Evolution of microsatellite alleles in four species of mice (genus Apodemus)

Microsatellite length variation was investigated at a highly variable micro satellite locus in four species of Apodemus. Information obtained from micr osatellite allele sequences was contrasted with allele sizes, which include d 18 electromorphs. Additional analysis of a 400-bp unique sequence in the flanking region identified 26 different haplotype sequences or "true" allel es in the sample. Three molecular mechanisms, namely, (1) addition/deletion of repeats, (2) substitutions and indels in the flanking region, and (3) m utations interrupting the repent, contributed to the generation of allelic variation. Size homoplasy can be inferred for alleles within populations, f rom different populations of the same species, and from different species. We propose that microsatellite flanking sequences may be informative marker s for investigating mutation processes in microsatellite repeats as well as phylogenetic relationships among alleles, populations, and species.