Data from: Malagasy cichlids differentially limit impacts of body shape evolution on oral jaw functional morphology

Patterns of trait covariation, like integration and modularity, are vital factors that influence the evolution of vertebrate body plans. In functional systems, decoupling of morphological modules buffers functional change in one trait by reducing correlated variation with another. However, for complex morphologies with many-to-one mapping of form to function (MTOM), resistance to functional change may also be achieved by constraining morphological variation within a functionally stable region of morphospace. For this research, we used geometric morphometrics to evaluate the evolution of body shape and its relationship to jaw functional morphology in two independent radiations of endemic Malagasy cichlid (Teleostei: Cichlidae). Our results suggested that the two subfamilies used different strategies to mitigate impacts of body shape variation on a metric of jaw function, maxillary kinematic transmission (MKT): (1) modularity between cranial and postcranial morphologies, and (2) integration of body and jaw evolution, with jaw morphologies varying in a manner that limits change in MKT. This research shows that, unlike modularity, MTOM allows traits to retain strong evolutionary covariation while still reducing impacts on functionality. These results suggest that MTOM, and its influence on the evolution of correlated traits, is likely much more widespread than is currently understood.

性状协变模式（如整合与模块化）是影响脊椎动物躯体构型演化的关键因素。在功能系统中，形态模块的解耦可通过降低与另一性状的相关变异，缓冲某一性状的功能变化。然而，对于存在形-功能多对一映射（many-to-one mapping of form to function, MTOM）的复杂形态结构而言，通过将形态变异限制在形态空间内的功能稳定区域中，也可实现对功能变化的抵抗。本研究采用几何形态测量学（geometric morphometrics）方法，对两独立辐射演化的马达加斯加特有慈鲷（Teleostei: Cichlidae）类群的体形演化及其与颌部功能形态的关联进行了评估。研究结果显示，两个慈鲷亚科采用了不同策略以减轻体形变异对颌功能指标——上颌运动传递（maxillary kinematic transmission, MKT）——的影响：其一为颅部与颅后形态间的模块化策略；其二为体形与颌部演化的整合策略，即颌部形态的变异方式可限制MKT的变化。本研究表明，与模块化策略不同，MTOM可在保留性状间强演化协变关系的同时，降低其对功能的负面影响。上述结果提示，MTOM及其对相关性状演化的影响，其实际分布范围可能远超当前学界的认知。