ORIGINAL ARTICLE Glacial refugia for summer-green trees in Europe and south-west Asia as proposed by ECHAM3 time-slice atmospheric model simulations Suzanne A. G. Leroy 1* and Klaus Arpe 2 INTRODUCTION During the Quaternary, Europe lost some species of warm and cool deciduous trees (Bertini, 2003). These losses were greater than those in other continents (Leroy, 2007). During glacia- tions, most of these two groups of species survived in glacial refugia, called long-term refugia by Bennett et al. (1991). It is believed that most refugia were located in cool, moist mid- altitude mountain belts or in drought-prone, but warmer, valley bottoms such as the Danube (Leroy & Roiron, 1996; Svenning, 2003). Some boreal deciduous trees (e.g. Betula) and conifers had refugia at higher latitudes (Willis & van Andel, 2004). It is likely that extinctions of trees took place when populations were restricted to refugia during glacial periods, as the smaller populations were more easily affected by disease, competition and conditions too extreme for the ecological range of the species (Svenning, 2003; Leroy, 2007). It is essential to locate as many long-term refugia as possible, as they are often hot spots of biodiversity worth preserving for the future. Three approaches are possible: fossil pollen and charcoal sites dating from the Last Glacial Maximum (LGM), which are extremely rare, phylogeography (based on modern DNA) and climatic modelling, which is the approach devel- oped here. 1 Institute for the Environment, Brunel University, Uxbridge UB8 3PH, UK, 2 Max Planck Institute for Meteorology, Hamburg, Germany *Correspondence: Suzanne A. G. Leroy, Institute for the Environment, Brunel University, Uxbridge, UB8 3PH, UK. E-mail: suzanne.leroy@brunel.ac.uk ABSTRACT Aim To generate maps of potential refugia for summer-green trees during the Last Glacial Maximum (LGM). Locations Southern Europe and south-western Asia. Methods Time-slice simulations of the atmospheric climate with the ECHAM3 model are used for the LGM. Limiting factors beyond which cool and warm groups of deciduous trees cannot grow (such as temperature in growing degree days, minimum monthly temperature and precipitation in summer) are chosen. A limited validation by fossil pollen and charcoal records from LGM sites was done. Results Two sets of maps extending from Europe to the Caspian region for cool and warm summer-green trees are presented. Three criteria are combined using contour lines to indicate confidence levels. Small areas within the three southern peninsulas of Europe (Spain, Italy and Greece) are highlighted as possible refugia for summer-green trees. Further, areas that have remained poorly known are now proposed as refugia, including the Sakarya–Kerempe region in northern Turkey, the east coast of the Black Sea and the area south of the Caspian Sea. Main conclusions The maps produced in this study could be used to facilitate better long-term management for the protection of European and south-western Asian biodiversity. Keywords Biodiversity, climatic model, Europe, glacial refugia, LGM climate, palynology, summer-green trees. Journal of Biogeography (J. Biogeogr.) (2007) 34, 2115–2128 ª 2007 The Authors www.blackwellpublishing.com/jbi 2115 Journal compilation ª 2007 Blackwell Publishing Ltd doi:10.1111/j.1365-2699.2007.01754.x