How head shape and substrate particle size affect fossorial locomotion in lizards

Granular substrates ranging from silt to gravel cover much of the Earth’s land area, providing an important habitat for fossorial animals. Many of these animals use their heads to penetrate the substrate. Although there is considerable variation in head shape, how head shape affects fossorial locomotor performance in different granular substrates is poorly understood. Here, head shape variation for 152 species of fossorial lizards was quantified for head diameter, slope and pointiness of the snout. The force needed to penetrate different substrates was measured using 28 physical models spanning this evolved variation was constructed. Ten substrates were considered, ranging in particle size from 0.025 to 4mm in diameter and consisting of spherical or angular particles. Head shape evolved in a weakly correlated manner, with snouts that were gently sloped being blunter. There were also significant clade differences in head shape among fossorial lizards. Experiments with physical models sho...

从粉砂到砾石的粒状基质（granular substrates）覆盖了地球陆地总面积的绝大部分，为穴居动物（fossorial animals）提供了关键栖息生境。多数这类动物依靠头部钻入基质中。尽管头部形态存在显著差异，但目前学界对头部形态如何影响不同粒状基质中的穴居运动性能仍缺乏深入认知。本研究针对152种穴居蜥蜴的头部形态变异展开量化分析，量化指标涵盖头部直径、吻部坡度与吻部尖锐度。我们构建了28个覆盖该类群演化变异范围的物理模型，用以测量钻入不同基质所需的作用力。实验共设置10种基质，其粒径范围为0.025至4毫米，颗粒形态包含球形与棱角形两类。头部形态的演化呈现弱相关特征：吻部坡度平缓的个体，其吻部更为钝圆。穴居蜥蜴的头部形态在不同演化支（clade）之间亦存在显著差异。基于物理模型的实验结果显示……