Biogeography of European land mammals shows environmentally distinct and spatially coherent clusters

Zoogeography, the subdivision of geographical space into regional subunits based on their fauna, has been a core activity of biology at least since the time of Wallace (1876). Originally its emphasis was on entire faunas and geographical units at the subcontinental or regional level (see the comprehensive review in Udvardy, 1969), but progress in the understanding of the spatial dynamics of metapopulations (Hanski, 1999; Hanski & Caggiotti, 2004) has shifted the focus towards single species and local scales. However, the question of how species are distributed in time and space remains a central research theme at all levels of scaling. Indeed, Holt & Keitt (2005) have recently argued that species borders qualify as a ‘unifying theme’ in ecology. After reviewing the current understanding of single-species borders, they make a plea for research that HIIT Basic Research Unit, Laboratory of Computer and Information Science, Helsinki University of Technology, PO Box 5400, Helsinki, FI-02015 HUT, Finland, Department of Geology and Institute of Biotechnology, PO Box 64, University of Helsinki, Helsinki, FIN-00014, Finland, and HIIT Basic Research Unit, Department of Computer Science, PO Box 68, University of Helsinki, Helsinki, FIN-00014, Finland