Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
PLoS One. 2013 Aug 16;8(8):e71069. doi: 10.1371/journal.pone.0071069. eCollection 2013.
The process of ecological speciation drives the evolution of locally adapted and reproductively isolated populations in response to divergent natural selection. In Southern Mexico, several lineages of the freshwater fish species of the genus Poecilia have independently colonized toxic, hydrogen sulfide-rich springs. Even though ecological speciation processes are increasingly well understood in this system, aligning the taxonomy of these fish with evolutionary processes has lagged behind. While some sulfide spring populations are classified as ecotypes of Poecilia mexicana, others, like P. sulphuraria, have been described as highly endemic species. Our study particularly focused on elucidating the taxonomy of the long described sulfide spring endemic, Poecilia thermalis Steindachner 1863, and investigates if similar evolutionary patterns of phenotypic trait divergence and reproductive isolation are present as observed in other sulfidic species of Poecilia. We applied a geometric morphometric approach to assess body shape similarity to other sulfidic and non-sulfidic fish of the genus Poecilia. We also conducted phylogenetic and population genetic analyses to establish the phylogenetic relationships of P. thermalis and used a population genetic approach to determine levels of gene flow among Poecilia from sulfidic and non-sulfidic sites. Our results indicate that P. thermalis' body shape has evolved in convergence with other sulfide spring populations in the genus. Phylogenetic analyses placed P. thermalis as most closely related to one population of P. sulphuraria, and population genetic analyses demonstrated that P. thermalis is genetically isolated from both P. mexicana ecotypes and P. sulphuraria. Based on these findings, we make taxonomic recommendations for P. thermalis. Overall, our study verifies the role of hydrogen sulfide as a main factor shaping convergent, phenotypic evolution and the emergence of reproductive isolation between Poecilia populations residing in adjacent sulfidic and non-sulfidic environments.
生态物种形成过程驱动了局部适应和生殖隔离种群的进化，以应对不同的自然选择。在墨西哥南部，几种丽鱼科淡水鱼类的谱系独立地殖民到了毒性、富含硫化氢的泉水里。尽管在这个系统中，生态物种形成过程已经越来越被理解，但这些鱼类的分类与进化过程之间仍然存在差距。虽然一些硫化物泉水种群被归类为墨西哥丽鱼（Poecilia mexicana）的生态型，但其他种群，如硫磺丽鱼（Poecilia sulphuraria），则被描述为高度特有物种。我们的研究特别关注阐明长期以来被描述的硫化物泉水特有种——热力丽鱼（Poecilia thermalis Steindachner 1863）的分类学，并调查是否存在与其他丽鱼科硫化物物种中观察到的类似表型性状分歧和生殖隔离的进化模式。我们应用了几何形态测量方法来评估与其他硫化物和非硫化物丽鱼属鱼类的体型相似性。我们还进行了系统发育和种群遗传分析，以确定热力丽鱼的系统发育关系，并使用种群遗传方法来确定来自硫化物和非硫化物地点的丽鱼属之间的基因流动水平。我们的结果表明，热力丽鱼的体型已经与属中的其他硫化物泉水种群趋同进化。系统发育分析将热力丽鱼与硫磺丽鱼的一个种群关系最为密切，种群遗传分析表明热力丽鱼在遗传上与墨西哥丽鱼的两个生态型和硫磺丽鱼都相互隔离。基于这些发现，我们对热力丽鱼提出了分类学建议。总的来说，我们的研究验证了硫化氢作为塑造趋同表型进化和相邻硫化物和非硫化物环境中丽鱼种群之间生殖隔离出现的主要因素的作用。
