Clewing Catharina, Albrecht Christian, Wilke Thomas
Department of Animal Ecology and Systematics, Justus Liebig University Giessen, Giessen, Germany.
PLoS One. 2016 Aug 8;11(8):e0160286. doi: 10.1371/journal.pone.0160286. eCollection 2016.
Although only relatively few freshwater invertebrate families are reported from the Tibetan Plateau, the degree of endemism may be high. Many endemic lineages occur within permafrost areas, raising questions about the existence of isolated intra-plateau glacial refugia. Moreover, if such refugia existed, it might be instructive to learn whether they were associated with lakes or with more dynamic ecosystems such as ponds, wetlands, or springs. To study these hypotheses, we used pulmonate snails of the plateau-wide distributed genus Radix as model group and the Lake Donggi Cona drainage system, located in the north-eastern part of the plateau, as model site. First, we performed plateau-wide phylogenetic analyses using mtDNA data to assess the overall relationships of Radix populations inhabiting the Lake Donggi Cona system for revealing refugial lineages. We then conducted regional phylogeographical analyses applying a combination of mtDNA and nuclear AFLP markers to infer the local structure and demographic history of the most abundant endemic Radix clade for identifying location and type of (sub-)refugia within the drainage system. Our phylogenetic analysis showed a high diversity of Radix lineages in the Lake Donggi Cona system. Subsequent phylogeographical analyses of the most abundant endemic clade indicated a habitat-related clustering of genotypes and several Late Pleistocene spatial/demographic expansion events. The most parsimonious explanation for these patterns would be a scenario of an intra-plateau glacial refugium in the Lake Donggi Cona drainage system, which might have consisted of isolated sub-refugia. Though the underlying processes remain unknown, an initial separation of lake and watershed populations could have been triggered by lake-level fluctuations before and during the Last Glacial Maximum. This study inferred the first intra-plateau refugium for freshwater animals on the Tibetan Plateau. It thus sheds new light on the evolutionary history of its endemic taxa and provides important insights into the complex refugial history of a high-altitude ecosystem.
尽管据报道青藏高原的淡水无脊椎动物科相对较少，但特有程度可能很高。许多特有谱系出现在永久冻土区，这引发了关于高原内部孤立冰川避难所存在与否的疑问。此外，如果存在这样的避难所，了解它们是与湖泊相关，还是与池塘、湿地或泉水等更具动态性的生态系统相关，可能会有所启发。为了研究这些假设，我们以广泛分布于高原的萝卜螺属肺螺亚纲蜗牛为模型类群，并以位于高原东北部的董给错湖排水系统为模型地点。首先，我们利用线粒体DNA数据进行了全高原系统发育分析，以评估栖息在董给错湖系统中的萝卜螺种群的整体关系，从而揭示避难谱系。然后，我们结合线粒体DNA和核AFLP标记进行区域系统地理学分析，以推断最丰富的特有萝卜螺分支的局部结构和种群历史，从而确定排水系统内（亚）避难所的位置和类型。我们的系统发育分析表明，董给错湖系统中的萝卜螺谱系具有高度多样性。随后对最丰富的特有分支进行的系统地理学分析表明，基因型存在与栖息地相关的聚类，以及几个晚更新世的空间/种群扩张事件。对这些模式最简洁的解释可能是，董给错湖排水系统存在一个高原内部的冰川避难所，它可能由孤立的亚避难所组成。尽管潜在过程尚不清楚，但末次盛冰期之前和期间的湖面波动可能引发了湖泊和流域种群的最初分离。本研究推断出青藏高原上首个淡水动物的高原内部避难所。因此，它为青藏高原特有类群的进化历史提供了新的线索，并为高海拔生态系统复杂的避难历史提供了重要见解。
