Data from: Appearance of an early closure of the Isthmus of Panama is the product of biased inclusion of data in the metaanalysis

In their PNAS article “Biological evidence supports an early and complex emergence of the Isthmus of Panama,” Bacon et al. (1 - http://dx.doi.org/10.1073/pnas.1423853112) use data from molecular comparisons of terrestrial and marine organisms taken from the literature to estimate dates of rate shifts in migration. One of their conclusions is that “events separating marine organisms in the Atlantic and Pacific oceans [occurred] at ca. 23 and 7 Ma” (1). The authors base this conclusion on two kinds of molecular dating: (i) 31 dates from phylogenies with evolutionary rates calibrated from fossils at one or more nodes, and (ii) 52 dates from mitochondrial divergence between sister species on either side of the Isthmus taken from the review by Lessios (2) (note: complete data are available from the Dryad Digital Repository at http://dx.doi.org/10.5061/dryad.6m653). For the latter, divergence was converted to time by assuming a mitochondrial DNA divergence rate of 2% per million years. Unfortunately, Bacon et al.’s metaanalysis of separations of marine organisms contains unexplained omissions of data and mistakes.

Bacon等人在其发表于《美国国家科学院院刊》（Proceedings of the National Academy of Sciences, PNAS）的文章《生物学证据支持巴拿马地峡早期且复杂的形成》（参考文献1，链接：http://dx.doi.org/10.1073/pnas.1423853112）中，利用文献收录的陆生与海洋生物分子比对数据，估算了生物迁徙速率变化的发生时间。其其中一项结论为："大西洋与太平洋海洋生物的隔离事件分别发生于约23 Ma和7 Ma"（1）。该结论基于两类分子定年数据：(i) 基于一个或多个节点的化石校准进化速率的系统发育树得到的31组定年结果；(ii) 源自Lessios（2）综述的、巴拿马地峡两侧姊妹种间的线粒体分化数据，共计52组。（注：完整数据集可从Dryad数字知识库（Dryad Digital Repository）获取，链接：http://dx.doi.org/10.5061/dryad.6m653）。针对第二类数据，研究人员通过假定线粒体DNA（mitochondrial DNA）每百万年的分化速率为2%，将分化程度转换为分化时间。但遗憾的是，Bacon等人针对海洋生物隔离事件的荟萃分析存在未予解释的数据遗漏与错误。