Populations of Asarum mandshuricum are Strongly Differentiated Despite a High Outcrossing Rate

摘要

Asarum mandshuricum is a perennial herb that inhabits the herb layer of a forest. This species has life-history traits and distribution patterns that could negatively affect genetic diversity such as small population size, sparse distribution of populations, self-compatible flower, and short seed dispersal distance. Due to these traits, there are concerns about genetic drift and fragmentation by restricted gene flow, thus decreasing the fitness of the population. To identify genetic structures of A. mandshuricum and suggest main factors that determine its genetic structures, outcrossing rate and inhabitation pattern were investigated. Population size of this species was very small (15.2 individuals). Its outcrossing rate was high (t(m): 0.980). Genetic diversity of population was also high (h: 0.275, I: 0.421). Its cross-pollination rate, rather than distribution traits such as population size and insufficient connectivity among populations, was the main factor in determining genetic diversity. Despite high outcrossing rate, populations of A. mandshuricum were strongly differentiated (G(st): 0.492). Inhabitation with a limited gene flow through generation in the same place might have caused A. mandshuricum populations to have differentiated genetic structure. To preserve its populations and maintain genetic diversity, conservative efforts such as retaining population size and establishing connections between subpopulations are needed.