Latitudinal richness and distribution patterns in caviomorph rodents

It has been suggested for some taxa from the northern hemisphere, that body size and geographic range width, decrease from the poles to the Ecuador, where species richness increases. In this paper, the existence of latitudinal geographic patterns of the present caviomorphs (fossorial and non-fossorial) in the American continent was tested. For each specie, data of species body length, geographic range width, species richness and mid-point of the geographic ranges, which were considered as a measure of the latitudinal distribution, were compiled. To verify if there is an effect of latitude on these variables, generalized linear models were constructed. It was observed that body size of fossorial caviomorphs and the geographic range of caviomorphs (fossorial and no fossorial) have a negative association with latitude. The latitudinal distribution of these rodents was not symmetrical with respect to Ecuador and the greatest species richness of fossorial rodents was observed between 16 degrees and 48 degrees S and non fossorial between 15 degrees N and 25 degrees S. We suggest that the observed patterns are the result of a set of complex factors, such as: geological and climatic events of the past, environmental heterogeneity, biotic interactions and continent geography.