Data from: Imperfect morphological convergence: variable changes in cranial structures underlie transitions to durophagy in moray eels

Convergence is central to the study of evolution because it demonstrates the power of natural selection to deterministically shape phenotypic diversity. However, the conditions under which a common morphology repeatedly evolves may be restrictive. Many factors—such as differing genetic and environmental backgrounds and many-to-one mapping of form to function—contribute to variability in responses to selection. Nevertheless, lineages may evolve similar, even if not identical, forms given a shared selective regime, providing opportunities to examine the relative importance of natural selection, constraint and contingency. Here, we show that following 10 transitions to durophagy in moray eels (Muraenidae), cranial morphology repeatedly evolved toward a novel region of morphological space indicative of enhanced feeding performance on hard prey. Disparity among the resulting 15 durophagous species, however, is greater than disparity among ancestors that fed on large evasive prey, contradicting the pattern expected under convergence. This elevated disparity is a consequence of lineage-specific responses to durophagy, in which independent transitions vary in the suites of traits exhibiting the largest changes. Our results reveal a pattern of imperfect convergence, which suggests shared selection may actually promote diversification because lineages often differ in their phenotypic responses to similar selective demands.

趋同演化（convergence）是演化生物学研究的核心议题，因其直观展现了自然选择以确定性路径塑造表型多样性的强大能力。然而，重复演化出同一形态的前提条件往往具有限制性。诸多因素——如差异化的遗传与环境背景、形态-功能的多对一映射关系等——都会导致类群对选择的响应存在差异。尽管如此，若类群处于共同的选择情境（selective regime）下，仍可演化出相似（即便并非完全一致）的形态，这为探究自然选择、演化限制与偶然性的相对重要性提供了研究契机。本研究针对海鳗科（Muraenidae）的10次硬食性（durophagy）演化转变展开分析，结果显示其颅部形态反复向形态空间的全新区域演化，该特征表明这些类群在硬壳猎物的摄食性能上得到了显著提升。然而，由此产生的15种硬食性海鳗的形态差异度（disparity），高于其以大型闪避猎物为食的祖先类群的形态差异度，这与趋同演化下的预期模式相悖。这种升高的形态差异度，源于不同类群对硬食性的特异性响应：各独立演化转变类群中，发生显著变化的性状组合各不相同。本研究结果揭示了一种不完全趋同演化的模式，该模式表明，共同的选择压力实则可能促进类群的多样化，因为不同类群对相似选择需求的表型响应往往存在差异。