Xu Zhe, Zhang Ming-Li
From the Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China (Xu and Zhang); The University of Chinese Academy of Sciences, Beijing, China (Xu); and Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China (Zhang).
J Hered. 2015 Mar-Apr;106(2):184-95. doi: 10.1093/jhered/esu078. Epub 2014 Dec 16.
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 the Gurbantunggut and Kumtag deserts in this area appears to have triggered divergence among populations of the western, central, and eastern portions of the region and shaped genetic differentiation among them. Two possible independent glacial refugia were predicted, the Ili Valley and the northern Junggar Basin. Extensive development of arid habitats (desert margin and arid piedmont grassland) coupled with a more equable climate because the early Holocene are factors likely to have generated recent expansion of A. frutescens.
更新世期间的气候波动通常被认为是塑造种内遗传变异和影响种群历史的一个重要因素。为了深入了解中国西北沙漠地区的这些过程，我们选择了适应干旱环境的灌木状木蓼作为研究物种。对该灌木分布范围内33个自然种群的272个个体的两个叶绿体DNA区域（psbK-psbI、psbB-psbH）进行了测序，共鉴定出10个单倍型。研究发现其总基因多样性水平较高（HT = 0.858），而种群内多样性水平较低（HS = 0.092）。分子方差分析（AMOVA）表明，遗传分化主要发生在种群组之间。基于贝叶斯进化分析采样树（BEAST）分析，我们认为该物种的种内分化是由孤立种群导致的，这一过程伴随着更新世中晚期沙漠化的加剧。该地区古尔班通古特沙漠和库姆塔格沙漠的扩张似乎引发了该地区西部、中部和东部种群之间的分化，并塑造了它们之间的遗传差异。预测了两个可能的独立冰川避难所，即伊犁河谷和准噶尔盆地北部。全新世早期干旱生境（沙漠边缘和干旱山麓草原）的广泛发展以及更为稳定的气候，可能是导致灌木状木蓼近期扩张的因素。
