Population genetic structure and gene flow of Forsythia suspensa (Oleaceae) in Henan revealed by nuclear and chloroplast DNA

Forsythia suspensa (Thunb.) Vahl, is a climbing plant belonging to Oleaceae, which is widely distributed in China, North and South Korea and Japan. In this study, the genetic diversity of F. suspensa was analyzed using two noncoding chloroplast DNA regions (trnL-F and psbA-trnH) and nuclear ribosomal internal transcribed spacer (nrITS) with 60 individuals of Henan Province. A survey of nrDNA and cpDNA variation detected remarkably high levels of genetic diversity (nrDNA: h(T) = 0.478; cpDNA: h(T) = 0.806). As revealed by the results of AMOVA analysis, genetic differentiation for nrDNA (Phi(ST) = 0.110) was obviously lower than for cpDNA data (Phi(ST) = 0.937) in F. suspensa, gene flow among populations based on nrDNA (Nm = 2.02) was significantly higher than that based on cpDNA data (Nm = 0.02). Significant isolation-by-distance (IBD) for cpDNA was detected at the species-wide range (r = 0.548, P < 0.05), however, nonsignificant IBD for nrDNA was detected (r = 0.362, P > 0.05). On the basis of the genetic information, we propose LY and LJ populations should be conserved ex situ; however, JG and SS populations should be conserved in situ.