MATING PATTERNS AND GENE DYNAMICS OF A POPULATION ISOLATE OF NATIVE-AMERICANS

Mating structure can have important effects on population genetic phen omena, including inbreeding and genetic drift. However, data necessary to test predictions based on mathematical models or identify sensitiv ity to simplifying assumptions are difficult to collect. We used two s ources of such data, pedigrees and genotypes, collected in a human-pop ulation isolate. The population studied was Native American and locate d in New Mexico. It was founded in the mid-19th century by ca. 30 indi viduals, primarily of Navajo origin, and its size increased steadily t hereafter. A complete tribal pedigree spanning ca. 100 years (up to 19 48) was collected by anthropologists starting in the 1920s. Probabilit ies of allelic identity by descent (IBD) within and among individuals were calculated for all generations directly from the pedigree. Wright 's F-statistics were calculated from the IBD probabilities, and N-e wa s obtained from the statistic F-ST. Genetic typings were performed on blood samples collected from the population between 1991-1993. A secon d set of F-statistics were calculated from genetic typings. Genetic ki nship between individuals (F-ST) and average inbreeding within individ uals (F-IT) stabilized after the first two generations. However, F-ST was always greater than F-IT of the next generation, suggesting that t he net effect of social practices was inbreeding avoidance. In contras t to general expectations for growing populations, N-e increased over generations due to immigration. F-statistics estimated from the geneti c typings were remarkably close to pedigree estimates, suggesting a dr ift-migration steady state.