While hybrid plants might be less successful than their parents, if enough survive they can backcross with a parent species. This can help a parent colonise a new territory.
Older landscapes are expected to be home to older, more genetically well-defined taxa with greater reproductive barriers.
When species cohesion is maintained despite ongoing natural hybridisation.
A study of potential scent mediation of prezygotic and postzygotic reproductive isolation in Ipomopsis aggregata and I. tenuituba.