Genetic diversity and population structure of the endangered and medically important Rheum tanguticum (Polygonaceae) revealed by SSR Markers

Rheum tanguticum (Polygonaceae), an endangered plant, is endemic to the Qinghai-Tibetan Plateau. A total of 114 individual of R. tanguticum from 10 geographically separate populations were analyzed using seven pairs simple sequence repeats (SSR) markers. 102 alleles were recorded, with an average of 14.6 alleles per locus (ranging from 13 to 17) and the expected heterozygosity (He) ranged from 0.384 to 0.515 (average 0.459). The genetic differentiation between populations was relatively high (Fst = 0.249); the gene flow (Nm = 0.754), however, was limited, which suggested that around 21.18% of the total genetic variations occurred between populations. Our results revealed high levels of genetic variations within and between populations. The endangered status of this species is probably due to harvesting of the wild populations, rather than a lack of the genetic diversity. Anthropologic effects as well as other factors may, together, have shaped the genetic structure of this species.