Genetic diversity and differentiation in Camellia reticulata (Theaceae) polyploid complex revealed by ISSR and ploidy

Camellia reticulata is a well-known ornamental and oil plant that is endemic to southwest China. This species shows three cell ploidies, i.e., diploidy, tetraploidy and hexaploidy. We made the first investigation of genetic diversity and differentiation of natural populations of C. reticulata, and 114 individuals from 6 populations were sampled. Cytogeography results showed that ploidy is invariable within populations and evenly distributed. A relatively high level of genetic diversity was found in C. reticulata, both at the species level (PPB = 88.89%; H = 0.2809; I = 0.4278) and at the population level (mean PPB = 42.13%; mean H = 0.14; mean I = 0.21). We found a relatively low degree of differentiation among ploidies (G(ST) = 0.2384; AMOVA = 10.26%) and a relatively high degree of differentiation among populations (G(CS) = 0.3807; AMOVA = 48.75%). The high genetic diversity can be explained by its biological character, wide distribution and ploidies, and the special genetic structure can be ascribed to polyploid origin from hybridization with different Camellia spp. This information will be useful for the introduction, conservation and further studies of C. reticulata and related species.