The underlying drivers of β-diversity along latitudinal gradients (β-gradient) have been controversial. Previous studies have only focused on β-diversities calculated at a local scale and shed limited light on broader-scale species-distribution patterns. Here, we test the effects of broad-scale intraspecific aggregation on the β-gradient by compiling 76 regional-scale metacommunities in the New World.
We showed that the drivers of the β-gradient are scale dependent. While intraspecific aggregation contributes little to β-gradient when β-diversity was calculated at fine scales, it dominates β-gradient at the regional scale. These results resolve the debates on whether community assembly processes in general, and species-distribution patterns in particular, contribute to global patterns of β-diversity. We also found the weights that were put on relative species abundances in β-diversity measures significantly influence the β-gradient. The effect on Sørensen-type measures is stronger than on Jaccard-type measures.