A possible hybrid zone in the Mytilus edulis complex in Japan revealed by PCR markers

Abstract

The adhesive protein allele of mussels collected at 13 points in Japan from Hokkaido to Kyushu was analyzed by the polymerase chain reaction using a set of primers which amplifies a part of the nonrepetitive region of the adhesive protein gene. While most mussels exhibited a 126 bp fragment, characteristic of the pure Mytilus galloprovincialis, 55 of 64 mussels sampled at Hiura and 1 of 14 mussels at Hakodate Port exhibited 168 and 126 bp fragments. Sequence analysis of the two fragments indicated that the 168 and 126 bp fragments are almost identical to previously reported sequences in M. trossulus and M. galloprovincialis, respectively. Since the frequency of heterozygous individuals in Hiura is very high, it is unlikely that they are simple hybrids. However, it is evident that mixing of genes occurred between the two species off Hokkaido.