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 Sie rra de Gredos (central Spain). This mountain range separates two disti nct areas: the Tormes-Alberche valley in the north and the Tietar vall ey in the south. Unrelated blood donors (226), whose 4 grandparents we re born in the study area, were tested for blood group markers (A1A2BO , RH, MNSs, Kell, P, and Lewis). R matrix analysis in relation to othe r Spanish populations agrees reasonably well with the cluster analysis of the Prevosti distance matrix using the UPGMA algorithm. Comparison s suggest a certain degree of genetic variation between the population s of these two valleys. The Sierra de Gredos can thus be considered a biological barrier limiting the gene flow between the valleys.