Integration of an Invasive Plant in Hummingbird and Flower Mite Networks Is Driven by Ecological Fitting and Generalization

Abstract

Most plant communities worldwide include exotic plants, which did not evolve with local organisms. The central goal of this study is to test if native organisms expanding their interactions to novel hosts are usually generalists or specialists. Here we studied new associations between hummingbirds, flower mites and Musa velutina (Musaceae), an exotic plant native to northeast India currently invading lowland forests in Costa Rica. Hummingbirds are pollinators, but flower mites feed on nectar without contributing to pollen transfer. Flower mites hitch rides on hummingbird beaks to colonize new flowers. To determine the original diet breadth of hummingbird and flower mite species, we assembled hummingbird and flower mite interactions at La Selva Biological Station. We identified four hummingbird species visiting Musa velutina. DNA barcode analyses identified only one species of flower mite colonizing flowers of M. velutina. All new associations with M. velutina involved generalist hummingbird and flower mite species. Musa velutina displays both male and female flowers. Although flowers of both sexes were equally visited by hummingbirds, mites were 15 times more abundant in male than in female flowers. We hypothesize that this is the result of constant immigration coupled with mite population growth. Only half of the mites hitching rides on hummingbird beaks emigrate to newly opened flowers. Our results show that M. velutina integration to a plant community occurs mainly by establishing interactions with generalists.