Hybridization alters the shape of the genotypic fitness landscape, increasing access to novel fitness peaks during adaptive radiation

Estimating the complex relationship between fitness and genotype or phenotype (i.e. the adaptive landscape) is one of the central goals of evolutionary biology. However, adaptive walks connecting genotypes to organismal fitness, speciation, and novel ecological niches are still poorly understood and processes for surmounting fitness valleys remain controversial. One outstanding system for addressing these connections is a recent adaptive radiation of ecologically and morphologically novel pupfishes (a generalist, molluscivore, and scale-eater) endemic to San Salvador Island, Bahamas. We leveraged whole-genome sequencing of 139 hybrids from two independent field fitness experiments to identify the genomic basis of fitness, estimate genotypic fitness networks, and measure the accessibility of adaptive walks on the fitness landscape. We identified 132 SNPs that were significantly associated with fitness in field enclosures. Six out of the 13 regions most strongly associated with fitness co...估算适合度（fitness）与基因型（genotype）或表型（phenotype）之间的复杂关联（即适应性景观（adaptive landscape）），是进化生物学的核心研究目标之一。然而，将基因型与生物体适合度、物种形成以及新兴生态位相连的适应性行走（adaptive walk）机制，目前仍知之甚少，而跨越适合度谷（fitness valley）的过程也尚存争议。用于解析这类关联的杰出研究体系之一，是近期在巴哈马圣萨尔瓦多岛发现的、发生适应辐射且具有全新生态与形态特征的特有鳉鱼（pupfish）类群，该类群涵盖泛食性、食软体动物型与食鳞型三种生态型。本研究利用两项独立野外适合度实验中获得的139个杂交个体的全基因组测序数据，旨在鉴定适合度的基因组基础、估算基因型适合度网络，并量化适应性行走在适应性景观上的可达性。本研究共鉴定出132个在野外围栏实验中与适合度显著相关的单核苷酸多态性位点（Single Nucleotide Polymorphism, SNP）。在与适合度关联最为紧密的13个基因组区域中，有6个区域的