Mediterranean Glacial Refugia

During the glacial periods, most thermophilic species became extinct over major parts of their former distribution range and only survived in "refugia" at lower latitudes which presented suitable climatic conditions. In Europe, these areas, located South of the transversal European high mountain systems, are the three well-studied refugial regions of the Mediterranean peninsulas (Iberia, Italy, and Balkans), all

Musée national d'histoire naturelle, Section Zoologie des Invertébrés, L-2160, Luxembourg, Luxembourg;

University of Trier, Department of Biogeography, D-54296 Trier, Germany e-mail: [email protected]

T. Schmitt

University of Trier, Biogeography, D-54296 Trier, Germany C. Drees and T. Assmann

Institute of Ecology and Environmental Chemistry, Leuphana University Lüneburg, Scharnhorststrasse 1, D-21335 Lüneburg, Germany

J.C. Habel and T. Assmann (eds.), Relict Species: Phylogeography and Conservation Biology, 189 DOI 10.1007/978-3-540-92160-8_10, © Springer-Verlag Berlin Heidelberg 2010

more or less isolated from each other (Reinig 1937; de Lattin 1949; Huntley and Birks 1983; Bennett et al. 1991; Comes and Kadereit 1998; Hewitt 1996, 1999; Taberlet et al. 1998). The Maghreb and Asia Minor represent two further important areas in which thermophilic organisms survived the glacial periods (Busack 1986; Seddon et al. 2001, 2002; Harris et al. 2002; Seddon et al. 2002; Cosson et al. 2005; Fritz et al. 2006; Horn et al. 2006; Marmi et al. 2006; Weingartner et al. 2006; Habel et al. 2008). During these glacial periods, species differentiated into distinct genetic lineages, and repeated allopatric disjunctions reinforced these genetic differentiations, sometimes resulting in speciation events (Santucci et al. 1998; Habel et al. 2005). Subcenters have been postulated for these Mediterranean refugia (e.g., Reinig 1950); these have been tested by recent molecular analyses for the Balkans (Poulakakis et al. 2003, 2005; Parmakelis et al. 2006a, b Schmitt et al. 2006), Iberia (Harris et al. 2004; Martínez-Solano 2004; Carranza et al. 2006b), Southern Italy (Steinfartz et al. 2000; Seddon et al. 2001; Podnar et al. 2005; Canestrelli et al. 2006), and the Maghreb (Cosson et al. 2005; Carranza et al. 2006a,b; Fritz et al. 2006).

In the wake of climate warming during the postglacial period, the species expanded their distribution ranges from these refugia into higher altitudes and latitudes. These movements generally followed four paradigm patterns (Hewitt 2000; Habel et al. 2005): (1) postglacial expansion from all three Southern European differentiation centers, (2) expansion of the Western and Eastern lineages, with the Adriatic-Mediterranean lineage being trapped in Italy by the Alps, (3) expansion of the Adriatic- and Pontic-Mediterranean lineages, but trapping of the Atlantic-Mediterranean lineage by the Pyrenees, and (4) major expansion to Central Europe only from the Balkans, and trapping of the Atlantic- and Adriatic-Mediterranean lineages by the Pyrenees and Alps, respectively. These patterns are frequently repeated in many animal and plant species.

These recolonizations resulted in secondary contact and hybrid zones which can be traced by sensitive molecular markers (Hewitt 1988, 1993). Five regions of Europe are known for their high number of hybrid zones: (1) the Alps, (2) the Pyrenees, (3) Western Central Europe, (4) Eastern Central Europe, and (5) central Scandinavia (Taberlet et al. 1998; Hewitt 1999; Schmitt 2007). Further processes which occurred during colonization processes, such as the loss of genetic diversity due to stepping stone or leptokurtic range expansion, can be identified that help in the interpretation of the mode of past range change dynamics and the core areas of historical distribution areas (Hewitt 2001) (Fig. 1).

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