Biogeographical connections between the Maghreb and the Mediterranean peninsulas of southern Europe

Abstract

The glacial-interglacial cycles have caused severe range modifications of species' distributions. In Europe, thermophilic species had to retreat into geographically distinct southern refugia during glaciations. This process produced strong genetic imprints, which are still detectable by the present pattern of genetic differentiation and the distribution of regional diversity. To reveal the biogeographical imprints in the western Mediterranean, we analysed 26 populations of the butterfly Maniola jurtina spread over large areas of its European and North African distribution range. The samples were analysed using allozyme electrophoresis. We detected three genetic groups, divided into Western Europe, Central/Eastern Europe, and Italy with the Maghreb. The North African samples randomly cluster within the Italian samples. Even the population sampled in Morocco is genetically closely related to these samples and not to the geographically neighbouring Iberian ones. Parameters of genetic diversity showed similar values over the whole study area. The observed genetic pattern reflects possible glacial refugia in Europe located in the Iberian Peninsula and the Balkans. For North Africa and Italy, our data reveal a colonization of Africa originating from Italy.

Population genetic structure of Juniperus phoenicea (Cupressaceae) in the western Mediterranean Basin: gradient of diversity on a broad geographical scale

“…africana (Romo and Boratyński 2007), found also at the genetic level using the RAPD and AFLP method (Jiménez et al 2003;Terrab et al 2008, respectively). Similar dependences have been found also in Abies species on the chloroplast DNA (Terrab et al 2007), and other organisms (for review see Weiss and Ferrand, 2007;Terrab et al 2008;Habel et al 2009 andOrtiz et al 2009). …”

“…Of particularly high influence was the Messinian Salinity Crisis, resulting in the connection of Europe and Africa (Krijgsman et al 1999;Schneck et al 2010;Jaromilo-Correa et al 2010). The link between Eurasian and African tectonic plates was coincident with an extremely dry climate, but served as an intercontinental pathway between both sides of the Mediterranean (Krijgsman et al 1999;Thompson 2005;Habel et al 2009;Schneck et al 2010). The separation of the Iberian Peninsula from Africa by the opening of the Strait of Gibraltar at the turn of the Miocene/Pliocene about 5 Myr BP (Krijgsman et al 1999) has likely created an impermeable barrier for plant migration (Terrab et al 2007(Terrab et al , 2008Habel et al 2009).…”

“…Cycles of population isolation/expansion left detectable genetic signatures, leading to a structured distribution of genetic diversity in natural populations across Europe. However, the Mediterranean basin constitutes not only a major Pleistocene refugium, but also a crossroads of plant migrations and a center of active speciation (Thompson 2005;Terrab et al 2007Terrab et al , 2008Habel et al 2009). In the Iberian Peninsula many populations followed "refugiawithin-refugia" scenario, which means they diverged without large geographical displacements producing intra-specific lineages often located in distinct allopatric refugia and exhibiting independent evolutionary histories (Gómez and Lunt 2007).…”

Role of the Mediterranean Sea in differentiating European and North African woodland bird assemblages

“…Indeed, such an extensive barrier to dispersal of biota may cause the differentiation of assemblages by limiting colonization across the barrier, and by facilitating speciation of isolated populations. Several studies confirmed speciation processes across the Strait of Gibraltar in multiple taxa, although the frequency of this phenomenon is greatly dependent on the dispersal abilities of each taxon; flying species, and those that tolerate salt water, tend to show lower levels of differentiation across the Strait (Habel et al 2009). Existing information is still insufficient to make broad generalizations about the level of permeability of the Strait for birds, but evidence indicates that it is lower in forest-adapted birds than in arid-adapted species .…”

“…Comparable conditions persisted even during the Pleistocene glacial periods and in fact southern Iberia and the adjacent areas of North Africa have been classically merged in the same glacial refuge, the Atlantic-Mediterranean centre (De Lattin 1949). In the case of birds, as in that of other flying organisms (Habel et al 2009), the Mediterranean remained a relatively permeable barrier, which partly prevented local differentiation processes and facilitated the homogenisation of the assemblages during this period.…”