Glaciations, deciduous forests, water availability and current geographical patterns in the diversity of European Carabus species

Abstract

Aim: Current climate, biotic habitat provision and historical events are known drivers of diversity patterns. However, these three factors are seldom evaluated together. Here, we study the influence of climate, the distribution of deciduous forests and Pleistocene climate changes on the species diversity of Carabus ground beetles in Europe. Location: Continental Europe. Methods: We used geographically weighted regressions (GWR) to explore geographical variation in the relationship between species richness and current climate in a spatially explicit context. Further, we analysed simultaneously the network of relationships among current temperature, climatic variability since the Last Glacial Maximum (LGM) and the distribution of deciduous forests through structural equation models (SEM). Also, we assessed dissimilarity in the composition of European faunas by means of beta diversity metrics related with true spatial replacement and nestedness. Results: We find that Carabus richness patterns are, at least in part, influenced by water–energy dynamics. However, the effects of current climate are also shaped by Pleistocene glaciations, as water and energy variables change in importance at the southern limits of the ice sheet during the LGM. Accordingly, this border results in abrupt shifts in the relative importance of both (1) current and past climate correlates on Carabus richness, and (2) nestedness and true turnover on the compositional changes among their assemblages. Moreover, we also detect a direct effect of the geographical distribution of deciduous forests on Carabus species richness in both northern and southern regions. Main conclusions: Our results confirm that the processes shaping diversity patterns may depend on the history of particular regions. While Carabus richness seems to be largely driven by current climate in southern Europe, in the north it appears to be more affected by the imprint of past climates. Our findings also suggest that the areas of influence of Pleistocene glaciations may depend on the idiosyncratic characteristics of particular taxa.