Affiliation: College of Arts and Sciences, Department of Biology
Other Affiliation: Department of Ecology and Evolutionary Biology, University of Arizona
Hybridization is thought to have played an important role in shaping the evolutionary history of diverse island taxa. Here, we propose an ecological and evolutionary framework for understanding the causes and consequences of heterospecific mating on islands – with and without hybridization. There are a number of reasons why secondary contact is expected to be unusually frequent on islands and why heterospecific mating may be a frequent result of such secondary contact. An important contributor is the suite of species and community traits that are enriched by the colonization process itself. The consequences of heterospecific mating may depend, to a large degree, on whether one of the species is introduced. Due to generally weak intrinsic reproductive isolation between island endemics, secondary contact will frequently lead to hybrid establishment and interspecific gene flow. By contrast, due to relatively longer divergence times between endemic and introduced taxa, there will typically be strong postzygotic isolation between them, and recurrent mating within zones of secondary contact will often lead instead to local exclusion by reproductive interference. Since recent human activity is bringing many insular endemics into contact with introduced relatives, this latter outcome may be an underappreciated conservation threat.