Speciation genetics of biological invasions with hybridization

The negative effects of human-induced habitat disturbance and modification on multiple dimensions of biological diversity are well chronicled (Turner 1996; Harding et al. 1998; Lawton et al. 1998; Sakai et al. 2001). Among the more insidious consequences is secondary contact between formerly allopatric taxa (Anderson & Hubricht 1938; Perry et al. 2002; Seehausen 2006). How the secondary contact will play out is unpredictable (Ellstrand et al. 2010), but if the taxa are not fully reproductively isolated, hybridization is likely, and if the resulting progeny are fertile, the eventual outcome is often devastating from a conservation perspective (Rhymer & Simberloff 1996; Wolf et al. 2001; McDonald et al. 2008). In this issue of Molecular Ecology, Steeves et al. (2010) present an analysis of hybridization between two avian species, one of which is critically endangered and the other of which is invasive. Their discovery that the endangered species has not yet been hybridized to extinction is promising and not what one would necessarily expect from theory.