Data from: Divergent in shape and convergent in function: adaptive evolution of the mandible in Sub-Antarctic mice

Convergent evolution in similar environments constitutes strong evidence of adaptive evolution. Transported with people around the world, house mice colonized even remote areas, such as Sub-Antarctic islands. There, they returned to a feral way of life, shifting towards a diet enriched in terrestrial macroinvertebrates. Here, we test the hypothesis that this triggered convergent evolution of the mandible, a morphological character involved in food consumption. Mandible shape from four Sub-Antarctic islands was compared to phylogeny, tracing the history of colonization, and climatic conditions. Mandible shape was primarily influenced by phylogenetic history, thus discarding the hypothesis of convergent evolution.
The biomechanical properties of the jaw were then investigated. Incisor in-lever and temporalis out-lever suggested an increase in the velocity of incisor biting, in agreement with observations on various carnivorous and insectivorous rodents. The mechanical advantage related to incisor biting also revealed an increased functional performance in Sub-Antarctic populations, and appears to be an adaptation to catch prey more efficiently. The amount of change involved was larger than expected for a plastic response, suggesting microevolutionary processes were evolved.
This study thus denotes some degree of adaptive convergent evolution related to changes in habitat-related changes in dietary items in Sub-Antarctic mice, but only regarding simple, functionally relevant aspects of mandible morphology.

趋同演化（convergent evolution）是适应性演化（adaptive evolution）的有力佐证。家鼠随人类活动被携带至全球各地，甚至成功殖民了亚南极岛屿（Sub-Antarctic islands）等偏远区域。在这些岛屿上，它们回归野生生活状态，饮食结构转向以陆生大型无脊椎动物为主。本研究检验了如下假说：这种饮食转变触发了下颌骨（mandible）——参与食物摄取的形态学特征——的趋同演化。研究对比了四个亚南极岛屿种群的下颌骨形态，并结合殖民历史的系统发育（phylogeny）关系与气候条件展开分析。结果显示，下颌骨形态主要受系统发育历史的影响，因此不支持该趋同演化假说。
随后，研究团队对颌骨的生物力学特性（biomechanical properties）进行了探究。门齿内杠杆（incisor in-lever）与颞肌外杠杆（temporalis out-lever）的分析结果表明，门齿咬击的速度有所提升，这与多种食肉性、食虫性啮齿类的观测结果相符。与门齿咬食相关的机械优势（mechanical advantage）也显示，亚南极种群的功能性能得到增强，这似乎是为更高效捕获猎物而演化出的适应性特征。该变化的幅度远超表型可塑性反应（plastic response）的预期水平，提示背后存在微演化进程（microevolutionary processes）。
综上，本研究表明，亚南极家鼠因栖息地饮食结构改变而产生的适应性趋同演化仅存在一定程度的体现，且仅局限于下颌骨形态中与功能相关的简单特征方面。