Department of Zoology, University of British Columbia, Vancouver, Canada.
Am Nat. 2010 Sep;176(3):335-56. doi: 10.1086/655221.
Natural selection arising from resource competition and environmental heterogeneity can drive adaptive radiation. Ecological opportunity facilitates this process, resulting in rapid divergence of ecological traits in many celebrated radiations. In other cases, sexual selection is thought to fuel divergence in mating signals ahead of ecological divergence. Comparing divergence rates between naturally and sexually selected traits can offer insights into processes underlying species radiations, but to date such comparisons have been largely qualitative. Here, we quantitatively compare divergence rates for four traits in African mormyrid fishes, which use an electrical communication system with few extrinsic constraints on divergence. We demonstrate rapid signal evolution in the Paramormyrops species flock compared to divergence in morphology, size, and trophic ecology. This disparity in the tempo of trait evolution suggests that sexual selection is an important early driver of species radiation in these mormyrids. We also found slight divergence in ecological traits among closely related species, consistent with a supporting role for natural selection in Paramormyrops diversification. Our results highlight the potential for sexual selection to drive explosive signal divergence when innovations in communication open new opportunities in signal space, suggesting that opportunity can catalyze species radiations through sexual selection, as well as natural selection.
自然选择源于资源竞争和环境异质性，能够驱动适应性辐射。生态机会促进了这一过程，导致许多著名辐射中生态特征的快速分歧。在其他情况下，性选择被认为是在生态分歧之前推动交配信号的分歧。比较自然选择和性选择特征的分歧率可以深入了解物种辐射背后的过程，但迄今为止，这些比较主要是定性的。在这里，我们定量比较了非洲电鳗鱼类中四个特征的分歧率，这些鱼类使用一种电通讯系统，其分歧受到的外在限制很少。与形态、大小和营养生态的分歧相比，我们在 Paramormyrops 种群中发现了信号的快速进化。这种特征进化速度的差异表明，性选择是这些电鳗鱼类物种辐射的一个重要早期驱动因素。我们还发现，在密切相关的物种之间，生态特征存在轻微分歧，这与自然选择在 Paramormyrops 多样化中的支持作用一致。我们的研究结果强调了在通讯创新开辟信号空间新机会时，性选择驱动爆炸性信号分歧的潜力，这表明机会可以通过性选择以及自然选择来加速物种辐射。
