Abstract
In the south basin of Lake Biwa, Japan, the area and standing crops of submerged macrophyte vegetation were largely fluctuated due to the influence of human activities since 1930s. Vallisneria asiatica var. biwaensis (Hydrocharitaceae) is an endemic submerged macrophyte in the Lake Biwa-Yodo River system, Japan, and its populations have decreased in the south basin since the 1970s. In this study, population genetic structure of the species was analyzed to evaluate current status of the genetic variation and its relationship to the population reduction. A total of 447 samples from 19 populations, mainly located in the south basin, were genotyped at 14 allozyme loci. The levels of genetic variations in the south basin populations are almost consistent with that of the north basin populations. Low genetic differentiation among the populations suggests the occurrence of high gene flow, while the presence of population grouping along the coast was observed in the south basin. Our results demonstrated the limited relevance of the population reduction to its population genetic structure. However, protection of the genetic variability of the species is required from a conservation genetic viewpoint. The population genetic structure revealed in this study would be useful information in conservation program development.
