Department of Anatomy and Cell Biology, Indiana University School of Medicine, 635 Barnhill Drive, MS 5035, Indianapolis, IN 46202, USA.
Department of Anthropology, The University of Tennessee, 1621 Cumberland Ave., Room 502A, Knoxville, TN 37996, USA; Department of Ecology and Evolutionary Biology, The University of Tennessee, Dabney Hall, 1416 Circle Dr, Knoxville, TN 37996, USA.
J Hum Evol. 2022 Aug;169:103221. doi: 10.1016/j.jhevol.2022.103221. Epub 2022 Jun 27.
Within the primate order, the morphology of the shoulder girdle is immensely variable and has been shown to reflect the functional demands of the upper limb. The observed morphological variation among extant primate taxa consequently has been hypothesized to be driven by selection for different functional demands. Evolutionary analyses of the shoulder girdle often assess this anatomical region, and its traits, individually, therefore implicitly assuming independent evolution of the shoulder girdle. However, the primate shoulder girdle has developmental and functional covariances with the basicranium and pelvic girdle that have been shown to potentially influence its evolution. It is unknown whether these relationships are similar or even present across primate taxa, and how they may affect morphological variation among primates. This study evaluates the strength of covariance and evolutionary potential across four anatomical regions: shoulder girdle, basicranium, pelvis, and distal humerus. Measures of morphological integration and evolutionary potential (conditioned covariance and evolutionary flexibility) are assessed across eight anthropoid primate taxa. Results demonstrate a consistent pattern of morphological constraint within paired anatomical regions across primates. Differences in evolutionary flexibility are observed among primate genera, with humans having the highest evolutionary potential overall. This pattern does not follow functional differences, but rather a separation between monkeys and apes. Therefore, evolutionary hypotheses of primate shoulder girdle morphological variation that evaluate functional demands alone may not account for the effect of these relationships. Collectively, our findings suggest differences in genetic covariance among anatomical regions may have contributed to the observable morphological variation among taxa.
在灵长目动物中，肩带的形态结构变化极大，其形态结构反映了上肢的功能需求。因此，现生物种之间观察到的形态结构变化被假设是由不同功能需求的选择驱动的。对肩带的进化分析经常评估这个解剖区域及其特征，因此隐含地假设肩带是独立进化的。然而，灵长类动物的肩带与颅底和骨盆带在发育和功能上存在相关性，这些相关性可能会影响其进化。目前还不清楚这些关系在灵长类动物中是否相似，甚至是否存在，以及它们可能如何影响灵长类动物之间的形态变化。本研究评估了四个解剖区域（肩带、颅底、骨盆和远端肱骨）之间的协变和进化潜力。评估了 8 种人科灵长类动物的形态整合和进化潜力（条件协变和进化灵活性）的度量。结果表明，在灵长类动物中，配对解剖区域之间存在一致的形态约束模式。在灵长类动物属之间观察到进化灵活性的差异，人类的整体进化潜力最高。这种模式与功能差异无关，而是与猴子和猿之间的分离有关。因此，仅评估功能需求的灵长类动物肩带形态变化的进化假说可能无法解释这些关系的影响。总的来说，我们的研究结果表明，解剖区域之间遗传协变的差异可能导致了观察到的分类群之间的形态变化。
