Aquatic adaptation and depleted diversity: a deep dive into the genomes of the sea otter and giant otter

Despite its recent invasion into the marine realm, the sea otter (Enhydra lutris) has evolved a suite of adaptations for life in cold coastal waters, including limb modifications and dense insulating fur. This uniquely dense coat led to the near-extinction of sea otters during the 18th-20th century fur trade and an extreme population bottleneck. We used the de novo genome of the southern sea otter (E. l. nereis) to reconstruct its evolutionary history, identify genes influencing aquatic adaptation, and detect signals of population bottlenecks. We compared the genome of the southern sea otter to the tropical freshwater-living giant otter (Pteronura brasiliensis) to assess common and divergent genomic trends between otter species, and to the closely related northern sea otter (E. l. kenyoni) to uncover population-level trends. We found signals of positive selection in genes related to aquatic adaptations, particularly limb development and polygenic selection on genes related to hair folli...

尽管海獭（Enhydra lutris）近期才迁入海洋领域，但它已演化出一系列适应寒冷沿海水域生活的特征，包括肢体结构改变和浓密的保温皮毛。这种独特的浓密皮毛导致海獭在18 - 20世纪的毛皮贸易中濒临灭绝，并形成了极端的种群瓶颈（population bottleneck）。我们利用南方海獭（E. l. nereis）的从头组装基因组（de novo genome）重建其演化历史，识别影响水生适应的基因，并检测种群瓶颈信号。我们将南方海獭的基因组与热带淡水生境的巨獭（Pteronura brasiliensis）进行比较，以评估水獭物种间共有的和分化的基因组趋势；同时与亲缘关系较近的北方海獭（E. l. kenyoni）比较，以揭示种群水平趋势。我们发现与水生适应相关的基因存在正选择（positive selection）信号，尤其在肢体发育相关基因中；此外，与毛囊相关的基因存在多基因选择（polygenic selection）信号……