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.食物竞争驱动取食形态的分化与特化。口足类甲壳动物拥有两类高度特化的取食附肢：一类为细长矛状附肢（spearers），用于伏击逃避性的软躯体猎物；另一类为锤状附肢（smashers），可产生极高冲击力，既能击碎带硬壳的猎物，也能捕获逃避性猎物。为评估附肢类型与取食生态间的关联，本研究对两种同域分布的小型物种（体型范围21~27 mm）的食性展开了比较，二者分别为粉碎型附肢物种与矛刺型附肢物种。本研究采用稳定同位素分析（stable isotope analysis）与贝叶斯混合模型（Bayesian mixing model）MixSIAR，估算了不同猎物类型在物种食性中的占比。两类物种的食性均相对宽泛，涵盖硬壳猎物与软躯体猎物，但二者的猎物占比存在差异：粉碎型附肢物种取食的硬壳猎物占比更高，而矛刺型附肢物种则主要以软躯体猎物为食。已有研究表明，口足类甲壳动物的附肢运动学特征在物种间呈线性缩放关系。这两种小型物种或可产生相似的运动学特征，使其既能捕获逃避性猎物，又能击碎硬壳猎物，进而拓宽了自身的食性范围。但矛刺型附肢物种更擅长捕获逃避性猎物，这意味着小型矛刺型物种在软躯体猎物的竞争中具备更强的竞争力。本研究结果显示，粉碎型附肢物种通过取食硬壳猎物，减少了与矛刺型物种在软躯体猎物上的竞争，进而为极具威力的粉碎式攻击的演化提供了关键选择优势。