Endemic lake Baikal amphipods Transcriptome Shotgun Assembly project

Species flocks, large clades that have evolved from a common ancestor within a limited geographic range such as an ancient lake or isolated islands, provide splendid opportunities to study many aspects of evolution. Lake Baikal, which is at least 16 MY old and contains fully oxygenated depths of up to 1650m, harbors a unique fauna that includes several spectacular endemic species flocks (sponges, planarians, at least 3 groups of gastropods and, finally, amphipods). There are at least 250 described species of endemic Baikal amphipods that represent two independent invasions into Baikal. Baikal amphipods possess extreme morphological and ecological diversity. Morphologically, they include miniature and giant (up to 12cm) species, highly-armored, spiny species strikingly resembling unrelated marine forms and the unique planktonic amphipod Macrohectopus branickii. Ecologically, they range from typical generalist omnivorous/detritus-feeding species to highly specialized active predators, abyssal scavengers, plankton feeders, parasites or commensals of spongers and parasites of other amphipods. Thus, wide ecological diversification and high species richness make the adaptive radiation of Lake Baikal amphipods an excellent model system for adaptive research.

物种集群（species flock）指起源于同一共同祖先、演化形成且分布于古湖、孤立岛屿等有限地理范围内的大型演化支，为研究进化的诸多方面提供了绝佳契机。贝加尔湖（Lake Baikal）距今至少1600万年，其水深最大达1650米且全程含氧，孕育了独特的动物区系，其中包含多个极具特色的特有物种集群：海绵动物、涡虫、至少3类腹足类，以及端足类。目前已记述的贝加尔湖特有端足类物种至少有250种，该类群分两次独立入侵贝加尔湖。贝加尔湖端足类展现出极强的形态与生态多样性。形态上，它们涵盖微型与巨型（最大体长可达12厘米）物种、高度装甲化且具棘刺的类群（其形态与非近缘的海洋类群极为相似），以及独特的浮游端足类*Macrohectopus branickii*。生态上，其生态位跨度极广：从典型的广食性杂食/腐食物种，到高度特化的主动捕食者、深渊食腐者、浮游食性类群，以及寄生于海绵的共栖生物与寄生于其他端足类的寄生类群。因此，极高的生态多样性与物种丰富度，使得贝加尔湖端足类的适应性辐射成为开展适应性研究的优质模型系统。