Department of Biology, University of Louisiana at Lafayette, Lafayette, LA, United States of America.
Museu de Zoologia da Universidade de São Paulo, São Paulo, São Paulo, Brazil.
PLoS One. 2019 Nov 7;14(11):e0224599. doi: 10.1371/journal.pone.0224599. eCollection 2019.
The diversity of gymnotid electric fishes has been intensely studied over the past 25 years, with 35 species named since 1994, compared to 11 species in the previous 236 years. Substantial effort has also been applied in recent years to documenting gymnotid interrelationships, with seven systematic studies published using morphological and molecular datasets. Nevertheless, until now, all gymnotids have been assigned to one of just two supraspecific taxa, the subfamily Electrophorinae with one genus Electrophorus and three valid species and the subfamily Gymnotine also with one genus Gymnotus and 43 valid species. This simple classification has obscured the substantial phenotypic and lineage diversity within the subfamily Gymnotine and hampered ecological and evolutionary studies of gymnotid biology. Here we present the most well-resolved and taxon-complete phylogeny of the Gymnotidae to date, including materials from all but one of the valid species. This phylogeny was constructed using a five-gene molecular dataset and a 115-character morphological dataset, enabling the inclusion of several species for which molecular data are still lacking. This phylogeny was time-calibrated using biogeographical priors in the absence of a fossil record. The tree topology is similar to those of previous studies, recovering all the major clades previously recognized with informal names. We propose a new gymnotid classification including two subfamilies (Electrophorinae and Gymnotinae) and six subgenera within the genus Gymnotus. Each subgenus exhibits a distinctive biogeographic distribution, within which most species have allopatric distributions and the subgenera are diverged from one another by an estimated 5-35 million years. We further provide robust taxonomic diagnoses, descriptions and identification keys to all gymnotid subgenera and all but four species. This new taxonomy more equitably partitions species diversity among supra-specific taxa, employing the previously vacant subgenus and subfamily ranks. This new taxonomy renders known gymnotid diversity more accessible to study by highlighting the deep divergences (chronological, geographical, genetic and morphological) among its several clades.
过去 25 年来，人们对电鳗目鱼类的多样性进行了深入研究，自 1994 年以来已命名了 35 个物种，而在此前的 236 年中只命名了 11 个物种。近年来，人们还在努力记录电鳗目鱼类的相互关系，使用形态学和分子数据集发表了 7 项系统研究。然而，直到现在，所有电鳗目鱼类都被归入仅有两个超种分类单元之一，即一科 Electrophorinae，包括一个 Electrophorus 属和 3 个有效种，和一科 Gymnotine，包括一个 Gymnotus 属和 43 个有效种。这种简单的分类方法掩盖了 Gymnotine 科内部的大量表型和谱系多样性，并阻碍了电鳗目生物学的生态和进化研究。在这里，我们展示了迄今为止最完善和分类最完整的电鳗目系统发育关系，包括所有有效种的除一种以外的材料。该系统发育关系是使用五基因分子数据集和 115 个字符形态数据集构建的，能够包括几个仍缺乏分子数据的物种。该系统发育关系使用生物地理先验进行了时间校准，因为没有化石记录。该树拓扑结构与之前的研究相似，恢复了以前用非正式名称识别的所有主要分支。我们提出了一个新的电鳗目分类，包括两个亚科（Electrophorinae 和 Gymnotinae）和 Gymnotus 属内的 6 个亚属。每个亚属都有独特的生物地理分布，其中大多数物种都有地理上的分布，并且亚属之间的分化距离估计为 5-3500 万年。我们进一步提供了所有电鳗目亚属和除 4 个种以外的所有种的可靠分类学诊断、描述和鉴定钥匙。这种新的分类法更公平地将物种多样性分配到超种分类单元中，采用了以前空缺的亚属和亚科等级。这种新的分类法使已知的电鳗目多样性更容易通过突出其几个分支之间的深刻分歧（时间上、地理上、遗传上和形态上）来进行研究。
