AFLP analysis of genetic diversity in three populations of ayu Plecoglossus altivelis

The genetic diversity among three populations of ayu was analyzed by using fluorescence-based AFLP. Eight fish were collected from each of three locat ions representing native populations of the amphidromous form (AM), the lan dlocked form (LL), and the subspecific population from the Kawauchi River o n Amami-oshima Island (RK). A total of 745 DNA fragments were scored using 19 arbitrarily chosen primer combinations, based on the restriction enzymes MseI and EcoRI with three and two base pair extensions, respectively. The proportions of polymorphic genes and the average heterozygosity were, respe ctively, 0.550 and 0.107 for AM, 0.521 and 0.095 for LL, and 0.135 and 0.02 2 for RK. The band-sharing coefficients were 0.839 for AM, 0.853 for LL, an d 0.970 for RK. Genetic variation in each population varied directly with p opulation size. The RK population, which is considered in danger of extinct ion, showed very low polymorphism. Nei's genetic distance was 0.017 between AM and LL, 0.410 between AM and RK, and 0.414 between LL and RK. These res ults suggest that AFLP markers provide useful data for the evaluation of ge netic variability and divergence in fish.