Population genetic structure and phylogeographic patterns in the Chinese endemic speciesSagittaria lichuanensis, inferred from cpDNAatpB–rbcL intergenic spacers

Abstract

Both historical (e.g., glaciations) and spatial (geological features) factors are considered to have had significant influences on the distribution and genetic structure of many plants. To understand the effects of such factors on the current genetic and geographical distributions of plant species in the Nanling and central regions in China, we examined genetic variation and phylogeographical patterns of Sagittaria lichuanensis J.K. Chen (Alismataceae), an endangered and endemic species in China, using chloroplast DNA atpB–rbcL intergenic spacer sequence variation. In this study, a total of 9 haplotypes from 47 individuals in 6 populations of S. lichuanensis were detected. The NST(0.193) was significantly higher than GST(0.082) (P < 0.05), indicating a significant phylogeographical structure. In the minimum spanning network (MSN) of the haplotypes, the distribution of haplotypes showed an east–west split. The results of the Mantel test analysis showed that there was no correlation between the genetic distance and geographical distance (r = 0.539, P > 0.05). The formation of barriers to dispersal might have played an important role in shaping the population genetic structure of S. lichuanensis. Within each region (east and west regions), high levels of gene flow between populations and low levels of population differentiation were found. Several conditions, such as co-ancestry due to recent common ancestry or short period of isolation, might have occurred among the populations studied. In the MSN, all tip haplotypes except for two (A and G) occurred in two or more populations, and the haplotype D in the interior node was widespread. The haplotype D is likely to be an ancestral haplotype and represents the relic, widely distributed haplotype before the populations were fragmented and isolated by mountain uplift.