Eocene habitat shift from saline to freshwater promoted Tethyan amphipod diversification
Eocene habitat shift from saline to freshwater promoted Tethyan amphipod diversification
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始新世栖息地从盐水到淡水的转变促进了特提斯片脚类动物的多样化
DOI：
10.1073/pnas.1104636108
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发表时间：
2011-08-30
影响因子：
11.1
通讯作者：
Li, Shuqiang
中科院分区：
文献类型：
--
作者：
Hou, Zhonge;Sket, Boris;Li, Shuqiang
目前的理论预测，向新栖息地的转变将提高多样化的速度，而随着谱系进化成多个物种，激烈的竞争将降低多样化的速度。我们使用 Gammarus 属的全北片脚类动物来检验这一假设。我们对代表 115 个伽马属物种的 289 个样本的 4 个基因（5,088 bp）进行了测序。系统发育分析表明，Gammarus起源于特提斯地区，在古新世有盐水祖先，后来在中始新世定居于淡水栖息地。祖先范围重建和多样化模式分析结合古地质和古气候证据表明，栖息地从盐水到淡水的转变导致多样化率增加。由于特提斯海和大西洋之间的屏障很少，伽马鲁斯的盐系谱系于 5500 万年前（Ma）分散到大西洋两岸，并在整个进化史上以恒定的多样化率[每百万年 0.04 个物种（sp/My）]实现多样化。然而，直到中新世中期，淡水伽马鱼经历了一个快速多样化阶段（0.11 sp/My），并且谱系通过可能由特提斯和陆地变化驱动的替代过程在欧亚大陆相继多样化。特别是淡水Gammarus lacustris和Gammarus balcanicus谱系具有相对较高的多样化转变，对应于中新世时期副特提斯海的退缩和欧亚大陆的大陆化。随后（14 Ma），淡水Gammarus 的多样化率下降至0.05，并再次下降至0.01 sp/My。钩虾属提供了一个极好的水生案例，支持生态机会促进多样化的假设。
Current theory predicts that a shift to a new habitat would increase the rate of diversification, while as lineages evolve into multiple species, intensified competition would decrease the rate of diversification. We used Holarctic amphipods of the genus Gammarus to test this hypothesis. We sequenced four genes (5,088 bp) for 289 samples representing 115 Gammarus species. A phylogenetic analysis showed that Gammarus originated from the Tethyan region with a saline ancestry in the Paleocene, and later colonized the freshwater habitat in the Middle Eocene. Ancestral range reconstruction and diversification mode analysis combined with paleogeological and paleoclimatic evidence suggested that the habitat shift from saline to freshwater led to an increased diversification rate. The saline lineage of Gammarus dispersed to both sides of the Atlantic at 55 million years ago (Ma), because of the few barriers between the Tethys and the Atlantic, and diversified throughout its evolutionary history with a constant diversification rate [0.04 species per million years (sp/My)]. The freshwater Gammarus, however, underwent a rapid diversification phase (0.11 sp/My) until the Middle Miocene, and lineages successively diversified across Eurasia via vicariance process likely driven by changes of the Tethys and landmass. In particular, the freshwater Gammarus lacustris and Gammarus balcanicus lineages had a relatively high diversification shift, corresponding to the regression of the Paratethys Sea and the continentalization of Eurasian lands during the Miocene period. Subsequently (14 Ma), the diversification rate of the freshwater Gammarus decreased to 0.05 and again to 0.01 sp/My. The genus Gammarus provides an excellent aquatic case supporting the hypothesis that ecological opportunities promote diversification.