Rapid morphological change of non-native frugivores on the Hawaiian island of O’ahu

Novel ecosystems have become widespread created, in part, by the global spread of species. The non-native species in these environments can be under intense evolutionary pressures that cause rapid morphological change, which can then influence species interactions. In Hawai’i, much of the native frugivore community is extinct, replaced by non-native bird species. Here, we determined if the passerine species of the non-native frugivore community on O’ahu have morphologically diverged from their native ranges. We compared a variety of traits, all important for frugivory, between museum specimens from the species’ native ranges to wild individuals from O’ahu. All four species tested exhibited significant divergence ranging in magnitude from 2.3% to 13.0% difference in at least two traits. Using a method developed from quantitative genetics, we found evidence that a mixture of non-adaptive and adaptive processes worked in concert to create the observed patterns of divergence. Our results su...