Dune Adaptation Facilitates Speciation in Sunflowers

Sister sunflower taxa are often found in divergent habitats. For example, both H. neglectus and an ecotype of H. petiolaris inhabit active sand dunes while their closest relative is found on sand sheets. We explore ecological divergence in these two dune systems and assess their progress towards speciation. We find that larger seeds have evolved in both dune habitats and that the genetic basis of those differences are similar. We also find that assortative mating via conspecific pollen precedence arose surprisingly early between the H. petiolaris ecotypes while major chromosomal change is associated with the evolution of H. neglectus. Ultimately, understanding the similarities and differences between these systems will help answer the question - how predictable is speciation?