Abstract
Saussurea polylepis Nakai is an herbaceous perennial endemic to Korea and is highly restricted to several continental islands in the southwestern part of the Korean Peninsula. Given its very narrow geographical distribution, it is more vulnerable to anthropogenic activities and global climate changes than more widely distributed species. Despite the need for comprehensive genetic information for conservation and management, no such population genetic studies of S. polylepis have been conducted. In this study, genetic diversity and population structure were evaluated for 97 individuals from 5 populations (Gwanmaedo, Gageodo, Hongdo, Heusando, and Uido) using 19 polymorphic microsatellites. The populations were separated by a distance of 20–90 km. We found moderate levels of genetic diversity in S. polylepis (Ho = 0.42, He = 0.43). This may be due to long lifespans, outcrossing, and gene flow, despite its narrow range. High levels of gene flow (Nm = 1.76, mean Fst = 0.09), especially from wind-dispersed seeds, would contribute to low levels of genetic differentiation among populations. However, the small population size and reduced number of individuals in the reproductive phase of S. polylepis can be a major threat leading to inbreeding depression and genetic diversity loss. Bayesian cluster analysis revealed three significant structures at K = 3, consistent with DAPC and UPGMA. It is thought that sea level rise after the last glacial maximum may have acted as a geographical barrier, limiting the gene flow that would lead to distinct population structures. We proposed the Heuksando population, which is the largest island inhabited by S. polylepis, as a source population because of its large population size and high genetic diversity. Four management units (Gwanmaedo, Gageodo, Hongdo-Heuksando, and Uido) were suggested for conservation considering population size, genetic diversity, population structure, unique alleles, and geographical location (e.g., proximity).
Highlights
Population genetic studies often elucidate demographic histories and evolutionary processes in humans [1, 2], animals [3, 4], and plants [5,6,7]
19 polymorphic microsatellite markers were used to determine the genetic diversity of S. polylepis
Genetic indices of each population were summarized in Regions N number of alleles (Na) number of effective alleles (Ne) Ho He
Summary
Population genetic studies often elucidate demographic histories and evolutionary processes in humans [1, 2], animals [3, 4], and plants [5,6,7]. The precise levels of these characteristics are determined by the diversity of ecological habitats and the degree of geographic isolation from the mainland. Many prior studies have focused on patterns of speciation [16,17,18] and diversification [19] as well as comparisons of genetic diversity between mainland and island populations [20, 21]. Novel environmental conditions and small populations isolated by geographical barriers can lead to increased genetic differentiation [23] and new opportunities for allopatric speciation [24]
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