title: Multiple reproductive barriers separate recently diverged sunflower ecotypes.
abstract: Measuring reproductive barriers between groups of organisms is an effective way to determine the traits and mechanisms that impede gene flow. However, to understand the ecological and evolutionary factors that drive speciation, it is important to distinguish between the barriers that arise early in the speciation process and those that arise after speciation is largely complete. In this article, we comprehensively test for reproductive isolation between recently diverged (<10,000 years bp) dune and nondune ecotypes of the prairie sunflower, Helianthus petiolaris. We find reproductive barriers acting at multiple stages of hybridization, including premating, postmating-prezygotic, and postzygotic barriers, despite the recent divergence. Barriers include extrinsic selection against immigrants and hybrids, a shift in pollinator assemblage, and postpollination assortative mating. Together, these data suggest that multiple barriers can be important for reducing gene flow in the earliest stages of speciation.
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada. kate.ostevik@gmail.com.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Ostevik
authors.affiliation: School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
authors.forename: Rose L
authors.initials: RL
authors.lastname: Andrew
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Sarah P
authors.initials: SP
authors.lastname: Otto
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.|Department of Biology, Indiana University, Bloomington, Indiana.
authors.forename: Loren H
authors.initials: LH
authors.lastname: Rieseberg
mesh_terms: D060146:Ecotype; D049810:Genetic Speciation; D006368:Helianthus / Q000235:genetics* / Q000502:physiology; D006824:Hybridization, Genetic; D054817:Pollination; D060047:Reproductive Isolation; D012641:Selection, Genetic
keywords: Ecological divergence; Helianthus petiolaris; incipient speciation; pollen competition; reciprocal transplant; sand dune adaptation