Trade-offs are thought to bias evolution and are core features of many anatomical systems. Therefore, trade-offs may have far-reaching macroevolutionary consequences, including patterns of morphological, functional, and ecological diversity. Jaws, like many complex anatomical systems, are comprised of elements involved in biomechanical trade-offs. We test the impact of a core mechanical trade-off, transmission of velocity versus force (i.e., mechanical advantage), on rates of jaw evolution in Neotropical cichlids. Across 130 species representing a wide array of feeding ecologies, we find that the velocity-force trade-off impacts evolution of the surrounding jaw system. Specifically, rates of jaw evolution are faster at functional extremes than in more functionally intermediate or unspecialized jaws. Yet, surprisingly, the effect on jaw evolution is uneven across the extremes of the velocity-force continuum. Rates of jaw evolution are 4 to 10-fold faster in velocity-modified jaws, whereas force-modified jaws are 7 to 18-fold faster, compared to unspecialized jaws, depending on the extent of specialization. Further, we find that a more extreme mechanical trade-off resulted in faster rates of jaw evolution. The velocity-force trade-off reflects a gradient from specialization on capture-intensive (e.g., evasive or buried) to processing-intensive prey (e.g., attached or shelled), respectively. The velocity extreme of the trade-off is characterized by large magnitudes of trait change leading to functionally divergent specialists and ecological stasis. By contrast, the force extreme of the trade-off is characterized by enhanced ecological lability made possible by phenotypes more readily co-opted for different feeding ecologies. This asymmetry of macroevolutionary outcomes along each extreme is likely the result of an enhanced utility of the pharyngeal jaw system as force-modified oral jaws are adapted for prey that require intensive processing (e.g., algae, detritus, and molluscs). The velocity-force trade-off, a fundamental feature of many anatomical systems, promotes rapid phenotypic evolution of the surrounding jaw system in a canonical continental adaptive radiation. Considering that the velocity-force trade-off is an inherent feature of all jaw systems that involve a lower element that rotates at a joint, spanning the vast majority of vertebrates, our results may be widely applicable across the tree of life. [adaptive radiation; constraint; decoupling; jaws; macroevolution; specialization]

中文翻译：

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功能权衡不对称地促进表型进化

权衡被认为会使进化产生偏差，并且是许多解剖系统的核心特征。因此，权衡取舍可能会产生深远的宏观进化后果，包括形态、功能和生态多样性的模式。与许多复杂的解剖系统一样，颌骨由涉及生物力学权衡的元素组成。我们测试核心机械权衡、速度与力的传输（即机械优势）对新热带慈鲷颌骨进化速率的影响。在代表各种摄食生态的 130 个物种中，我们发现速度-力权衡影响周围颌系统的进化。具体来说，在功能极端的情况下，颌骨的进化速度比在功能更为中等或非专业的颌骨中要快。然而，令人惊讶的是，在速度-力连续体的极端情况下，对颌骨进化的影响是不均衡的。与非专业化的颌骨相比，速度修饰的颌骨的颌骨进化速度快 4 到 10 倍，而力修饰的颌骨则快 7 到 18 倍，具体取决于专业化程度。此外，我们发现更极端的机械权衡导致更快的下颌进化速度。速度力权衡反映了从捕获密集型（例如，回避或掩埋）专业化到加工密集型猎物（例如，附着或带壳）的梯度。权衡的速度极端的特点是大量的特征变化导致功能上不同的专家和生态停滞。相比之下，权衡的极端力量的特点是生态不稳定性增强，表型更容易适应不同的饲养生态。每个极端的宏观进化结果的这种不对称性可能是咽颌系统效用增强的结果，因为力修饰的口颌适用于需要密集加工的猎物（例如藻类、碎屑和软体动物）。速度力权衡是许多解剖系统的基本特征，它促进了典型大陆适应性辐射中周围颌系统的快速表型进化。考虑到速度-力权衡是所有颌骨系统的固有特征，涉及在关节处旋转的下部元件，跨越绝大多数脊椎动物，我们的结果可能广泛适用于整个生命之树。[自适应辐射；约束; 解耦；颚; 宏观进化；专业化]