale Dependence

The interspecific geographic range size-body size relationship for animals is widely described simply as a positive interaction. However, examples of this relationship have been reported in which geographic range size increases with increasing body size, decreases with increasing body size, or follows no simple pattern. Here we suggest that much of this variation can be explained in terms of the extent of the geographic coverage of different studies. In the main, where significant interactions are found, 'comprehensive' analyses (performed over areas which embrace a very large proportion of the geographic ranges of the species concerned) report positive range size body size relationships, whilst 'partial' analyses (performed over areas which embrace the entire geographic ranges of none or only a small proportion of the species concerned) report positive or negative relationships with about equal frequency. Some of the consequences of this observation are discussed.