The contrasted evolutionary fates of deep-sea chemosynthetic mussels (Bivalvia, Bathymodiolinae)
The contrasted evolutionary fates of deep-sea chemosynthetic mussels (Bivalvia, Bathymodiolinae)
复制标题
深海化学合成贻贝（双壳纲、Bathymodiolinae）的对比进化命运
作者：
Justine Thubaut;N. Puillandre;Baptiste Faure;C. Cruaud;S. Samadi
Bathymodiolinae是在热液喷口发现的巨型贻贝，拥有化学合成共生体。由于它们与渗漏物种和来自有机基质的微小贻贝有着密切的系统发育关系，因此推测它们是从浅水环境逐渐进化到深水环境的，并专门在腐烂的有机残留物中，然后在渗漏中，最后定居在深海喷口。在这里，我们提出了一个多基因系统发育，揭示了大多数属是多系和/或并系。该系统的鲁棒性使我们能够修改属级分类。有机遗骸被有力地支持为Bathydiolinae的祖先栖息地。然而，而不是一个单一的步骤殖民化的喷口和渗漏，经常性的栖息地转移有机基板喷口和渗漏发生在进化过程中，从来没有相反。这一新的系统发育框架挑战了“由浅入深”的渐进式情景。来自有机遗骸的贻贝耐受各种生态条件，并显示出与喷口贻贝相反的惊人的物种多样性，尽管与喷口和渗漏相比，这种生境尚未得到充分开发。总的来说，我们的数据表明，对于深海贻贝来说，对喷口栖息地的高度专业化在这种恶劣的栖息地提供了生态成功，但也使该谱系进入了一种进化的死胡同。
Bathymodiolinae are giant mussels that were discovered at hydrothermal vents and harboring chemosynthetic symbionts. Due to their close phylogenetic relationship with seep species and tiny mussels from organic substrates, it was hypothesized that they gradually evolved from shallow to deeper environments, and specialized in decaying organic remains, then in seeps, and finally colonized deep-sea vents. Here, we present a multigene phylogeny that reveals that most of the genera are polyphyletic and/or paraphyletic. The robustness of the phylogeny allows us to revise the genus-level classification. Organic remains are robustly supported as the ancestral habitat for Bathymodiolinae. However, rather than a single step toward colonization of vents and seeps, recurrent habitat shifts from organic substrates to vents and seeps occurred during evolution, and never the reverse. This new phylogenetic framework challenges the gradualist scenarios “from shallow to deep.” Mussels from organic remains tolerate a large range of ecological conditions and display a spectacular species diversity contrary to vent mussels, although such habitats are yet underexplored compared to vents and seeps. Overall, our data suggest that for deep-sea mussels, the high specialization to vent habitats provides ecological success in this harsh habitat but also brings the lineage to a kind of evolutionary dead end.