Rapid morphological change of nonnative frugivores on the Hawaiian island of O'ahu*

Abstract

Novel ecosystems have become widespread created, in part, by the global spread of species. The nonnative species in these environments can be under intense evolutionary pressures that cause rapid morphological change, which can then influence species interactions. In Hawaii, much of the native frugivore community is extinct, replaced by nonnative bird species. Here, we determined if the passerine species of the nonnative 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 nonadaptive and adaptive processes worked in concert to create the observed patterns of divergence. Our results suggest that rapid morphological change is occurring and, based on the traits measured, that these changes may influence seed dispersal effectiveness. As these species are largely responsible for seed dispersal on the island, the rapid morphological change of these species can influence the stability and maintenance of plant communities on O'ahu.

Diet, feeding behavior, and jaw architecture of Taï monkeys: Congruence and chaos in the realm of functional morphology

“…This raises two different, but important, possibilities for focusing future research designs. The first is that morphological evolution may proceed very rapidly given an ecological shift . The second is that natural populations may not be exploiting the full range of latent phenotypic plasticity available to them.…”

Digest: How do nonnative frugivorous birds adapt to life in O'ahu?*

“…In this study, Gleditsch and Sperry () characterized morphological adaptations of the four most common fruit‐eating bird species on O'ahu by measuring features such as tail length, wing chord, tarsus length, and bill size. The researchers caught wild birds in O'ahu, measured them, and compared those measurements to those taken from museum specimens from populations in each species’ native range.…”

“…Flowchart depicting experimental methods used in Gleditsch and Sperry (). Two types of samples were used in this research: four species of wild‐caught birds from O'ahu and museum specimens of the native populations of the same bird species.…”

“…Gleditsch and Sperry's () work helps elucidate mechanisms that allow invasive species to adapt to novel environments and vice versa. Species with traits suited to the new environment, such as short generation time or the ability to tolerate a wide range of environmental temperatures, are generally more effective invaders (Sakai et al.…”

“…In this study, Gleditsch and Sperry (2019) in each species' native range. The researchers were careful to control for measurement error and size differences between the populations attributable to comparing live birds to museum specimens ( Fig.…”