Genetic structure and proposed conservation strategy for natural populations of Calycanthus chinensis Cheng and SY Chang (Calycanthaceae)

摘要

Calycanthus chinensis Cheng et S.Y. Chang, a tertiary relic species in China, is a shade-loving and deciduous bush with an elegant shape and beautiful flower of high ornamental value. It was widely planted in gardens and miniaturescapes in China. The objective of this study was to characterize the genetic variation and structure in the three extant populations of the species, in order to provide useful information for a future conservation strategy. Twenty-two of 120 RAPD primers were selected and a total of 257 stable and clear DNA fragments were scored. Calycanthus chinensis showed a lower level of genetic diversity. At the population level, the percentage of polymorphic loci, Nei's gene diversity and Shannon's information index were 40.9%, 0.1641 and 0.2386, respectively; while at the species level, the corresponding values were 59.1%, 0.2097 and 0.3123, respectively. The estimates of genetic differentiation based on Shannon's information index (0.2360), Nei's gene diversity (0.2175) and AMOVA (24.94%) were very similar, and significantly higher than the average genetic differentiation reported in outcrossed spermatophyte. So it suggested high genetic differentiation emerged among populations of C. chinensis. Genetic relationships among populations were assessed by Nei's standard genetic distance, which suggested that the Tiantai population was genetically distinct from the other two populations. Moreover, the genetic distance was significantly correlated with geographical distance among populations (r = 0.997, t > t(0.05)). The gene flow (N-m) was 0.8994, indicating that gene exchange among populations was restricted. A conservation strategy was proposed based on the low gene flow and habitat deterioration, which are contributing to the endangered status of this species.