Arbour Jessica, Rumpp Faith, López-Fernández Hernán
Department of Biology, Middle Tennessee State University, Murfreesboro, Tennessee, USA.
Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, USA.
Anat Rec (Hoboken). 2024 Jan;307(1):81-96. doi: 10.1002/ar.25231. Epub 2023 Apr 27.
The diversification of functional traits may be limited by the intrinsic constraints of organismal form (i.e., constructional constraints), owing to the differential investment in different anatomical structures. In this study, we test whether overall organismal form impacts the evolution of shape and function in complex lever systems. We examined the relationship between four-bar shape and overall head shape in two four-bar linkage systems: the oral-jaw and hyoid-neurocranium systems in Neotropical cichlids. We also investigated the strength of form-function mapping in these four-bar linkages and the impact of constraining head shape on these correlations. We quantified the shape of the head and two four-bar linkages using geometric morphometrics and compared these with the kinematic transmission coefficient of each linkage system. The shapes of both linkages were strongly correlated with their mechanical properties, and head shape appears to constrain the shape of both four-bar linkages. Head shape induced greater integration between the two linkages, was associated with stronger form-function correlations and higher rates of evolution in biomechanically important features. Head shape constraints may also contribute to a weak but significant trade-off in linkage kinematics. Elongation of the head and body, in particular, appears to minimize the impact of this trade-off, possibly through maximizing anterior-posterior space availability. However, the strength of relationships between shape and function, and the impact of head shape differed between the two linkages, with the hyoid four-bar in general showing stronger form-function relationships despite being more independent from head shape constraints.
由于对不同解剖结构的投资差异，功能性状的多样化可能受到生物体形态的内在限制（即结构限制）。在本研究中，我们测试了整体生物体形态是否会影响复杂杠杆系统中形状和功能的进化。我们研究了新热带丽鱼科鱼类的两个四杆联动系统——口颌系统和舌骨-脑颅系统中四杆形状与整体头部形状之间的关系。我们还研究了这些四杆联动中形态-功能映射的强度以及限制头部形状对这些相关性的影响。我们使用几何形态测量学量化了头部和两个四杆联动的形状，并将其与每个联动系统的运动传递系数进行比较。两个联动的形状与其机械性能密切相关，并且头部形状似乎限制了两个四杆联动的形状。头部形状促使两个联动之间有更大的整合，与更强的形态-功能相关性以及生物力学重要特征的更高进化速率相关。头部形状限制也可能导致联动运动学中一种微弱但显著的权衡。特别是头部和身体的伸长，似乎通过最大化前后空间可用性来最小化这种权衡的影响。然而，形状与功能之间关系的强度以及头部形状的影响在两个联动之间有所不同，尽管舌骨四杆联动与头部形状限制的独立性更强，但总体上显示出更强的形态-功能关系。
