Phylogeography of the arid shrub Atraphaxis frutescens (Polygonaceae) in northwestern China: evidence from cpDNA sequences

Climatic fluctuations during the Pleistocene are usually considered as a significant factor in shaping intraspecific genetic variation and influencing demographic histories. To well-understand these processes in desert northwest China, we selected arid adapted Atraphaxis frutescens as the study species. Two cpDNA regions (psbK-psbI, psbB-psbH) were sequenced in 272 individuals from 33 natural populations across the range of this shrub, and 10 haplotypes were identified. It was found to contain high levels of total gene diversity (H T = 0.858), and low levels of within-population diversity (H S = 0.092). Analysis of molecular variance (AMOVA) indicates that genetic differentiation primarily occurs among groups of populations. Based on BEAST (Bayesian Evolutionary Analysis Sampling Trees) analysis, we suggest that intraspecific differentiation of the species, resulting from isolated populations, accompanied enhanced desertification during the middle and late Pleistocene. The expansion of ...