Data from: Divergent selection drove the early diversification of locomotor morphology in the radiation of Neotropical geophagine cichlids

Background: Simpson envisaged a conceptual model of adaptive radiation in which lineages diversify into "adaptive zones" within a broad adaptive landscape. However only a handful of studies have actually investigated the adaptive landscape and its implication for our interpretation of the underlying mechanisms of phenotypic evolution. In fishes the evolution of locomotor phenotypes may represent an important dimension of ecomorphological diversification during an adaptive radiation given its implications for feeding and habitat use. Neotropical geophagine cichlids represent a newly identified adaptive radiation and provide a useful system for studying patterns of locomotor diversification and the implications of selective constraints on phenotypic divergence in general. Results: We use multivariate ordination models of phenotypic evolution and posterior predictive approaches to investigate the adaptive landscape and test for evidence of early diversification of locomotor phenotypes in Geophagini. The evolution of locomotor phenotypes was characterized by divergent selection towards two distinct adaptive peaks and the early divergence of modern morphological disparity. Evolutionary models and posterior predictive approaches favoured constant-rate divergent selection over decreasing rates of phenotypic evolution as the underlying process driving the early divergence of locomotor phenotypes. Conclusions: The influence of multiple adaptive peaks on the divergence of locomotor attributes in Geophagini is compatible with the expectations of an ecologically-driven adaptive radiation. This study confirms that the diversification of locomotor morphology represents an important dimension of phenotypic evolution in the geophagine adaptive radiation. It also suggests that the commonly observed early burst of phenotypic evolution during adaptive radiations is best explained by a model that incorporates divergent selection deep in the phylogeny.

**背景**：辛普森构想了适应性辐射（adaptive radiation）的概念模型，该模型提出谱系可在广阔的适应性景观（adaptive landscape）中分化为多个‘适应性区域（adaptive zone）’。然而，仅有少数研究真正探究了适应性景观及其对我们理解表型进化（phenotypic evolution）底层机制的启示。就鱼类而言，鉴于运动表型（locomotor phenotypes）的进化与摄食策略及栖息地利用紧密关联，其可能代表了适应性辐射过程中生态形态分化（ecomorphological diversification）的重要维度。新热带区的土鲷族（Geophagini）慈鲷是新近被发现的适应性辐射类群，为研究运动模式分化以及选择限制对表型分化的一般性启示提供了优质研究体系。

**结果**：本研究借助表型进化的多元排序模型（multivariate ordination models）与后验预测方法（posterior predictive approaches），探究土鲷族的适应性景观，并检验其运动表型早期分化的相关证据。运动表型的进化以朝向两个不同适应性峰值（adaptive peaks）的歧化选择（divergent selection），以及现代形态分异度（morphological disparity）的早期分化为特征。进化模型与后验预测方法均支持，驱动运动表型早期分化的底层过程为恒定速率的歧化选择，而非表型进化速率随时间递减的过程。

**结论**：多个适应性峰值对土鲷族运动性状（locomotor attributes）分化的影响，符合生态驱动型适应性辐射的理论预期。本研究证实，运动形态的分化是土鲷族适应性辐射过程中表型进化的重要维度。本研究同时表明，适应性辐射过程中普遍观测到的表型进化早期爆发现象，最佳可通过整合了系统发育（phylogeny）深处歧化选择的模型予以解释。