Patterns of genetic variation in the Chinese endemic Psilopeganum sinense (Rutaceae) as revealed by nuclear microsatellites and chloroplast microsatellites

Psilopeganum sinense is a perennial herb endemic to Three-Gorges Reservoir Area (TGRA) in China. Genetic diversity of this endangered species was assessed by using 11 nuclear microsatellites and three chloroplast microsatellite (cpSSR) markers. A total of 8 haplotypes were identified in a survey of 212 individuals sampled from nine populations encompassing most of the natural range of the species. A low level of genetic diversity was detected: HE = 0.301 for SSR and HE = 0.28 for cpSSR. Populations were highly differentiated from one another: an AMOVA analysis that showed that 56.3% and 68.2% genetic variation resided between populations based on SSR and cpSSR analysis, respectively, and FST and FSTc (0.467 for SSR and 0.644 for cpSSR, respectively) were high. Significant differences were found between estimates of haplotypic differentiation calculated by using unordered alleles (GSTc = 0.857) and ordered alleles (NSTc = 0.728), which indicated the existence of phylogeographical structure in P. sinense. The indirect ratio of pollen flow/seed flow derived from estimates of haplotypic and nuclear DNA differentiation indicated that gene flow via pollen is less efficient than via seed. Two distinct evolutionary lineages (evolutionary significant units, ESUs) were recognized for P. sinense on the basis of both the PCoA and NCA analysis. Sampling strategies for conserving this endangered plant were discussed.