Polymorphism and genetic evolution in an isolate in the Antilles: Saint-Barthélémy

St Barthélémy, a small island near Guadaloupe, has been isolated since the eighteenth century. The population is made up of two geographical isolates, genetically separated. In each, the inbreeding level is increasing on account of random genetic drift, which is reinforced by village endogamy, equivalent to a kind of spouse selection. Consanguinity between spouses has been analysed to give an estimate of the contributions of random genetic drift and spouse choice to total inbreeding. A second estimate to inbreeding can be obtained from the variation in observed gene frequencies. The two estimates obtained are of the same order, 0.6-1.0%, and are comparable with those still observed in isolated villages of the French Pyrenees.