Laboratory of Functional Morphology, Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium.
School of Zoology & the Steinhardt Museum of Natural History, Tel Aviv University, Tel Aviv 6997801, Israel.
Biol Lett. 2023 Nov;19(11):20230395. doi: 10.1098/rsbl.2023.0395. Epub 2023 Nov 22.
A phylogenetically diverse minority of snake and lizard species exhibit rostral and ocular appendages that substantially modify the shape of their heads. These cephalic horns have evolved multiple times in diverse squamate lineages, enabling comparative tests of hypotheses on the benefits and costs of these distinctive traits. Here, we demonstrate correlated evolution between the occurrence of horns and foraging mode. We argue that although horns may be beneficial for various functions (e.g. camouflage, defence) in animals that move infrequently, they make active foragers more conspicuous to prey and predators, and hence are maladaptive. We therefore expected horns to be more common in species that ambush prey (entailing low movement rates) rather than in actively searching (frequently moving) species. Consistent with that hypothesis, our phylogenetic comparative analysis of published data on 1939 species reveals that cephalic horns occur almost exclusively in sit-and-wait predators. This finding underlines how foraging mode constrains the morphology of squamates and provides a compelling starting point for similar studies in other animal groups.
少数蛇和蜥蜴物种在进化上具有多样性，它们的头部具有显著的额前和眼部附属物，从而改变了头部的形状。这些头部角已经在不同的有鳞目动物谱系中多次进化，使关于这些独特特征的益处和成本的假设能够进行比较测试。在这里，我们证明了角的出现与觅食方式之间存在相关性。我们认为，尽管角对于那些不常移动的动物的各种功能（例如伪装、防御）可能是有益的，但它们使积极觅食者对猎物和捕食者更加显眼，因此是适应不良的。因此，我们预计角会更常见于埋伏猎物的物种（意味着移动速度较低），而不是积极搜索猎物的物种（经常移动）。我们对 1939 个物种的已发表数据进行的系统发育比较分析与该假说一致，揭示了头部角几乎只存在于等待捕食的捕食者中。这一发现强调了觅食方式如何限制了有鳞目动物的形态，并为其他动物群体的类似研究提供了一个有力的起点。
