Sciuridae, Rapoport’s effect and the mismatch between range size, conservation needs, and scientific productivity: an approach at the genus level

Abstract

Rapoport’s rule states that species at high latitudes have broader ranges than species at low latitudes. This rule has been strongly disputed over the years, and the majority of current scientists think that this is mostly a local phenomenon. However, if Rapoport’s rule applies, it should be a priori expected that taxa occurring in equatorial and tropical regions should be more threatened than those at temperate regions. In this paper, we test 1) whether Rapoport’s rule applies to Sciuridae genera (Mammalia, Rodentia) and, if so, 2) whether the research efforts by scientists have been concentrated on those taxa that, because of their range size, may be predicted to be more threatened (i.e. equatorial and tropical taxa). Distribution data on Sciuridae came from literature and were transformed as maps according to World Map Program, and data about number of papers published by genus and by latitude were collected from the ISI Web of Knowledge. Our analysis verified the occurrence of a Rapoport’s effect in Sciuridae in both the hemispheres: mean range size increased significantly with latitude increases in both hemispheres. However, literature data inspection revealed that only a few genera accounted for the great majority of studies, and these genera were widely distributed and found at high latitudes. Thus, there is a potentially serious gap between current knowledge and threat expectations for Sciuridae worldwide. We therefore strongly urge scientists to give priority attention towards field studies of tropical Sciuridae genera.