Rapoport's rule: time for an epitaph?
The christening of the decline in the geographic extent of species from high to low latitudes as Rapoport's rule was a bold step. Allowing for a variety of potentially significant complications to the interpretation of empirical studies, evidence that this is indeed a general pattern is, at the very least, equivocal. The present taxonomically and regionally biased set of studies lend support to the recent suggestion that the pattern is a local phenomenon being expressed primarily in the Palaearctic and Nearctic above latitudes of 40-50°N. Five hypotheses have been proposed to explain the generation of latitudinal declines in range size where they do occur, with the past heavy emphasis on a climatic variability mechanism being eroded. Evidence is accruing in support of more than one such mechanism. Whatever the generality of the `rule', it has undoubtedly served to stimulate a consideration of the role of spatial variation in range sizes in several areas of research in ecology and evolution.
Dept of Animal and Plant Sciences, University of Sheffield, Sheffield, UK S10 2TN.
K J
KJ
Gaston
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TM
Blackburn
J I
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Spicer