Alu insertion polymorphisms in NW Africa and the Iberian Peninsula: evidence for a strong genetic boundary through the Gibraltar Straits

David Comas, Francesc Calafell, Noufissa Benchemsi, Ahmed Helal, Gerard Lefranc, Mark Stoneking, Mark A. Batzer, Jaume Bertranpetit, Antti Sajantila

A1 Unitat de Biologia Evolutiva. Facultat de Ciències de la Salut i de la Vida. Universitat Pompeu Fabra. Doctor Aiguader 80. 08003 Barcelona, Catalonia, Spain
A2 Department of Forensic Medicine, P.O. Box 40, University of Helsinki, 00014 Helsinki, Finland
A3 Centre National de Transfusion Sanguine, 11400 Rabat, Morocco
A4 Faculté de Pharmacie de Monastir. 5019 Monastir. Tunisia
A5 CNRS UPR 1142 - Institut de Génétique Humaine et Université Montpellier II, 34095 Montpellier Cedex 5, France
A6 Max Planck Institute for Evolutionary Anthropology, Inselstrasse 22, D-04103 Leipzig, Germany
A7 Departments of Pathology, Biometry and Genetics, Biochemistry and Molecular Biology, Stanley S. Scott Cancer Center, Neuroscience Center of Excellence, Louisiana State University Health Sciences Center 1901 Perdido Street, New Orleans, LA 70112, USA


Abstract. An analysis of 11 Alu insertion polymorphisms (ACE, TPA25, PV92, APO, FXIIIB, D1, A25, B65, HS2.43, HS3.23, and HS4.65) has been performed in several NW African (Northern, Western, and Southeastern Moroccans; Saharawi; Algerians; Tunisians) and Iberian (Basques, Catalans, and Andalusians) populations. Genetic distances and principal component analyses show a clear differentiation of NW African and Iberian groups of samples, suggesting a strong genetic barrier matching the geographical Mediterranean Sea barrier. The restriction to gene flow may be attributed to the navigational hazards across the Straits, but cultural factors must also have played a role. Some degree of gene flow from sub-Saharan Africa can be detected in the southern part of North Africa and in Saharawi and Southeastern Moroccans, as a result of a continuous gene flow across the Sahara desert that has created a south-north cline of sub-Saharan Africa influence in North Africa. Iberian samples show a substantial degree of homogeneity and fall within the cluster of European-based genetic diversity.