Data from: The role of feeding morphology and competition in governing the diet breadth of sympatric stomatopod crustaceans

Competition for food drives divergence and specialization in feeding morphology. Stomatopod crustaceans have two kinds of highly specialized feeding appendages: either elongate spear-like appendages (spearers) used to ambush soft-bodied evasive prey or hammer-like appendages (smashers) that produce extremely high forces used both to break hard-shelled prey and to capture evasive prey. To evaluate associations between appendage type and feeding ecology, the diet of two small smasher and spearer species (size range: 21–27 mm) that co-occur were compared. Stable isotope analysis and the Bayesian mixing model MixSIAR were used to estimate the proportional contributions of prey types to the diet. Both species had relatively wide diets that included hard-shelled and soft-bodied prey, albeit in different proportions; the smasher consumed a greater proportion of hard-shelled prey, and the spearer consumed mostly soft-bodied prey. Appendage kinematics in stomatopods is known to scale linearly across species. These two small species may produce similar kinematics allowing them both to capture evasive prey and hammer hard-shelled prey, thereby widening their diets. Yet, the spearer species is more highly adept at capturing evasive prey, indicating that small spearers are stronger competitors for soft-bodied prey. These findings suggest that a smasher's ability to access hard prey reduced competition for soft prey, and therefore conferred an important benefit favouring the evolution of the impressive smashing strike.

食物竞争驱动了摄食形态的分化与特化。口足类甲壳动物（Stomatopod crustaceans）拥有两类高度特化的摄食附肢：一类为细长矛状附肢（spearers，矛击型），用于伏击移动灵活的软体猎物；另一类为锤状附肢（smashers，粉碎型），可产生极高冲击力，既能击碎带硬壳的猎物，也能捕获移动灵活的猎物。为评估附肢类型与摄食生态间的关联，研究对比了两种共存的小型粉碎型与矛击型物种的食性（体型范围：21–27 mm）。研究采用稳定同位素分析（Stable isotope analysis）与贝叶斯混合模型MixSIAR，估算了各类猎物在其食性中的占比。两种物种的食性范围均相对较广，涵盖硬壳与软体猎物，只是占比存在差异：粉碎型物种的硬壳猎物占比更高，而矛击型物种则主要以软体猎物为食。已知口足类动物的附肢运动学（Appendage kinematics）在不同物种间呈线性缩放。这两种小型物种可产生相似的运动学特征，使其既能捕获移动灵活的猎物，也能锤击硬壳猎物，从而拓宽了自身的食性范围。不过，矛击型物种更擅长捕获移动灵活的猎物，这表明小型矛击型物种在软体猎物的竞争中更具优势。上述研究结果表明，粉碎型物种获取硬壳猎物的能力减少了其在软体猎物上的竞争压力，因此为极具冲击力的粉碎式攻击的演化提供了重要的选择优势。