Blood group polymorphisms and geography in the Sierra de Gredos, Spain.

The present research is designed to contribute to our knowledge of the influence of geography on the genetic population structure in the Sierra de Gredos (central Spain). This mountain range separates two distinct areas: the Tormes-Alberche valley in the north and the Tiétar valley in the south. Unrelated blood donors (226), whose 4 grandparents were born in the study area, were tested for blood group markers (A1A2BO, RH, MNSs, Kell, P, and Lewis). R matrix analysis in relation to other Spanish populations agrees reasonably well with the cluster analysis of the Prevosti distance matrix using the UPGMA algorithm. Comparisons suggest a certain degree of genetic variation between the populations of these two valleys. The Sierra de Gredos can thus be considered a biological barrier limiting the gene flow between the valleys.