Assessment of Latitudinal Gradient in Species Richness of Sphaerotherium

Abstract

The Tropical Conservativism Hypothesis and Biogeographical Conservativism Hypothesis were tested in forest millipedes. Biogeographical Conservativism Hypothesis which suggests the processes invoked are not intrinsic to the tropics but are dependent on historical biogeography to determine the distribution of species richness. Latitudinal diversity gradient (LDG) was measured in the genus Sphaerotherium to distinguish between the two hypotheses. There was a significant correlation between the number of species and latitudinal degrees away from the equator (r=-0.8701, r²=0.7571, n=46, p<0.00001). An evolutionary preference for temperate environments appearing to have led to climatic constraints on dispersal based primarily on precipitation seasonality gradients was suggested.