Marine species formation along the rise of Central America: the anomuran crab Megalobrachium

The evolution of marine neotropical shallow water species is expected to have been greatly affected by physical events related to the emergence of the Central American Isthmus. The anomuran crab Megalobrachium, a strictly neotropical porcellanid genus, consists of four species in the West Atlantic (WA) and nine in the East Pacific (EP). Dispersal is limited to a relatively short planktonic phase, which lasts approximately two weeks. We obtained DNA sequences of three mitochondrial and two nuclear genes of all but one species of Megalobrachium to construct a time-calibrated phylogeny of the genus and its historical phylogeography, based on the reconstruction of ancestral areas. The topology of the phylogenetic trees of Megalobrachium produced by Bayesian Inference (BI) and Maximum Likelihood (ML) were virtually congruent. The genus is monophyletic with respect to other porcellanids. Ancestral area reconstruction indicates that it arose in the eastern Pacific 18 million years ago and div...新热带区（Neotropical）海洋浅海物种的演化过程，被认为深受中美洲地峡（Central American Isthmus）形成相关物理事件的深刻影响。歪尾下目（Anomura）蟹类*Megalobrachium*属（隶属于瓷蟹科Porcellanidae，为严格的新热带区特有属），在西大西洋（West Atlantic，简称WA）分布有4个物种，东太平洋（East Pacific，简称EP）分布有9个物种。该类群的扩散仅局限于时长约两周的短暂浮游阶段。我们获取了除1个物种外所有*Megalobrachium*属物种的3个线粒体基因与2个核基因的DNA序列，基于祖先区域重建方法，构建该属的时间校准系统发育树及其历史生物地理学格局。贝叶斯推断（Bayesian Inference，简称BI）与最大似然法（Maximum Likelihood，简称ML）构建的*Megalobrachium*属系统发育树拓扑结构几乎完全一致。该属相较于其他瓷蟹科类群为单系群。祖先区域重建结果显示，该属起源于1800万年前的东太平洋，并于……