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）过程包含短时间内接连发生的多次物种形成事件，且与生态多样化过程密切相关。解析该过程需明确驱动适应辐射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的推定祖先的现存近缘类群——4种非洲慈鲷为实验材料，构建了其第一代及第二代杂交种，并将杂交后代的形态变异模式与湖泊辐射类群的形态变异模式进行对比。本研究证实，第二代杂交种可产生构成种间形态变异的重要组分，以及表征完整辐射类群的形态空间主要演化轨迹。此外，本研究发现第二代杂交种的性状间协变关系有所松弛，这或有助于推动适应性多样化进程。上述结果支持了「杂交可提供启动适应辐射所需的可遗传表型多样性」这一观点。