Genetic Diversity, Divergence and Population Structure in the Japanese Freshwater Pearl Mussels Margaritifera laevis and M. togakushiensis

Abstract

Assessments of genetic diversity, divergence and population structure of two species of threatened freshwater pearl mussels, based on allelic frequencies of 16 allozyme loci and partial mitochondrial 16S rRNA sequences (489 bps) were conducted for 17 populations of Margaritifera laevis and six populations of M. togakushiensis on Hokkaido and Honshu Islands, Japan. No evidence of hybridization was apparent between the two species. Genetic diversity within populations and divergence among populations were somewhat higher in M. laevis than in other threatened congeners. In contrast, M. togakushiensis showed allozyme monomorphism. Although the two species differed in 10 bp substitutions in the examined region of the 16S rRNA gene, no sequence variations were evident within both species. Genetic diversity within these two species was relatively low when compared with those of bisexual freshwater clams and marine mollusks.