Verheye Marie L, Backeljau Thierry, d'Udekem d'Acoz Cédric
Royal Belgian Institute of Natural Sciences, OD Taxonomy and Phylogeny, rue Vautier 29, 1000 Brussels, Belgium; Catholic University of Louvain-la-Neuve, Department of Biology, Marine Biology Laboratory, Croix du Sud 3 bte L7.06.04, 1348 Louvain-la-Neuve, Belgium.
Royal Belgian Institute of Natural Sciences, OD Taxonomy and Phylogeny, rue Vautier 29, 1000 Brussels, Belgium; University of Antwerp, Evolutionary Ecology Group, Universiteitsplein 1, 2160 Antwerp, Belgium.
Mol Phylogenet Evol. 2017 Sep;114:14-33. doi: 10.1016/j.ympev.2017.05.013. Epub 2017 May 18.
The Antarctic shelf's marine biodiversity has been greatly influenced by the climatic and glacial history of the region. Extreme temperature changes led to the extinction of some lineages, while others adapted and flourished. The amphipod genus Epimeria is an example of the latter, being particularly diverse in the Antarctic region. By reconstructing a time-calibrated phylogeny based on mitochondrial (COI) and nuclear (28S and H3) markers and including Epimeria species from all oceans, this study provides a temporal and geographical framework for the evolution of Antarctic Epimeria. The monophyly of this genus is not supported by Bayesian Inference, as Antarctic and non-Antarctic Epimeria form two distinct well-supported clades, with Antarctic Epimeria being a sister clade to two stilipedid species. The monophyly of Antarctic Epimeria suggests that this clade evolved in isolation since its origin. While the precise timing of this origin remains unclear, it is inferred that the Antarctic lineage arose from a late Gondwanan ancestor and hence did not colonize the Antarctic region after the continent broke apart from the other fragments of Gondwanaland. The initial diversification of the clade occurred 38.04Ma (95% HPD [48.46Ma; 28.36Ma]) in a cooling environment. Adaptation to cold waters, along with the extinction of cold-intolerant taxa and resulting ecological opportunities, likely led to the successful diversification of Epimeria on the Antarctic shelf. However, there was neither evidence of a rapid lineage diversification early in the clade's history, nor of any shifts in diversification rates induced by glacial cycles. This suggests that a high turnover rate on the repeatedly scoured Antarctic shelf could have masked potential signals of diversification bursts.
南极大陆架的海洋生物多样性受到该地区气候和冰川历史的极大影响。极端的温度变化导致一些谱系灭绝，而其他谱系则适应并繁荣起来。端足类动物Epimeria属就是后者的一个例子，在南极地区尤其多样化。通过基于线粒体（COI）和核基因（28S和H3）标记重建一个时间校准的系统发育树，并纳入来自所有海洋的Epimeria物种，本研究为南极Epimeria的进化提供了一个时间和地理框架。贝叶斯推断不支持该属的单系性，因为南极和非南极的Epimeria形成了两个不同的、得到充分支持的分支，南极Epimeria是两个长足类物种的姐妹分支。南极Epimeria的单系性表明，这个分支自起源以来一直在隔离中进化。虽然这个起源的确切时间仍不清楚，但据推断，南极谱系起源于冈瓦纳晚期的一个祖先，因此在南极洲与冈瓦纳大陆的其他部分分离后，并没有殖民南极地区。该分支的初始多样化发生在38.04Ma（95% HPD [48.46Ma；28.36Ma]）的一个冷却环境中。对冷水的适应，以及不耐寒类群的灭绝和由此产生的生态机会，可能导致了Epimeria在南极大陆架上的成功多样化。然而，既没有证据表明该分支历史早期有快速的谱系多样化，也没有证据表明冰川周期导致了多样化速率的任何变化。这表明，在反复被冲刷的南极大陆架上的高周转率可能掩盖了多样化爆发的潜在信号。
