Format: ORAL

Antonia Salces-Castellano1,2, Pablo Vargas3 and Fernando Ojeda4

1 Department of Biology, Ecology and Evolution, Université de Liège, Belgium 2 Unit of Evolutionary Biology & Ecology. Université Libre de Bruxelles, Belgium 3 Departamento de Biodiversidad y Conservación, RJB-CSIC, Madrid, Spain 4 Departamento de Biología-IVAGRO, Universidad de Cádiz, Spain

The Strait of Gibraltar is characterised by the diversity and uniqueness of its terrestrial flora. The floristic similarity between both sides of the Strait, together with the existence of some discontinuities, illustrates its biogeographical importance as a dispersal bridge/barrier. On the other hand, the Strait of Gibraltar has acted as a biogeographical refuge for flora from the Pleistocene glaciations. Many plant species found on both sides of the Strait are associated with sandy, very acidic and infertile soils. These include the heather Calluna vulgaris and Erica australis, characteristic species of the Mediterranean heathland or herriza. The Strait was an important glacial refuge for these species, followed by a post-glacial expansion along the western Iberian Peninsula. However, the Guadalquivir valley, dominated by clayey, non-acidic, fertile soils, would represent an edaphic barrier to the northward expansion of these acidophilic species. How did they overcome it? The phylogeographic analyses of these two heathland species were reviewed, and the geological and geomorphological literature of the Strait of Gibraltar region was examined. For both species, a certain genetic discontinuity is observed between the European area of the Strait and those of the rest of the Iberian Peninsula. In contrast, there is a striking genetic link between the W Iberian Peninsula and the African part of the Strait. Assuming a sea-level drop of about 140 m, the topography of the Strait of Gibraltar and the continental shelf of the Gulf of Cadiz, as well as the tectonic nature of their substrates, we suggest the existence of a glacial corridor between the African side of the Strait and the Portuguese Algarve. Confirmation of this Tingitano-Algarvian corridor using NGS approaches will help to clarify the role of the Strait of Gibraltar as a bridge or dispersal barrier in the geographical distribution of plants.