Isolation and characterization of polymorphic microsatellite DNA markers in two shrew species, Sorex unguiculatus and S. caecutiens

We isolated six microsatellite markers from the partial genomic libraries of two Sorex shrews, S. unguiculatus and S. caecutiens, and examined their allelic variation. All loci showed high allelic variation ranging from 15 to 19 alleles and all but one locus conformed to Hardy-Weinberg expectations in the species where the loci were isolated. Cross-species amplifications showed that all primers derived from S. unguiculatus were useful for S. caecutiens, while among primer sets derived from S. caecutiens, only one was useful for S. unguiculatus. Accordingly, at least five microsatellite markers were useful in S. caecutiens and three in S. unguiculatus. 5 Naitoh et al. 3 To infer biogeographical history of an organism in detail, comparison of genetic structure among various local populations is essential. Recently, microsatellite markers have been routinely used to investigate genetic structure of natural populations in many species (Balloux and Lugon-Moulin 2002). With regard to soricine shrew some microsatellite primers have been designed for S. araneus (Wyttenbach et al. 1997). However, according to our preliminary study, only a few of their markers were useful for two Sorex species in north eastern Asia, S. unguiculatus and S. caecutiens, which are common in Hokkaido, the northernmost island of Japan (Ohdachi and Maekawa 1990). Here, we isolated new microsatellite loci from the genomes of these two Asian Sorex species and assessed their allelic variation in a natural population of each species. Cross-species amplification was also performed using the primer sets designed for the species where the loci were originally isolated. 5