Major stages of vertebrate adaptive radiation are assembled from a disparate spatiotemporal landscape

To investigate the origins and stages of vertebrate adaptive radiation, we reconstructed the spatial and temporal histories of genetic variants underlying major phenotypic axes of diversification from the genomes of 202 Caribbean pupfishes. Ancient standing variation from disparate spatial sources was reassembled into new combinations which are under strong selection for adaptation to novel trophic niches on only a single island throughout the Caribbean. This occurred in three stages: first, standing variation associated with feeding behavior swept, then standing variation regulating craniofacial development and pigmentation, and finally de novo variation for craniofacial development. Our results provide clear support for two longstanding hypotheses about adaptive radiation and demonstrate how ancient alleles maintained for millennia in distinct environmental refugia can be assembled into new adaptive combinations.