School of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Department of Earth and Life Science, University of Taipei, Taipei, Taiwan.
J Anim Ecol. 2021 Apr;90(4):967-977. doi: 10.1111/1365-2656.13426. Epub 2021 Feb 8.
The level of dentition asymmetry in snail-eating snakes may reflect their prey choice and feeding efficiency on asymmetric land snails. The three species of Pareas snakes (Squamata: Pareidae) in Taiwan, which form partially sympatric distribution on the island, provide a potential case to test the hypothesis of niche partitioning and character displacement with regard to dentition asymmetry and specialisation in feeding behaviour. In this study, behavioural experiments confirmed that P. formosensis feeds exclusively on slugs, whereas P. atayal and P. komaii consumed both. However, P. atayal more efficiently preys on land snails than P. komaii, exhibiting a shorter handling time and fewer mandibular retractions. Micro-CT and ancestral character reconstruction demonstrated the lowest asymmetry in P. formosensis (the slug specialist), the highest dentition asymmetry in P. atayal (the land snail specialist) and flexibility in P. komaii (the niche switcher): increased dentition asymmetry when sympatrically distributed with the slug eater (character displacement), and decreased asymmetry when living alone (ecological niche release). Ecological niche modelling showed that the distribution of P. formosensis is associated with the presence of slugs, while that of P. atayal could be explained by the land snails. Combining the results from morphology, phylogeny, behavioural experiments and ecological niche modelling, we showed that competition in the sympatric region might have facilitated character displacement among congeners, while the absence of competition in allopatric region has led to ecological niche release.
食蜗牛蛇类的牙齿不对称程度可能反映了它们对不对称陆地蜗牛的猎物选择和进食效率。台湾的三种巴氏蛇（有鳞目：巴氏科）在岛上形成部分同域分布，为检验关于牙齿不对称和进食行为特化的生态位分化和性状替换假说提供了一个潜在案例。在这项研究中，行为实验证实，巴氏巴氏蛇专门以蜗牛为食，而巴氏巴氏蛇和巴氏巴氏蛇则同时食用蜗牛和蜗牛。然而，巴氏巴氏蛇比巴氏巴氏蛇更有效地捕食陆地蜗牛，其处理时间更短，下颌缩回次数更少。微 CT 和祖先特征重建表明，巴氏巴氏蛇（蜗牛专家）的不对称性最低，巴氏巴氏蛇（陆地蜗牛专家）的牙齿不对称性最高，巴氏巴氏蛇（生态位转换者）的灵活性最高：当与食蜗牛者同域分布时，牙齿不对称性增加（性状替换），当独居时，不对称性降低（生态位释放）。生态位模型表明，巴氏巴氏蛇的分布与蜗牛的存在有关，而巴氏巴氏蛇的分布则可以用陆地蜗牛来解释。结合形态学、系统发育、行为实验和生态位模型的结果，我们表明，同域竞争可能促进了近缘种之间的性状替换，而在异域竞争缺失的情况下，则导致了生态位释放。
