Tamagnini Davide, Stephenson Jamie, Brown Richard P, Meloro Carlo
Dipartimento di Scienze Biologiche, Geologiche ed Ambientali, Università di Bologna, Via Selmi, 3, 40126 Bologna, Italy.
Research Centre in Evolutionary Anthropology and Palaeoecology, School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, UK.
Zoology (Jena). 2018 Aug;129:25-34. doi: 10.1016/j.zool.2018.05.008. Epub 2018 May 22.
The non-venomous grass snake (Natrix helvetica) and the venomous adder (Vipera berus) are two native species that are often found in sympatry in Great Britain and Europe. They occupy partially overlapping ecological niches and prey on small vertebrates, but use different feeding strategies. Here, we investigated the morphologies of grass snakes and adders from Dorset (UK) using two-dimensional geometric morphometrics to assess the degree of sexual dimorphism in size and shape together with the relative impact of allometry and general body dimensions on head shape. Both species showed significant sexual dimorphism in head size, but not in head shape. We found a clear allometric pattern in N. helvetica, whereas allometry in V. berus was generally less pronounced. Body dimensions were strongly correlated with head shape in the grass snake, but not in the adder. The fact that V. berus is venomous appears to explain the lack of allometric patterns and the lack of an association between body dimensions and head shape. The high degree of size dimorphism identified in both species could originate from the advantages of reduced intraspecific competition that are conveyed by a partial differentiation in feeding morphology.
无毒的草蛇（Natrix helvetica）和有毒的蝰蛇（Vipera berus）是两种本土物种，在英国和欧洲经常同域分布。它们占据部分重叠的生态位，以小型脊椎动物为食，但采用不同的捕食策略。在这里，我们使用二维几何形态测量学研究了来自英国多塞特郡的草蛇和蝰蛇的形态，以评估大小和形状上的两性异形程度，以及异速生长和总体身体尺寸对头部形状的相对影响。两个物种在头部大小上均表现出显著的两性异形，但在头部形状上没有。我们在草蛇中发现了明显的异速生长模式，而蝰蛇中的异速生长通常不太明显。在草蛇中，身体尺寸与头部形状密切相关，但在蝰蛇中并非如此。蝰蛇有毒这一事实似乎可以解释异速生长模式的缺乏以及身体尺寸与头部形状之间缺乏关联的现象。在这两个物种中发现的高度大小二态性可能源于进食形态的部分分化所带来的种内竞争减少的优势。
