MICROSATELLITE EVOLUTION IN CONGENERIC MAMMALS - DOMESTIC AND BIGHORNSHEEP

We compared genotypes at eight (AC)n microsatellite loci in domestic s heep (Ovis aries) and wild Rocky Mountain bighorn sheep (O. canadensis ). The domestic sheep had greater genetic variation, higher allele-siz e variances, and larger allele sizes than the wild sheep. Accumulating evidence from higher taxonomic comparisons shows that these parameter s are biased if microsatellite loci are selected in one taxon and used in another. Our results demonstrate similar biases between congeneric species. We compared standard measures of genetic variation, differen tiation, and distance within and between species (H, D, F-ST) to newer measures based on allele-size variance (S-W, S-B, R(ST)). The size-ba sed distances better detected species-level divergence, but standard m easures better distinguished allopatric populations. Empirical calibra tion of these measures at the subspecies level is needed to establish their useful ranges.