Body size determines the strength of the latitudinal diversity gradient

In most groups of organisms, the species richness decreases from the tropic s to the poles. The mechanisms causing this latitudinal diversity gradient are still controversial. We present data from a comprehensive weighted meta -analysis on the strength of the latitudinal gradient in relation to body s ize. We sampled literature data on the correlation between species richness and latitude for a variety of organisms, ranging from trees to protozoa. I n addition, own data on the presence of large-scale diversity patterns for diatoms were included, both for local and regional species richness. The st rength of the latitudinal gradient was positively correlated to the size of the organisms. Strongest decreases of species richness to the poles was fo und for large organisms like trees and vertebrates, whereas meiofauna, prot ozoa and diatoms showed weak or no correlations between species richness an d latitude. These results imply that latitudinal gradients are shaped by no n-equilibrium (regional) processes and are persistent under conditions of d ispersal limitation.