RAPOPORTS RULE - TIME FOR AN EPITAPH

The christening of the decline in the geographic extent of species fro m high to low latitudes as Rapoport's rule was a bold step, Allowing f or a variety of potentially significant complications to the interpret ation of empirical studies, evidence that this is indeed a general pat tern is, at the very least, equivocal, The present taxonomically and r egionally biased set of studies lend support to the recent suggestion that the pattern is a local phenomenon being expressed primarily in th e Palaearctic and Nearctic above latitudes of 40-50 degrees N. Five hy potheses have been proposed to explain the generation of latitudinal d eclines in range size where they do occur, with the past heavy emphasi s on a climatic variability mechanism being eroded, Evidence is accrui ng 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 r esearch in ecology and evolution.