Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, 48109, USA.
Museum of Zoology, University of Michigan, Ann Arbor, Michigan, 48109, USA.
BMC Ecol Evol. 2023 Sep 8;23(1):48. doi: 10.1186/s12862-023-02157-3.
Dipsadine snakes represent one of the most spectacular vertebrate radiations that have occurred in any continental setting, with over 800 species in South and Central America. Their species richness is paralleled by stunning ecological diversity, ranging from arboreal snail-eating and aquatic eel-eating specialists to terrestrial generalists. Despite the ecological importance of this clade, little is known about the extent to which ecological specialization shapes broader patterns of phenotypic diversity within the group. Here, we test how habitat use and diet have influenced morphological diversification in skull shape across 160 dipsadine species using micro-CT and 3-D geometric morphometrics, and we use a phylogenetic comparative approach to test the contributions of habitat use and diet composition to variation in skull shape among species.
We demonstrate that while both habitat use and diet are significant predictors of shape in many regions of the skull, habitat use significantly predicts shape in a greater number of skull regions when compared to diet. We also find that across ecological groupings, fossorial and aquatic behaviors result in the strongest deviations in morphospace for several skull regions. We use simulations to address the robustness of our results and describe statistical anomalies that can arise from the application of phylogenetic generalized least squares to complex shape data.
Both habitat and dietary ecology are significantly correlated with skull shape in dipsadines; the strongest relationships involved skull shape in snakes with aquatic and fossorial lifestyles. This association between skull morphology and multiple ecological axes is consistent with a classic model of adaptive radiation and suggests that ecological factors were an important component in driving morphological diversification in the dipsadine megaradiation.
树栖吞食蜗牛的蛇类和吞食鳗鱼的水栖蛇类，以及在陆地生活的蛇类等，这些令人惊叹的生态多样性都代表了在任何大陆环境中发生的最壮观的脊椎动物辐射之一，在中美洲和南美洲拥有超过 800 种蛇类。尽管这个分支具有重要的生态意义，但对于生态特化在多大程度上塑造了该群体中更广泛的表型多样性模式，人们知之甚少。在这里，我们使用微 CT 和 3D 几何形态测量法，通过 160 种树栖吞食蜗牛的蛇类物种来测试栖息地利用和饮食如何影响颅骨形状的形态多样化，并使用系统发育比较方法来检验栖息地利用和饮食组成对物种间颅骨形状变化的贡献。
我们证明，虽然栖息地利用和饮食都是颅骨许多区域形状的重要预测因子，但与饮食相比，栖息地利用在更多的颅骨区域显著预测了形状。我们还发现，在生态分组中，穴居和水生行为导致了几个颅骨区域的形态空间中最强的偏离。我们使用模拟来解决我们结果的稳健性，并描述了应用系统发育广义最小二乘法处理复杂形状数据时可能出现的统计异常。
栖息地和饮食生态在树栖吞食蜗牛的蛇类中与颅骨形状显著相关；与水生和穴居生活方式相关的蛇类颅骨形状关系最强。这种颅骨形态与多个生态轴之间的关联与经典的适应辐射模型一致，表明生态因素是驱动树栖吞食蜗牛的蛇类巨辐射形态多样化的一个重要组成部分。
