Ice age distributions of European small mammals: insights from species distribution modelling

In addition to the traditionally recognized Last Glacial Maximum (LGM, 21 ka) refuge areas in the Mediterranean region, more northerly LGM distributions for temperate and boreal taxa in central and eastern Europe are increasingly being discussed based on palaeoecological and phylogeographical evidence. Our aim was to investigate the potential refuge locations using species distribution modelling to estimate the geographical distribution of suitable climatic conditions for selected rodent species during the LGM. Eurasia. Presence/absence data for seven rodent species with range limits corresponding to the limits of temperate or boreal forest or arctic tundra were used in the analysis. We developed predictive distribution models based on the species present-day European distributions and validated these against their present-day Siberian ranges. The models with the best predictors of the species distributions across Siberia were projected onto LGM climate simulations to assess the distribution of climatically suitable areas. The best distribution models provided good predictions of the present-day Siberian ranges of the study species. Their LGM projections showed that areas with a suitable LGM climate for the three temperate species (Apodemus flavicollis, Apodemus sylvaticus and Microtus arvalis) were largely restricted to the traditionally recognized southern refuge areas, i.e. mainly in the Mediterranean region, but also southernmost France and southern parts of the Russian Plain. In contrast, suitable climatic conditions for the two boreal species (Clethrionomys glareous and Microtus agrestis) were predicted as far north as southern England and across southern parts of central and eastern Europe eastwards into the Russian Plain. For the two arctic species (Lemmus lemmus and Microtus oeconomus), suitable climate was predicted from the Atlantic coast eastward across central Europe and into Russia. Our results support the idea of more northerly refuge areas in Europe, indicating that boreal species would have found suitable living conditions over much of southern central and eastern Europe and the Russian Plain. Temperate species would have primarily found suitable conditions in the traditional southern refuge areas, but interestingly also in much of the southern Russian Plain.