Under an ecological speciation scenario, the radiation of African weakly electric fish (genus Campylomormyrus) is caused by an adaptation to different food sources, associated with diversification of the electric organ discharge (EOD). This study experimentally investigates a phenotype–environment correlation to further support this scenario. Our behavioural experiments showed that three sympatric Campylomormyrus species with significantly divergent snout morphology differentially react to variation in substrate structure. While the short snout species (C. tamandua) exhibits preference to sandy substrate, the long snout species (C. rhynchophorus) significantly prefers a stone substrate for feeding. A third species with intermediate snout size (C. compressirostris) does not exhibit any substrate preference. This preference is matched with the observation that long-snouted specimens probe deeper into the stone substrate, presumably enabling them to reach prey more distant to the substrate surface. These findings suggest that the diverse feeding apparatus in the genus Campylomormyrus may have evolved in adaptation to specific microhabitats, i.e., substrate structures where these fish forage. Whether the parallel divergence in EOD is functionally related to this adaptation or solely serves as a prezygotic isolation mechanism remains to be elucidated.

中文翻译：

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非洲弱电鱼（Campylomormyrus）的形态分化与底物偏好有关

在生态物种形成情景下，非洲弱电鱼（Campylomormyrus）的辐射是由对不同食物来源的适应引起的，与电器官放电（EOD）的多样化有关。这项研究通过实验研究了表型-环境的相关性，以进一步支持这种情况。我们的行为实验表明，具有显着不同的鼻子形态的三种同域 Campylomormyrus 物种对基质结构的变化有不同的反应。虽然短吻物种 (C. tamandua) 表现出对沙质基质的偏好，但长吻物种 (C. rhynchophorus) 明显更喜欢石质基质进行觅食。具有中等鼻子大小的第三种物种（C. compressirostris）没有表现出任何底物偏好。这种偏好与观察结果相匹配，即长吻标本深入石头基底，可能使它们能够到达距离基底表面更远的猎物。这些发现表明，Campylomormyrus 属的多种摄食装置可能已经进化为适应特定的微生境，即这些鱼觅食的基质结构。EOD 的平行发散是否在功能上与这种适应有关，还是仅作为一种前合子隔离机制仍有待阐明。这些鱼觅食的基质结构。EOD 的平行发散是否在功能上与这种适应有关，还是仅作为一种前合子隔离机制仍有待阐明。这些鱼觅食的基质结构。EOD 的平行发散是否在功能上与这种适应有关，还是仅作为一种前合子隔离机制仍有待阐明。