Does aquatic foraging impact head shape evolution in snakes?

Evolutionary trajectories are often biased by developmental and historical factors. However, environmental factors can also impose constraints on the evolutionary trajectories of organisms leading to convergence of morphology in similar ecological contexts. The physical properties of water impose strong constraints on aquatic feeding animals by generating pressure waves that can alert prey and potentially push them away from the mouth. These hydrodynamic constraints have resulted in the independent evolution of suction feeding in most groups of secondarily aquatic tetrapods. Despite the fact that snakes cannot use suction they have invaded the aquatic milieu many times independently. Here we test whether the aquatic environment has constrained head shape evolution in snakes and whether shape converges on that predicted by biomechanical models. To do so, we used 3D geometric morphometrics and comparative, phylogenetically informed analyses on a large sample of aquatic snake species. Our ...生物的演化轨迹常受发育与历史因素的影响而产生偏倚。然而，环境因素同样会对生物的演化轨迹施加约束，进而导致相似生态背景下出现形态趋同现象。 水体的物理特性会通过产生压力波对水生摄食动物形成强烈约束——这类压力波可惊动猎物，甚至可能将其推离捕食者的口腔范围。此类流体力学约束，促使多数次水生四足动物（secondarily aquatic tetrapods）类群独立演化出吸吮摄食（suction feeding）策略。 尽管蛇类无法采用吸吮摄食方式，却已多次独立入侵水生生境。本研究旨在检验两个核心问题：一是水生环境是否对蛇类的头部形态演化形成约束，二是蛇类头部形态是否会趋同于生物力学模型所预测的形态。为此，我们针对大量水生蛇类类群样本，采用了三维几何形态测量法（3D geometric morphometrics）以及基于系统发育信息的比较分析方法。本研究……