Assessment of Latitudinal Gradient in Gnomeskelus Species Richness

Abstract

The Tropical Conservativism Hypothesis suggests processes of speciation, extinction, and dispersal resulted in higher species richness in the tropics and declined away from the equator. Biogeographical Conservativism Hypothesis suggests that the processes invoked are not intrinsic to the tropics but were dependent on historical biogeography to determine the distribution of species richness. 77 valid species were identified as belonging to the genus Gnomeskelus to test the two hypotheses. There was a significant correlation between the number of species and latitudinal degrees away from the equator (r=-0.7145, r²=0.5105, n=77, p<0.00001). Alternatively, there may be an evolutionary preference for temperate environments appearing to have led to climatic constraints on dispersal based primarily on temperature seasonality gradients.