Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
Mol Phylogenet Evol. 2013 Sep;68(3):398-409. doi: 10.1016/j.ympev.2013.04.012. Epub 2013 Apr 27.
Lagochilus occurs in the arid zones across temperate steppe and desert regions of Northwest China. Cooling with strong dessication in the Pleistocene, along with rapid uplift of mountain ranges peripheral to the Qinghai-Tibet Plateau, appear to have had major impacts on the genetic structure of the flora. To understand the evolutionary history of Lagochilus and the divergence related to these past shifts of habitats among these regions, we sequenced the plastid intergenic spacers, psbA-trnH and trnS-trnG from populations throughout the known distributions of ten species of the genus. We investigated species-level phylogeographical patterns within Lagochilus. Phylogenetic trees were constructed using Neighbor-joining and Bayesian inference. The divergence times of major lineages were estimated with BEAST and IMa. Genetic structure and demographic history were inferred by AMOVA, neutrality tests, mismatch distribution, and Bayesian skyline plot analyses. The results showed that most chloroplast haplotypes were species-specific, and that the phylogeny of Lagochilus is geographically structured. The estimated Bayesian chronology and IMa suggested that the main divergence events for species between major eastern and western portions of the Chinese desert occurred at the Plio-/Pleistocene boundary (ca. 2.1-2.8 Ma ago), and likely coinciding with the formation of these deserts in Northwest China. The regional demographic expansions, in the western region at ca. 0.39 Ma, and in the eastern at ca. 0.06 Ma, or across all regions at ca. 0.26 Ma, showed the response to aridification accompanied by cooling of the Pleistocene sharply increased aridity in the Chinese deserts, which reflects a major influence of geologic and climatic events on the evolution of species of Lagochilus. We suggest that diversification is most likely the result of the past fragmentation due to aridification; the expansion of the range of species along with the deserts was an adaptation to dry and cold environments during the Quaternary.
沙生齿唇兰分布于中国西北干旱地区的温带草原和荒漠地区。更新世期间的强烈干燥和青藏高原周边山脉的快速抬升，似乎对该植物区系的遗传结构产生了重大影响。为了了解沙生齿唇兰的进化历史以及这些地区过去生境变化导致的物种分化，我们对分布于十个种的居群的质体基因间隔区 psbA-trnH 和 trnS-trnG 进行了测序。我们调查了沙生齿唇兰属内的种级系统地理格局。使用邻接法和贝叶斯推断构建了系统发育树。使用 BEAST 和 IMa 估计了主要谱系的分歧时间。通过 AMOVA、中性检验、不匹配分布和贝叶斯天空线图分析推断了遗传结构和种群历史。结果表明，大多数叶绿体单倍型是种特异性的，沙生齿唇兰的系统发育是地理结构的。估计的贝叶斯年代表和 IMa 表明，中国沙漠东西两部分之间的物种主要分歧事件发生在上新世/更新世边界（约 210-280 万年前），可能与中国西北沙漠的形成同时发生。西部地区约 39 万年前、东部地区约 6 万年前或所有地区约 26 万年前的区域种群扩张表明，对更新世冷却伴随干旱化的响应，使中国沙漠的干旱急剧增加，这反映了地质和气候事件对沙生齿唇兰属物种进化的重大影响。我们认为，多样化最有可能是过去由于干旱化导致的碎裂的结果；物种范围的扩张伴随着沙漠的扩张，是对第四纪干旱和寒冷环境的适应。
