Primula jesoana Miq. is a self-incompatible perennial herb found in the northern part of Japanese Archipelago. Although the species is relatively common in Hokkaido, it is persisting as only fragmented, small populations in Sado Island. In this study, we investigated the levels of genetic variation maintained within three remnant populations in the island, as well as reproductive success in these sites.

The numbers of ramets and flowering ramets were 107 and 75 in population A, 20 and 12 in population B, and 10 and 8 in population C, respectively. In population A, the numbers of short-styled ramets, long-styled ramets and ramets of unknown style-morph were 26, 11 and 38, respectively. The germination rates were 73% in population A, 33% in population B and 39 % in population C. The number of genets estimated using seven SSR loci were 33 (G/N: 0.77), 27 (G/N: 0.90) and 4 (G/N: 1.00), indicating high clonal diversity. The indices of genetic diversity were generally lower in Sado Island (allelic richness: 3.41; He: 0.346) than those observed in the large, continuous populations in Hokkaido (Ohtani et al., unpublished). These results may be because of the relatively isolated nature of the Island (ex. founder effect).