Shi Xiao-Jun, Zhang Ming-Li
Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi, 830011, Xinjiang, China,
J Plant Res. 2015 Mar;128(2):269-82. doi: 10.1007/s10265-014-0699-y. Epub 2015 Jan 28.
Zygophyllum xanthoxylon, a desert species, displaying a broad east-west continuous distribution pattern in arid Northwestern China, can be considered as a model species to investigate the biogeographical history of this region. We sequenced two chloroplast DNA spacers (psbK-psbI and rpl32-trnL) in 226 individuals from 31 populations to explore the phylogeographical structure. Median-joining network was constructed and analysis of AMOVA, SMOVA, neutrality tests and distribution analysis were used to examine genetic structure and potential range expansion. Using species distribution modeling, the geographical distribution of Z. xanthoxylon was modeled during the present and at the Last Glacial Maximum (LGM). Among 26 haplotypes, one was widely distributed, but most was restricted to either the eastern or western region. The populations with the highest levels of haplotype diversity were found in the Tianshan Mountains and its surroundings in the west, and the Helan Mountains and Alxa Plateau in the east. AMOVA and SAMOVA showed that over all populations, the species lacks phylogeographical structure, which is speculated to be the result of its specific biology. Neutrality tests and mismatch distribution analysis support past range expansions of the species. Comparing the current distribution to those cold and dry conditions in LGM, Z. xanthoxylon had a shrunken and more fragmented range during LGM. Based on the evidences from phylogeographical patterns, distribution of genetic variability, and paleodistribution modeling, Z. xanthoxylon is speculated most likely to have originated from the east and migrated westward via the Hexi Corridor.
霸王，一种荒漠植物，在中国西北干旱地区呈现出东西向连续分布的广泛格局，可被视为研究该地区生物地理历史的模式物种。我们对来自31个种群的226个个体的两个叶绿体DNA间隔区（psbK - psbI和rpl32 - trnL）进行了测序，以探究系统发育地理结构。构建了中介邻接网络，并使用AMOVA、SMOVA、中性检验和分布分析来检验遗传结构和潜在的范围扩张。利用物种分布模型，对霸王在当前和末次盛冰期（LGM）的地理分布进行了建模。在26个单倍型中，一个广泛分布，而大多数局限于东部或西部区域。单倍型多样性水平最高的种群位于西部的天山及其周边地区，以及东部的贺兰山和阿拉善高原。AMOVA和SAMOVA表明，总体而言，该物种缺乏系统发育地理结构，推测这是其特殊生物学特性的结果。中性检验和失配分布分析支持该物种过去的范围扩张。将当前分布与LGM时期的寒冷干燥条件进行比较，霸王在LGM时期的分布范围缩小且更加破碎。基于系统发育地理格局、遗传变异分布和古分布模型的证据，推测霸王最有可能起源于东部，并通过河西走廊向西迁移。
