GEOGRAPHIC HOMOGENEITY AND NONEQUILIBRIUM PATTERNS OF MTDNA SEQUENCESIN TUSCANY, ITALY

The geographical distribution of 49 mtDNA sequences from 22 localities in Southern Tuscany, Italy, was studied by molecular analysis of vari ance, by a new spatial autocorrelation statistic specifically designed for sequence data and by reconstructing genealogies of haplotypes. Al l these methods indicated a high homogeneity of populations. Neverthel ess, genetic variability showed significant departure from equilibrium expectations, in agreement with the predicted effects of a population expansion. We suggest that a past population expansion that was proba bly associated with a migrational wave and with local gene flow betwee n localities prevented spatial structuring in Southern Tuscany.