Glaciation as an historical filter of below-ground biodiversity

Aim: The latitudinal gradient in species richness is one of the most studied biodiversity patterns. Here we explore a north–south gradient in earthworm diversity, and evaluate the importance of current and historical filters in shaping the distribution of present-day below-ground species richness. Location: France. Methods: Using high-resolution data on earthworm distributions across France, we document the latitudinal gradients in alpha (α), beta (β) and gamma (γ) diversity. We relate these gradients to species' traits, taxonomic aggregation and co-occurrence patterns, and correlate them with the present climate and the history of glaciation in Europe. Results: We found that γ-diversity decreases from south to north whereas α-diversity increases along the same latitudinal gradient. Communities in formerly glaciated regions are composed of smaller, more mobile species and show trait and taxonomical aggregation. In more southerly populations, which did not experience glaciation,...