High Genetic Differentiation in Endangered Sedum ussuriense and Implications for Its Conservation in Korea

Sedum ussuriense Kom. (Crassulaceae) is a succulent perennial herb localized to rocky valleys in southeastern Korea. Although it is an important natural resource with high economic value as an ornamental plant, it is currently endangered because of land-use changes and illegal exploitation. To initiate a proper conservation plan, we selected four populations (Juwang, Okgye, Jeolgol, and Haok) around Mt. Juwang, characterized their phenotypic traits, and evaluated patterns of random amplified polymorphic DNA variation. Despite its small population size, Okgye had the greatest proportion of flowering plants and higher seed production than from the other populations. This population also harbored the greatest genetic diversity. However, recent fragmentation between Okgye and Haok appeared to cause genetic divergence, leading to close genetic relationships of Okgye to Juwang vs. Haok to Jeolgol. In the long term, this raises concerns about the loss of genetic variation and the possibility of a demographic crash in those fragmented populations. Because our results indicated a high degree of divergence among populations, we suggest that conservation activities should focus on maintaining and propagating all populations throughout this species’ range.