Hybridization and a mixture of small and large-effect loci facilitate adaptive radiation

Abstract

Adaptive radiations represent some of the most remarkable explosions of diversification across the tree of life. However, the constraints to rapid diversification and how they are sometimes overcome, particularly the relative roles of genetic architecture and hybridization, remain unclear. Here, we address these questions in the Alpine whitefish radiation, using a whole-genome dataset that includes multiple individuals of each of the 22 species belonging to six ecologically distinct ecomorph classes across several lake-systems. We reveal that repeated ecological and morphological diversification along a common environmental axis is associated with both genome-wide allele frequency shifts and a specific, larger effect, locus, associated with the gene edar. Additionally, we highlight the role of introgression between species from different lake-systems in facilitating the evolution and persistence of species with unique phenotypic combinations and ecology. These results highlight the role of both genome architecture and secondary contact with hybridization in fuelling adaptive radiation.

The explosive radiation of the NeotropicalTillandsiasubgenusTillandsia(Bromeliaceae) has been facilitated by pervasive hybridization

“…D-statistics revealed both recent and ancient gene flow while allele sharing did not compromise species or clade boundaries. Notably, the obtained f b (C) ranges were in general far higher than those previously inferred for ancestral introgressions between species of Malawi cichlids (Malinsky et al 2018) or of hares (Ferreira et al 2021), but comparable to other rapid radiations (De-Kayne et al 2022; Slovak et al 2023; Suvorov et al 2022). The interplay of genomic signals and our limited clade sampling complicate inference on the timing of gene-flow events, yet their high prevalence suggests they occured during both ancestral and recent history.…”

Phylogenomic analysis of the Lake Kronotskoe species flock of Dolly Varden charr reveals genetic and developmental signatures of sympatric radiation

“…We also determined that the Lake Kronotskoe lineages maintain reproductive isolation through low hybridization. By contrast, the much older Lake Malawi cichlid radiation, has f -branch values commonly exceeding 5% and up to 14.2% (19) and Coregonus salmonids also have extensive introgression (57). These new data suggest that the species flock in Lake Kronotskoe was established by a single founding population having shared genetic signatures that quickly established and maintained thoroughly reproductively isolated populations.…”