Does vicariance shape biotas? Biogeographical tests of the vicariance model in the north‐west European land snail fauna

Aim  To investigate the importance of vicariance in shaping the north‐west European land snail fauna. Location  North‐west Europe. Methods  We tested whether there is a non‐random congruence, i.e. a clustering of species ranges, using a Monte Carlo procedure with a null model that generates range data sets such that their range size distribution, the species richness distribution of the geographic cells and the spatial autocorrelation of the occurrences of a taxon approach the parameters in the real data set. Biotic elements, groups of species with similar ranges, were delimited with Model based Gaussian clustering. The prediction that closely related species belong to different biotic elements, has been tested with a chi‐square test. Results  The distribution areas of the north‐west European land snail species are significantly clustered as predicted by the vicariance model. One widespread and seven regional biotic elements were identified. Contrary to the predictions of the vicariance model, closely related north‐west European land snail species belong significantly more often to the same biotic element than should be expected by chance. Main conclusions  The clustering of closely related north‐west European land snail species within the same biotic element indicates that speciation modes other than vicariance were frequent or that the imprint of vicariance on the ranges was obscured by extensive post‐speciational dispersal. Extensive dispersal may have been caused by Pleistocene climatic fluctuations. The core areas of the regionally restricted biotic elements might indicate the positions of glacial refugia of land snails.