Where winter rules: Modeling wild boar distribution in its north-eastern range.

Wild boars are distributed almost all over the Earth. Though, Northern Asia remained not inhabited by the species until the end of the 20th century. In the last two decades slowly but surely the wild boar has expanded the northeastern edge of its range to the northern border of the taiga. Investigating environmental factors that underlie range expansions is crucial for understanding its mechanism and predict future changes in species distribution and biodiversity. Here we investigated the distribution of wild boar in its northeastern range, comparing the role of habitat and climate variables at three spatial scales: the permanently occupied area, the area of potential expansion and the total area. We have shown that along the gradient of wild boar occupancy (from permanently to sporadically occupied to presently unoccupied) the importance of habitat variables decreases while importance of climatic variables increases. Our analysis suggests that the potential range increase of the species results from the combined effect of habitat and climatic variables. A possibility for future expansion, however, is rather related to climate change (particularly to the increase of temperature at high latitudes) than to the alteration of habitat or shifts in resource use.