Data from: Relaxed trait covariance in interspecific cichlid hybrids predicts morphological diversity in adaptive radiations

The process of adaptive radiation involves multiple events of speciation in short succession, associated with ecological diversification. Understanding this process requires identifying the origins of heritable phenotypic variation that allows adaptive radiation to progress. Hybridization is one source of genetic and morphological variation that may spur adaptive radiation. We experimentally explored the potential role of hybridization in facilitating the onset of adaptive radiation. We generated first- and second-generation hybrids of four species of African cichlid fish, extant relatives of the putative ancestors of the adaptive radiations of Lakes Victoria and Malawi. We compared patterns in hybrid morphological variation with the variation in the lake radiations. We show that significant fractions of the interspecific morphological variation and the major trajectories in morphospace that characterize whole radiations can be generated in second-generation hybrids. Furthermore, we show that covariation between traits is relaxed in second-generation hybrids, which may facilitate adaptive diversification. These results support the idea that hybridization can provide the heritable phenotypic diversity necessary to initiate adaptive radiation.

适应辐射（adaptive radiation）过程指短时间内接连发生多起物种形成事件，并伴随生态位分化。解析该过程需探明支撑其推进的可遗传表型变异的起源。杂交是可诱发适应辐射的遗传与形态变异的来源之一。本研究通过实验探究了杂交在推动适应辐射起始过程中的潜在作用：以维多利亚湖与马拉维湖适应辐射类群的推定祖先现存近缘类群——四种非洲慈鲷（African cichlid fish）为实验材料，构建了其第一代与第二代杂交后代，并将杂交后代的形态变异模式与两大湖辐射类群的形态变异模式进行比对。研究结果显示，种间形态变异的显著组分以及表征整个辐射类群的形态空间（morphospace）主要演化轨迹，均可在第二代杂交后代中产生。此外，第二代杂交后代的性状间协变关系被弱化，这或可促进适应性分化。上述结果印证了"杂交可提供启动适应辐射所需的可遗传表型多样性"这一假说。