Data from: Genetic dissection of adaptive form and function in rapidly-speciating cichlid fishes

Genes of major phenotypic effects and strong genetic correlations can facilitate adaptation, direct selective responses and potentially lead to phenotypic convergence. However, the preponderance of this type of genetic architecture in repeatedly-evolved adaptations remains unknown. Using hybrids between Haplochromis chilotes (thick-lipped) and H. nyererei (thin-lipped) we investigated the genetics underlying hypertrophied lips and elongated heads, traits that evolved repeatedly in cichlids. At least 25 loci of small-to-moderate and mainly additive effects were detected. Phenotypic variation in lip and head morphology was largely independent. Although several QTL overlapped for lip and head morphology traits, they were often of opposite effects. The distribution of effect signs suggests strong selection on lips. The fitness implications of several detected loci were demonstrated using a laboratory assay testing for the association between genotype and variation in foraging performance. The persistence of low fitness alleles in head morphology appears to be maintained through antagonistic pleiotropy/close linkage with positive-effect lip morphology alleles. Rather than being based on few major loci with strong positive genetic correlations, our results indicate that the evolution of the Lake Victoria thick-lipped ecomorph is the result of selection on numerous loci distributed throughout the genome.

具有显著表型效应与强遗传相关性的基因，可推动适应性演化、介导选择响应，并可能引发表型趋同。然而，这类遗传结构在重复演化的适应性性状中的普遍性仍未明确。本研究以厚唇朴丽鱼（Haplochromis chilotes）与细唇朴丽鱼（H. nyererei）的杂交后代为实验材料，探究了肥大唇部与延长头部这一在丽鱼科鱼类中反复演化的性状的遗传基础。研究共检测到至少25个效应量介于中小水平、且以加性效应为主的基因座。唇部与头部形态的表型变异在很大程度上相互独立。尽管多个数量性状基因座（QTL）在唇部与头部形态性状上存在重叠，但这些基因座的效应往往方向相反。效应符号的分布特征表明，唇部受到了强烈的正向选择。本研究通过实验室实验检测基因型与觅食性能变异之间的关联，证实了多个检测到的基因座的适合度效应。头部形态中低适合度等位基因的持续存在，似乎是通过拮抗多效性/与具有正效应的唇部形态等位基因紧密连锁得以维持的。本研究结果表明，维多利亚湖厚唇生态型的演化并非依赖于少数具有强正遗传相关性的主要基因座，而是由分布于整个基因组的众多基因座上的选择作用所驱动的。