Genetic structure of La Cabrera, Spain, from surnames and migration matrices

The genetic structure of La Cabrera (province of Léon, Spain), a highly isolated and inbred population (alpha3 = 0.00482), is analyzed by applying multivariate methods (nonmetric multidimensional scaling, Mantel test, Monmonier's algorithm) to different biodemographic data sets. Isonymy, parent-offspring migration (total, males, females), and marital migration matrices were obtained from 5,714 marriages recorded in 37 parishes (clustered in 4 municipalities) between 1880 and 1989. The aim of the study is to investigate the relationships between the genetic and geographic structures of the area. Endemicity values (diagonal of parent-offspring migration matrices), calculated for both sexes at two hierarchical levels (parishes and municipalities), show that female mobility follows the virilocal migration model at the higher (municipalities) level and the uxorilocal model at the parish level. Analysis of isonymy and parent-offspring migration matrices shows high correspondence between the genetic structure and geographic location of the parishes. In fact, the main reproductive barriers, constructed using Monmonier's algorithm, generally coincide with geographic barriers, highlighting increasing isolation patterns from northwest to southeast. Moreover, the analysis of isonymous relationships, which are influenced by earlier population movements, identifies three parishes whose outlier positions are explained by historical-cultural or geographic reasons. The positive and highly significant values (0.32 < or = r < or = 0.51;p < or = 0.001) given by the Mantel tests underline the dependence of the genetic structure on geographic distance. In confirmation of the endemicity results, the lowest correlation value (r = 0.32) is given by the female migration matrix. When the outlier parishes are omitted from the analysis, the correlation between isonymy and geographic distance increases from 0.35 to 0.46, and the values from the other migration matrices remain unchanged. In conclusion, the combination of different data sets and methods allows a wider and more coherent reconstruction of the historical changes in the genetic structure of the La Cabrera population.