Strong phylogeographic pattern of cpDNA variation reveals multiple glacial refugia for Saruma henryi Oliv. (Aristolochiaceae), an endangered herb endemic to China

Saruma henryi Oliv. (Aristolochiaceae) is an endangered herb endemic to China. In this study, chloroplast microsatellites (cpSSRs) and sequences of the atpB-rbcL intergenic spacers were employed to reveal its genetic diversity and phylogeographic patterns. We detected high within-species genetic diversity (HT = 0.939 for cpSSR; HT = 0.862 for atpB-rbcL) and pronounced among-population genetic differentiation (HS = 0.182, GST = 0.811, RST = 0.9, FST = 0.93 for cpSSR; HS = 0.238, GST = 0.724, NST = 0.758, FST = 0.79 for atpB-rbcL) with a strong phylogeographic pattern (RST > GST, P < 0.01 for cpSSR; NST > GST, U = 0.25 for atpB-rbcL). Eleven haplotypes were distinguished by cpSSRs and atpB-rbcL intergenic spacers, respectively. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggested the existence of multiple localized glacial refugia in Mts. Qinling, eastern Mts. Bashan and the southeastern edge of Yunnan-Guizhou Plateau. Nested clade analysis (NCA) and population genetic analyses supported the limited gene flow (caused by low dispersal capacity and complex topography of its habitats) as the major factor responsible for the strong population differentiation and phylogeographic pattern. Past fragmentation and allopatric fragmentation were inferred as important processes responsible for the modern phylogeograhpic pattern. In addition, contiguous range expansions occurred in western Mts. Qinling and eastern Mts. Bashan.