Department of Evolution and Ecology, Center for Population Biology, University of California, Davis, Davis, California, 95616.
Evolution. 2020 May;74(5):950-961. doi: 10.1111/evo.13971. Epub 2020 Apr 23.
Functional decoupling of oral and pharyngeal jaws is widely considered to have expanded the ecological repertoire of cichlid fishes. But, the degree to which the evolution of these jaw systems is decoupled and whether decoupling has impacted trophic diversification remains unknown. Focusing on the large Neotropical radiation of cichlids, we ask whether oral and pharyngeal jaw evolution is correlated and how their evolutionary rates respond to feeding ecology. In support of decoupling, we find relaxed evolutionary integration between the two jaw systems, resulting in novel trait combinations that potentially facilitate feeding mode diversification. These outcomes are made possible by escaping the mechanical trade-off between force transmission and mobility, which characterizes a single jaw system that functions in isolation. In spite of the structural independence of the two jaw systems, results using a Bayesian, state-dependent, relaxed-clock model of multivariate Brownian motion indicate strongly aligned evolutionary responses to feeding ecology. So, although decoupling of prey capture and processing functions released constraints on jaw evolution and promoted trophic diversity in cichlids, the natural diversity of consumed prey has also induced a moderate degree of evolutionary integration between the jaw systems, reminiscent of the original mechanical trade-off between force and mobility.
口腔和咽颚的功能分离被广泛认为扩展了慈鲷鱼类的生态位。但是，这些颚系统的分离程度以及分离是否影响了营养多样性仍然未知。本研究聚焦于大型新热带慈鲷辐射，我们探讨了口腔和咽颚的进化是否相关，以及它们的进化速率如何响应摄食生态。支持分离的结果发现，两个颚系统之间的进化整合程度降低，导致潜在的新的特征组合，从而促进了摄食模式的多样化。这些结果是通过摆脱单个独立运作的颚系统在力传递和活动性之间的机械权衡来实现的。尽管两个颚系统在结构上是独立的，但使用基于贝叶斯的、状态依赖的多变量布朗运动松弛时钟模型的结果表明，对摄食生态的进化响应是高度一致的。因此，尽管捕食和处理功能的分离释放了对颚进化的限制，并促进了慈鲷的营养多样性，但被消耗猎物的自然多样性也在一定程度上导致了颚系统之间的进化整合，这让人联想到力和活动性之间最初的机械权衡。
