The Atherinopsidae is the second largest group of freshwater fishes occupying central Mexico and is one of biological, cultural, and economic importance. The “humboldtianum” clade (Genus Chirostoma) is a “species flock” of nine described species that inhabit lacustrine ecosystems in central Mexico. The high morphological polymorphism within the group makes species identification difficult and thereby limits the development of research and management projects focusing on this group. In this study, we used phylogeographic and coalescent-based methods to understand the evolution of genetic variation among these species. The results revealed taxonomic inaccuracies and genetic admixture among species. Genetic variation was structured geographically, rather than taxonomically, and five closely related genetic groups were recovered. Two evolutionary pathways were found. First, a novel geographical arrangement of haplotypes was recovered that gave rise to the five recently (Pleistocene, < 1 Myr) derived genetic groups. The second pathway showed a recent intra-lacustrine genetic differentiation that could be associated with sympatric or ecological speciation. The current classification of the group is revised and includes a reduction in the number of valid species in the “humboldtianum” clade. Moreover, this study provides new insight into the biogeography and evolutionary history of this important group of fishes.

中文翻译：

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墨西哥中部濒临灭绝的银边“humboldtianum”进化枝（双鱼座：Atherinopsidae）的系统地理学模式和物种划分：了解它们的进化历史

Atherinopsidae 是占据墨西哥中部的第二大淡水鱼类群，具有重要的生物学、文化和经济意义。“humboldtianum”进化枝（Chirostoma 属）是居住在墨西哥中部湖泊生态系统中的九种已描述物种的“物种群”。该群体内的高形态多态性使得物种鉴定变得困难，从而限制了以该群体为重点的研究和管理项目的发展。在这项研究中，我们使用系统地理学和基于聚结的方法来了解这些物种之间遗传变异的进化。结果揭示了物种之间的分类不准确和遗传混合。遗传变异是按地理而不是分类学来构建的，并且发现了五个密切相关的遗传组。发现了两种进化途径。首先，发现了一种新的单倍型地理排列，它产生了五个最近（更新世，< 1 Myr）衍生的遗传组。第二种途径显示了最近的湖内遗传分化，这可能与同域或生态物种形成有关。该组的当前分类进行了修订，包括减少了“humboldtianum”进化枝中有效物种的数量。此外，这项研究为这一重要鱼类的生物地理学和进化史提供了新的见解。第二种途径显示了最近的湖内遗传分化，这可能与同域或生态物种形成有关。该组的当前分类进行了修订，包括减少了“humboldtianum”进化枝中有效物种的数量。此外，这项研究为这一重要鱼类的生物地理学和进化史提供了新的见解。第二种途径显示了最近的湖内遗传分化，这可能与同域或生态物种形成有关。该组的当前分类进行了修订，包括减少了“humboldtianum”进化枝中有效物种的数量。此外，这项研究为这一重要鱼类的生物地理学和进化史提供了新的见解。