UCB Moorea Class: Biology and Geomorphology of Tropical Islands

 The role of mutualisms among invasive species in facilitating invasions remains relatively unexplored. Yet such interactions have high potential to alter intact community composition and function due to their positive fitness effects on the species involved. The following study explores an interaction that evolved independently among naturalized hibiscus and invasive ants and Hemiptera that colonized the island of Mo’orea, French Polynesia centuries apart.  For this study, a geographic survey was conducted across 7 plots, which revealed the relationship to be present across a broad range of habitats. Manipulative field experiments were also ran in order to classify the association as a mutualism, parasitism or commensalism. These experiments quantified changes in abundances and behaviors of ants and Hemiptera in response to different availabilities of sugar resources to ants. Results from these field experiments support the hypothesis that the relationship is indeed a mutualism, where all players receive a net benefit from their association with one another. The resultant finding that this is a geographically widespread mutualism among invasive species contributes to the study of invasion meltdowns. The discovery of the success of this invader-invader mutualism in an intact ecosystem contributes to a growing body of research on the role of synergistic effects of multiple species invasions in invasion meltdowns.