Population genetic diversity of the endemic plant subspecies Ixeridium dentatum subsp. nipponicum (Asteraceae)

The plant Ixeridium dentatum subsp. nipponicum (Family Asteraceae) is an endemic species that inhabits the coastal area of Niigata, Japan. We surveyed natural habitats of this subspecies and evaluated the genetic diversity using simple sequence repeat (SSR) markers. Ten colonies were identified on the coastline of Niigata with the population size ranging from 15 to over 4000. Seven newly developed and three previously reported SSR markers detected 2-4 alleles in 421 individuals. The Shannon's diversity indexes were 0.812-0.967 without a particular relation to the population size, whereas the inbreeding coefficient ranged from −0.3 to 0.034 with three large-sized populations exhibiting near zero values. Furthermore, Bayesian and genetic distance analyses distinguished two colonies in the south side of Niigata from the other eight colonies. Thus, genetic diversity is fairly well maintained in various locations with a unique allele distribution pattern in the south corner of the habitat. We propose that the three habitats with a large population size will be preferentially protected and used as distribution centers of diverse genetic stocks.