Palaearctic biogeography revisited: evidence for the existence of a North African refugium for Western Palaearctic biota

Abstract

Aim: In contrast to the attention given to southern Europe both as a centre of speciation and differentiation and as a Pleistocene refugium of Western Palae- arctic taxa, North Africa has been relatively neglected. In this paper, we set out to address this shortfall. Location North-West Africa and the Mediterranean. Methods We reviewed the existing literature on the biogeography of North Africa, and carried out analyses of species distribution data using parsimony, nestedness and co-occurrence methods. Results In many cases, distribution patterns of non-flying mammals, bats, amphibians, reptiles, butterflies, zygaenid moths and odonates demonstrated important biogeographical affinities between Europe and North Africa at the species level. On the other hand, species co-occurrence, nestedness and parsi- mony analysis also revealed some deep splits between the Maghreb and Europe; yet even in these cases the closest affinities were found between the Iberian Peninsula and the Maghreb. Furthermore, North Africa harbours the highest proportion of endemic taxa (13.7%) across all groups analysed. Many molecu- lar studies demonstrated a strong genetic cohesiveness between North Africa and Europe despite the potential barrier effect of the Mediterranean Sea. In other taxa, however, remarkable splits were detected. In addition, southern European genetic lineages were often nested within North African clades, and many taxa showed exceptionally high genetic variability and differentiation in this region. Main conclusions The Maghreb was an important differentiation and specia- tion centre for thermophilic organisms during the Pliocene and Pleistocene with high relevance as a colonization source for Europe. The regions around the sea straits of Gibraltar and Sicily have acted as important biogeographical links between North Africa and Europe at different times.