Refugia within refugia:: patterns of phylogeographic concordance in the Iberian Peninsula

The Iberian Peninsula was one of the most important Pleistocene glacial refugia in Europe. A number of recent studies have documented the phylogeography of Iberian taxa and their relationship to more widely distributed species that expanded from this southern European refugium. We use a comparative approach to review the literature that challenges the paradigm of Iberia as a single refuge during Pleistocene glacial maxima and instead supports the occurrence of several Iberian refugia for a range of flora and fauna. Some patterns of phylogeographic concordance were found between the refugial areas identified by different case studies and these broadly overlapped with previously recognized areas of high endemism in the Iberian Peninsula. Such patterns help to illustrate the internal complexity of the Iberian Peninsula as a glacial refugium, and show that for many species, populations with a high degree of genetic structure have existed throughout the Pleistocene. Importantly, the occurrence of these 'refugia-within-refugia' may confound the interpretation of phylogeographic patterns of European species, and can misleadingly support the occurrence of northern refugia. We discuss these and other consequences, especially when a limited number of samples from the southern European refugia are used.