Hybridization is thought to have played an important role in shaping the evolutionary history of diverse island taxa. Yet secondary contact doesn’t always result in introgressive hybridization, and it is important to consider the wide range of ecological and evolutionary outcomes of secondary contact, particularly in the face of widespread secondary contact between island endemics and recently introduced species. While there are biological reasons to predict secondary contact and heterospecific mating to be common on islands for many taxa, there are also reasons to expect that the consequences of secondary contact will differ depending on the nature of the species involved. We present the results from a quantitative analysis of published empirical research on secondary contact on remote oceanic islands for 705 vertebrate, invertebrate, and plant species spanning 167 genera and 99 families, with a focus on the Canary Islands, the Galápagos Islands, New Zealand, the Caribbean, and Hawaii. We weigh evidence for the drivers of secondary contact and heterospecific mating in these systems. In particular, we compare cases of secondary contact between endemic species versus secondary contact between endemic and introduced species. We find that the three main drivers of secondary contact and heterospecific mating on islands most frequently reported in the literature are disturbance, long-distance (e.g. inter-island) dispersal, and compromised assortative mating. We find support for the hypothesis that introgression is a more common outcome between endemic species while reproductive interference is a more common outcome between endemic and introduced species. Contact between recently-diverged endemic species is likely responsible for the apparent frequency of hybridization on islands, whereas reproductive interference between endemic and introduced species presents a cryptic and underappreciated conservation threat to endemic island taxa.
Endemic species, introduced species, and two faces of secondary contact on oceanic islands
Abstract ID: 13
Event: The 3rd AsiaEvo Conference
Topic: Impact of introgessive hybridization on tropical diversification
Presenter Name: Todd Vision