Smith Adam R, Proffitt Melissa R, Ho Winnie W, Mullaney Claire B, Maldonado-Ocampo Javier A, Lovejoy Nathan R, Alves-Gomes José A, Smith G Troy
Department of Biology, Indiana University, 1001 E. 3rd St, Bloomington, IN 47405, USA.
Department of Biology, Indiana University, 1001 E. 3rd St, Bloomington, IN 47405, USA.
J Physiol Paris. 2016 Oct;110(3 Pt B):302-313. doi: 10.1016/j.jphysparis.2016.10.002. Epub 2016 Oct 18.
The electric communication signals of weakly electric ghost knifefishes (Gymnotiformes: Apteronotidae) provide a valuable model system for understanding the evolution and physiology of behavior. Apteronotids produce continuous wave-type electric organ discharges (EODs) that are used for electrolocation and communication. The frequency and waveform of EODs, as well as the structure of transient EOD modulations (chirps), vary substantially across species. Understanding how these signals have evolved, however, has been hampered by the lack of a well-supported phylogeny for this family. We constructed a molecular phylogeny for the Apteronotidae by using sequence data from three genes (cytochrome c oxidase subunit 1, recombination activating gene 2, and cytochrome oxidase B) in 32 species representing 13 apteronotid genera. This phylogeny and an extensive database of apteronotid signals allowed us to examine signal evolution by using ancestral state reconstruction (ASR) and phylogenetic generalized least squares (PGLS) models. Our molecular phylogeny largely agrees with another recent sequence-based phylogeny and identified five robust apteronotid clades: (i) Sternarchorhamphus+Orthosternarchus, (ii) Adontosternarchus, (iii) Apteronotus+Parapteronotus, (iv) Sternarchorhynchus, and (v) a large clade including Porotergus, 'Apteronotus', Compsaraia, Sternarchogiton, Sternarchella, and Magosternarchus. We analyzed novel chirp recordings from two apteronotid species (Orthosternarchus tamandua and Sternarchorhynchus mormyrus), and combined data from these species with that from previously recorded species in our phylogenetic analyses. Some signal parameters in O. tamandua were plesiomorphic (e.g., low frequency EODs and chirps with little frequency modulation that nevertheless interrupt the EOD), suggesting that ultra-high frequency EODs and "big" chirps evolved after apteronotids diverged from other gymnotiforms. In contrast to previous studies, our PGLS analyses using the new phylogeny indicated the presence of phylogenetic signals in the relationships between some EOD and chirp parameters. The ASR demonstrated that most EOD and chirp parameters are evolutionarily labile and have often diversified even among closely related species.
弱电幽灵刀鱼（裸背电鳗目：无鳍电鳗科）的电通信信号为理解行为的进化和生理提供了一个有价值的模型系统。无鳍电鳗科鱼类产生连续波型的电器官放电（EODs），用于电定位和通信。EODs的频率和波形，以及瞬态EOD调制（啁啾声）的结构，在不同物种间有很大差异。然而，由于该科缺乏一个得到充分支持的系统发育树，了解这些信号是如何进化的受到了阻碍。我们通过使用来自32个物种的三个基因（细胞色素c氧化酶亚基1、重组激活基因2和细胞色素氧化酶B）的序列数据构建了无鳍电鳗科的分子系统发育树，这些物种代表了13个无鳍电鳗属。这个系统发育树和一个广泛的无鳍电鳗信号数据库使我们能够通过使用祖先状态重建（ASR）和系统发育广义最小二乘法（PGLS）模型来研究信号进化。我们的分子系统发育树在很大程度上与最近另一个基于序列的系统发育树一致，并确定了五个可靠的无鳍电鳗类群：（i） Sternarchorhamphus + Orthosternarchus，（ii） Adontosternarchus，（iii） Apteronotus + Parapteronotus，（iv） Sternarchorhynchus，以及（v） 一个包括Porotergus、“Apteronotus”、Compsaraia、Sternarchogiton、Sternarchella和Magosternarchus的大类群。我们分析了两种无鳍电鳗科鱼类（Orthosternarchus tamandua和Sternarchorhynchus mormyrus）的新型啁啾声记录，并将这些物种的数据与我们系统发育分析中先前记录物种的数据相结合。O. tamandua的一些信号参数是祖征（例如，低频EODs和频率调制很少但仍中断EOD的啁啾声），这表明超高频EODs和“大”啁啾声是在无鳍电鳗科与其他裸背电鳗目鱼类分化后进化而来的。与之前的研究不同，我们使用新系统发育树的PGLS分析表明，在一些EOD和啁啾声参数之间的关系中存在系统发育信号。ASR表明，大多数EOD和啁啾声参数在进化上是不稳定的，甚至在亲缘关系很近的物种之间也常常多样化。
