Alves-Gomes J A, Ortí G, Haygood M, Heiligenberg W, Meyer A
Instituto Nacional de Pesquisas da Amazônia.
Mol Biol Evol. 1995 Mar;12(2):298-318. doi: 10.1093/oxfordjournals.molbev.a040204.
The order Gymnotiformes (South American electric fishes) is a fascinating assemblage of freshwater fishes that share the unusual ability to produce and sense electric fields used for electrolocation and social communication. In the last few decades, the electrogenic and electrosensory systems (EES) of these fish have served as an excellent model to study motor and sensory physiology in vertebrates. In an attempt to the evolution of characters associated with the EES in the group, we applied maximum-parsimony (MP), minimum-evolution (ME), and maximum-likelihood (ML) methods to analyze 302 aligned bases of the mitochondrial 12S rRNA and 416 bases of the mitochondrial 16S rRNA of 19 gymnotiform genera representing all six recognized families. Six catfish genera (order Siluriformes) were also sequenced and used as outgroups. The phylogenetic hypothesis resultant from molecular data analysis differs in some respects from previous hypotheses based on morphological studies. Our results were most informative within the family level, as we were unable to elucidate the relationships among deeper branches in this order with sufficient confidence by using molecular data alone. The phylogenetic information of both mitochondrial DNA segments appears to be affected by functional constraints, and the resultant topologies were sensitive to different weighting schemes and the algorithm used. Nonetheless, we found unanimous support for the following phylogenetic relationships: (1) the family Sternopygidae is an unnatural group, and Sternopygus is the sole representative of a unique lineage within the order; (2) the family Hypopomidae is not monophyletic; and (3) the order Gymnotiformes is composed of at least six natural clades: Sternopygus, family Apteronotidae, a new clade consisting of the remaining sternopygids, families Hypopomidae + Rhamphicthyidae, family Electrophoridae, and family Gymnotidae. By combining molecular, morphological, and physiological information, we propose a new hypothesis for the phylogeny of this group and suggest a new family Eigenmanniidae n. (order Gymnotiformes).
裸背电鳗目（南美电鱼）是一类迷人的淡水鱼，它们具有一项独特的能力，即能够产生并感知用于电定位和社交交流的电场。在过去几十年里，这些鱼类的发电和电感应系统（EES）一直是研究脊椎动物运动和感觉生理学的优秀模型。为了探究该类群中与EES相关特征的进化，我们应用最大简约法（MP）、最小进化法（ME）和最大似然法（ML），对代表所有六个已确认科的19个裸背电鳗目属的线粒体12S rRNA的302个比对碱基和线粒体16S rRNA的416个碱基进行了分析。还对六个鲶鱼属（鲶形目）进行了测序，并用作外类群。分子数据分析得出的系统发育假说在某些方面与先前基于形态学研究的假说不同。我们的结果在科级水平上提供了最多的信息，因为仅通过分子数据，我们无法足够自信地阐明该目更深分支之间的关系。两个线粒体DNA片段的系统发育信息似乎都受到功能限制的影响，所得拓扑结构对不同的加权方案和使用的算法很敏感。尽管如此，我们发现以下系统发育关系得到了一致支持：（1）裸背电鳗科是一个非自然类群，裸背电鳗属是该目中一个独特谱系的唯一代表；（2）低臀电鳗科不是单系的；（3）裸背电鳗目至少由六个自然分支组成：裸背电鳗属、无背鳍电鳗科、一个由其余裸背电鳗科鱼类组成的新分支、低臀电鳗科+尖吻电鳗科、电鳗科和裸背鳗科。通过结合分子、形态和生理信息，我们提出了该类群系统发育的新假说，并建议设立一个新科 Eigenmanniidae n.（裸背电鳗目）。
