GENETIC DISTINCTIVENESS OF A VILLAGE POPULATION OF HOUSE MICE - RELEVANCE TO SPECIATION AND CHROMOSOMAL EVOLUTION

A population of house mice, Mus musculus domesticus, from the village of Migiondo was found to be genetically distinct from nearby populatio ns in Upper Valtellina (Italian Alps). At the supernatant malic enzyme locus, Mod1, the only alleles found in Migiondo (c and n2) were virtu ally absent from the other populations in the valley, which were chara cterized by allele a. The extraordinary genetic distinctiveness of the Migiondo population is apparently the result of genetic drift, perhap s coupled with a founder event, and attests to the existence of nearly impenetrable geographic barriers around the village isolating it from other settlements only a few hundred metres away. The Mod1 features o f the house mice in Migiondo are reminiscent of the characteristics of house mice on maritime islands. The genetic confirmation of the geogr aphic isolation of Migiondo is of interest because there is evidence t hat this village may have been the site of recent speciation and extin ction events. The data are also of significance given the phenomenal c hromosomal variation in house mice from the vicinity of the Alps. It h as frequently been proposed that genetic drift/founder events are of i mportance in the fixation of chromosomal rearrangements; this study pr ovides the first direct evidence for their occurrence in alpine mouse populations.