Conquest of the deep, old and cold: an exceptional limpet radiation in Lake Baikal

Lake Baikal is the deepest, oldest and most speciose ancient lake in the world. The lake is characterized by high levels of molluscan species richness and endemicity, including the limpet family Acroloxidae with 25 endemic species. Members of this group generally inhabit the littoral zone, but have been recently found in the abyssal zone at hydrothermal vents and oil-seeps. Here, we use mitochondrial and nuclear data to provide a first molecular phylogeny of the Lake Baikal limpet radiation, and to date the beginning of intra-lacustrine diversification. Divergence time estimates suggest a considerably younger age for the species flock compared with lake age estimates, and the beginning of extensive diversification is possibly related to rapid deepening and cooling during rifting. Phylogenetic relationships and divergence time estimates do not clearly indicate when exactly the abyssal was colonized but suggest a timeframe coincident with the formation of the abyssal in the northern basin...

贝加尔湖是世界上最深、最古老且物种多样性最丰富的古湖。该湖以软体动物物种丰富度高和特有性强为特征，其中包括笠贝科（Acroloxidae），该科有25个特有物种。该类群成员通常栖息于沿岸带（littoral zone），但近期在深海热泉和油渗漏点的深渊带（abyssal zone）也有发现。本研究利用线粒体和核基因数据，首次构建了贝加尔湖笠贝辐射演化的分子系统发育树，并测定了湖内多样化起始的时间。分化时间估算结果显示，该物种群的年龄显著小于贝加尔湖的估算年龄，而大规模多样化的起始可能与裂谷作用期间的快速加深和冷却有关。系统发育关系和分化时间估算虽未明确指出深渊带被定殖的具体时间，但提示其时间范围与北部盆地深渊带的形成时期相吻合...