Massive haplotypes underlie ecotypic differentiation in sunflowers

Area of Science:

• Evolutionary biology
• Genetics
• Ecology

Background:

• Species often comprise ecotypes adapted to diverse environments.
• Mechanisms of ecotype formation and maintenance, especially under hybridization, remain poorly understood.

Purpose of the Study:

• Investigate the genetic basis of ecotypic differentiation in wild sunflowers.
• Identify genomic regions and mechanisms responsible for maintaining adaptive traits across different environments.

Main Methods:

• Resequencing of 1,506 wild sunflowers across three species (Helianthus annuus, H. petiolaris, H. argophyllus).
• Identification and analysis of large, non-recombining haplotype blocks.
• Association analysis of haplotype blocks with ecological traits and environmental factors.

Main Results:

• Discovered 37 large (1-100 Mbp) non-recombining haplotype blocks associated with ecological traits and environmental conditions.
• These blocks maintain adaptive alleles, differentiating sunflower ecotypes and showing significant effects on traits like flowering time and seed size.
• Haplotype blocks are highly divergent, linked to structural variants, and may represent introgressions from related species.

Conclusions:

• Limited recombination within specific haplotype blocks is crucial for maintaining adaptive allele combinations and driving ecotype divergence.
• Structural variation significantly contributes to ecotypic adaptation in wild sunflowers.