Latitudinal differences in species abundance distributions, rather than spatial aggregation, explain beta-diversity along latitudinal gradients

摘要

Aim Variation in species composition among sites (beta-diversity) generally decreases with increasing latitude, but the underlying mechanisms are ambiguous. Although both local and large-scale processes may drive this pattern, they act all through influencing species abundance distribution (SAD) and spatial pattern of species. A null model incorporating SAD is often used to calculate expected beta-diversity, which accounts for most variation in beta-diversity. However, a recent study has shown that the deviation of observed beta-diversity from expected values (beta-deviation) increases with latitude. The latitudinal gradients in beta-deviation may be related to both latitudinal differences in SADs and the degrees of spatial aggregation. Our study aims to (1) investigate how beta-deviation varies with SAD and spatial aggregation, and (2) separate the contributions of SAD and aggregation in explaining latitudinal gradients in beta-deviation.