Abstract
To evaluate the condition of populations of the threatened aquatic plant Nymphoides peltata in Japan, we investigated the vegetation area, composition of floral morphs (long-, short-, or homo-styled morphs), and genetic diversity using ten microsatellite loci for all known subpopulations. Sixty-four subpopulations were identified in 27 river systems. Only 1 of the 33 subpopulations where flowers were detected had both long- and short-styled morphs and a relatively high potential for sexual reproduction; it was located in Lake Kasumigaura. Using microsatellites, 61 genets were detected in the subpopulations. The genetic data suggest that each N. peltata subpopulation in Japan is at high risk of extinction because of the low genet diversity and low sexual productivity. The subpopulation that had both floral morphs consisted of ten genets, which suggests the importance of sexual reproduction to the preservation of genet diversity. In an amendment of the Japanese Red List in 2007, this species was reclassified from vulnerable to near-threatened. However, our study suggested that the species should be conserved as a vulnerable species.
