Abstract
Variations in genetic and morphological characteristics were investigated in two populations of the exotic pond loach, Paramisgurnus dabryanus, which has invaded rice fields in Kuma-kougen Town, Ehime Prefecture. A sequence analysis of the mitochondrial DNA control region of 46 individuals collectedf rom two sampling sites (Higashi-myoujin and Koudono, separation distance1.6 km) revealed two divergent clades (average nucleotide divergence: 15%)representing separate introductions: Group 1 (four haplotypes), related to P. dabryanus, and Group 2 (two haplotypes), related to Misgurnus anguillicaudatus, as a result of mitochondrial DNA introgression. In 29 of the 46 specimens, which included individuals of both genetic clades, four of 13 morphological characteristics(relative to body size) (head length, pre-pectoral length, dorsal fin base length and caudal peduncle depth) differed significantly (ANOVA, df 28, P 0.01-0.05)between populations, but not between genetic clades. Haplotype constitutions differed significantly between sampling sites (exact test, P 0.001), diversities being greater in Koudono which is located downstream of Higashi-myoujin. The existence of genetically divergent clades among the specimens suggested that the early introductions of this species to Japan originated from several localities.
