Evolutionary Ecology Laboratories, Department of Biology, Brigham Young University, 401 WIDB, Provo, UT 84602, USA.
Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Panama.
Mol Phylogenet Evol. 2015 Aug;89:104-14. doi: 10.1016/j.ympev.2015.04.013. Epub 2015 Apr 24.
The livebearing fish genus Brachyrhaphis (Poeciliidae) has become an increasingly important model in evolution and ecology research, yet the phylogeny of this group is not well understood, nor has it been examined thoroughly using modern phylogenetic methods. Here, we present the first comprehensive phylogenetic analysis of Brachyrhaphis by using four molecular markers (3mtDNA, 1nucDNA) to infer relationships among species in this genus. We tested the validity of this genus as a monophyletic group using extensive outgroup sampling based on recent phylogenetic hypotheses of Poeciliidae. We also tested the validity of recently described species of Brachyrhaphis that are part of the B. episcopi complex in Panama. Finally, we examined the impact of historical events on diversification of Brachyrhaphis, and made predictions regarding the role of different ecological environments on evolutionary diversification where known historical events apparently fail to explain speciation. Based on our results, we reject the monophyly of Brachyrhaphis, and question the validity of two recently described species (B. hessfeldi and B. roswithae). Historical biogeography of Brachyrhaphis generally agrees with patterns found in other freshwater taxa in Lower Central America, which show that geological barriers frequently predict speciation. Specifically, we find evidence in support of an 'island' model of Lower Central American formation, which posits that the nascent isthmus was partitioned by several marine connections before linking North and South America. In some cases where historic events (e.g., vicariance) fail to explain allopatric species breaks in Brachyrhaphis, ecological processes (e.g., divergent predation environments) offer additional insight into our understanding of phylogenetic diversification in this group.
胎生鱼类 Brachyrhaphis 属（胎生鱂科）在进化和生态学研究中已成为越来越重要的模式生物，但该属的系统发育关系尚未得到很好的理解，也未使用现代系统发育方法进行彻底研究。在这里，我们使用四个分子标记（3mtDNA、1nucDNA）对 Brachyrhaphis 属进行了首次全面的系统发育分析，以推断该属内物种之间的关系。我们基于胎生鱂科最近的系统发育假说，通过广泛的外群采样来检验该属作为一个单系群的有效性。我们还检验了最近描述的巴拿马 Brachyrhaphis episcopi 复合体中部分物种的有效性。最后，我们检验了历史事件对 Brachyrhaphis 多样化的影响，并就不同生态环境对进化多样化的作用做出了预测，因为已知的历史事件显然无法解释物种形成。基于我们的结果，我们否定了 Brachyrhaphis 的单系性，并对最近描述的两个物种（B. hessfeldi 和 B. roswithae）的有效性提出质疑。Brachyrhaphis 的历史生物地理学与中美洲低地的其他淡水分类群的模式基本一致，这表明地质障碍经常预示着物种形成。具体来说，我们有证据支持中美洲低地形成的“岛屿”模式，该模式认为新生地峡在连接北美和南美之前曾被几个海洋连接所分隔。在某些情况下，历史事件（例如隔离）无法解释 Brachyrhaphis 中同域物种的断裂时，生态过程（例如，不同的捕食环境）为我们理解该组的系统发育多样化提供了更多的见解。
