Genetic diversity in the Japanese rosy bitterling, Rhodeus ocellatus kurumeus (Cyprinidae)

Comparison of meristic characters (pored lateral line scales, vertebrae, an d fin rays), and PCR-RFLP analysis in the D-loop and ND1 regions of mitocho ndrial DNA were performed to estimate the genetic diversity in local popula tions of the Japanese rosy bitterling, Rhodeus ocellatus kurumeus. In terms of meristic characters, the Fukuoka population was the largest in both ran ge and variance of the number of pored lateral line scales and vertebrae (a bdominal and caudal), and Osaka was the second, whereas the Kagawa populati on showed the smallest range and variance in these characters. In PCR-RFLP analysis, 11 haplotypes (3 in Fukuoka, 2 in Okayama, 2 in Kagawa, and 4 in Osaka) were observed, and nucleotide sequence divergence (NSD) was approxim ately two times larger in ND1 (mean, 0.61%) than in D-loop (mean., 0.31%). In the neighbor-joining (NJ) tree, based upon the NSD value in ND1, haploty pes were arranged into four clades, which corresponded to the locality of e ach haplotype. The Fukuoka population was conspicuously apart from the othe r populations (mean, 0.90% in NSD), but the remaining three showed a simila r genetic distance with each other (mean, 0.48%-0.52% in NSD). In haplotype diversity of mtDNA, half the stations in Osaka and all in Kagawa were mono morphic. Especially, two haplotypes endemic to Kagawa were randomly distrib uted, irrespective of drainages. Rhodeus o. kurumeus in Fukuoka inhabits sm all rivers and creeks (open water systems), while that in Kagawa and Osaka lives in small ponds (closed water systems). Taking the information of morp hology, mtDNA, and habitat into consideration, the low genetic diversity in Kagawa and Osaka populations of R. o. kurumeus is thought to be mainly the result of the isolation of their habitat.