Major Ecological Transitions in Wild Sunflowers Facilitated by Hybridization

TLDR

Hybridization is common across taxa, yet its contribution to adaptation remains unclear; in sunflowers, extreme‑habitat species are ancient hybrids, suggesting hybrid gene combinations may drive ecological divergence. The authors tested this hypothesis by comparing phenotypes and genomes of ancient hybrids with synthetic hybrids. They found that complementary gene action in synthetic hybrids reproduced most trait differences of ancient hybrids, and the same chromosomal segment combinations were present in both. These results indicate that hybridization facilitated ecological divergence in sunflowers.

Abstract

Hybridization is frequent in many organismal groups, but its role in adaptation is poorly understood. In sunflowers, species found in the most extreme habitats are ancient hybrids, and new gene combinations generated by hybridization are speculated to have contributed to ecological divergence. This possibility was tested through phenotypic and genomic comparisons of ancient and synthetic hybrids. Most trait differences in ancient hybrids could be recreated by complementary gene action in synthetic hybrids and were favored by selection. The same combinations of parental chromosomal segments required to generate extreme phenotypes in synthetic hybrids also occurred in ancient hybrids. Thus, hybridization facilitated ecological divergence in sunflowers.