Functional traits of avian frugivores have shifted following species extinction and introduction in the Hawaiian Islands

The extinction and introduction of species can alter ecological processes owing to the loss or gain of species roles. In vertebrate-dependent seed dispersal, mutualisms between frugivores and fruiting plants depend, in part, on matching of functional traits. High species turnover of frugivores has occurred on the Hawaiian Islands, owing to both the loss of native frugivores and the introduction of a new suite of frugivores. How this turnover has altered the functional traits of frugivores and the potential impacts on seed dispersal remain unclear.

We investigated how avian frugivore traits differed between historic and modern assemblages of the Hawaiian Islands. We also tested how traits shifted within foraging guilds (ground versus arboreal) to distinguish potential impacts on plants within low versus high forest strata.

Compared to historic frugivores, the modern assemblage is smaller in gape width and body mass in both ground and arboreal guilds. Wing shape did not significantl...