Data from: The linking of plate tectonics and evolutionary divergences

It is exciting to be living at a time when the big questions in biology can be investigated using modern genetics and computing. Bauzà-Ribot et al. take on one of the fundamental drivers of biodiversity, the effect of continental drift in the formation of the world’s biota, employing next-generation sequencing of whole mitochondrial genomes and modern Bayesian relaxed molecular clock analysis. Bauzà-Ribot et al. conclude that vicariance via plate tectonics best explains the genetic divergence between subterranean metacrangonyctid amphipods currently found on islands separated by the Atlantic Ocean. This finding is a big deal in biogeography, and science generally, as many other presumed biotic tectonic divergences have been explained as probably due to more recent transoceanic dispersal events. However, molecular clocks can be problematic and we have identified three issues with the analyses of Bauzà-Ribot et al. that cast serious doubt on their results and conclusions. When we reanalyzed their mitochondrial data and attempted to account for problems with calibration [5,6], modeling rates across branches and substitution saturation, we inferred a much younger date for their key node. This implies either a later trans-Atlantic dispersal of these crustaceans, or more likely a series of later invasions of freshwaters from a common marine ancestor, but either way probably not ancient tectonic plate movements.

我们正处于一个可借助现代遗传学与计算技术探究生物学重大问题的时代，这无疑令人振奋。Bauzà-Ribot等人聚焦生物多样性的核心驱动因素之一——大陆漂移对全球生物区系形成的影响，采用全线粒体基因组下一代测序（next-generation sequencing）与贝叶斯宽松分子钟分析（Bayesian relaxed molecular clock analysis）开展研究。
Bauzà-Ribot等人得出结论：板块构造（plate tectonics）引发的地理分替（vicariance）最能解释当前分布于大西洋分隔岛屿的地下异钩虾科端足类之间的遗传分化。这一发现在生物地理学乃至整个科学界都具有重要意义，因为此前诸多被认为由生物类群构造分化导致的案例，现已被证实大概率源于更近时期的跨洋扩散（transoceanic dispersal）事件。
然而，分子钟分析本身存在固有局限，我们在Bauzà-Ribot等人的研究中发现了三处会严重质疑其结果与结论的分析缺陷。当我们重新分析其线粒体数据，并尝试解决校准偏差、分支间速率建模以及替换饱和（substitution saturation）三类问题后，推断出其关键节点的分化时间要年轻得多。这一结果意味着，要么这些甲壳动物是在更晚近的时间跨大西洋扩散而来，更有可能的是它们由共同的海洋祖先多次后续入侵淡水生境，但无论哪种情况，其分化都不太可能源自古老的板块运动。