Data from: Developmental dynamics of ecomorphological convergence in a transcontinental lizard radiation

Phenotypic convergence has confounded evolutionary biologists for centuries, explained as adaptations to shared selective pressures, or alternatively, the result of limited developmental pathways. We tested the relative roles of adaptation and constraint in generating convergent cranial morphologies across a large lizard radiation, the Lacertidae, whose members inhabit diverse environments throughout the Old World and display high amounts of homoplasy associated with ecological niche. Using three-dimensional X-ray computed tomography, we quantified cranial shape variation associated with ontogeny, allometry, and ecology, covering all lacertid genera and one-third of species diversity. Landmark-based geometric morphometrics showed that cranial shape varied significantly among biomes, with substantial convergence among arid-dwelling lineages. Comparisons of species ontogenetic growth trajectories between biomes revealed that allometric postdisplacement, as evidenced by decreased elevation of a constant slope, drives the convergent paedomorphic appearance of independent arid-dwelling forms. We hypothesize that observed heterochronic changes reflect temporal compression of ancestral life history in response to extreme environments, with associated phenotypes occurring as by-products of adaptive shifts in reproductive investment. Although allometry has long been considered a developmental constraint, our results demonstrate that allometric flexibility during early ontogeny produces convergent ecomorphologies over vast temporal and spatial scales, thus dramatically obscuring underlying phylogenetic signals.表型趋同（phenotypic convergence）数百年来一直困扰着进化生物学家，其成因既被阐释为对共同选择压力的适应性演化，也可归因于发育通路受限的结果。本研究针对大型蜥蜴辐射演化类群——蜥蜴科（Lacertidae），检验了适应性演化与发育限制在产生趋同颅骨形态中的相对作用。该类群遍布旧大陆各类生境，且存在大量与生态位相关的同塑现象（homoplasy）。本研究采用三维X射线计算机断层成像（three-dimensional X-ray computed tomography）技术，对覆盖蜥蜴科所有属类及三分之一物种多样性的类群，量化了其与个体发育（ontogeny）、异速生长（allometry）及生态环境相关的颅骨形状变异。基于标志点的几何形态测量学（landmark-based geometric morphometrics）分析显示，不同生物群区间的颅骨形状存在显著差异，耐旱支系间存在显著趋同演化。对不同生物群区物种种体发育生长轨迹的比较表明，异速生长后置位移（allometric postdisplacement，表现为恒定斜率下的发育高度降低）驱动了各独立耐旱类群趋同的幼态持续（paedomorphosis）表型。本研究推测，观测到的异时性变化（heterochronic changes）反映了为适应极端环境而发生的祖先生活史事件的时间压缩，相关表型作为繁殖投入适应性转变的副产物出现。尽管异速生长长期以来被视为发育限制因素，本研究结果表明，早期个体发育阶段的异速生长可塑性能够在广阔的时空尺度上产生趋同生态形态，从而极大地掩盖了潜在的系统发育信号（phylogenetic signals）。