PS 11-156 - The coexistence of invasive ants through trait-mediated indirect effects by Pseudacteon spp. on Puerto Rican coffee farms

Abstract: In agroecosystems, novel ecological networks occur as a result of direct human interaction bringing together species that haven’t historically occurred together and introducing new competitors for several species. Within these novel interaction networks, predators can influence prey behavior through trait-mediated indirect effects (TMIE), effectively altering the way a prey forages and interacts with competitors. In this study, we consider TMIE by phorid flies (Pseudacteon spp.) as a method of coexistence between two invasive ants (Solenopsis invicta and Wasmannia auropunctata) competing on Puerto Rican coffee farms. Within these farms, W. auropunctata is the most dominant ant, while S. invicta is the second most dominant, despite S.invicta being behaviorally more aggressive and a stronger competitor. Phorid flies are parasitoids that specialize on S. invicta, limiting their competitive abilities in their native ranges. In this study, we compare a W. auropunctata-dominated farm and a S. invicta-dominated farm through disturbance and foraging surveys of S. invicta, assessing phorid activity and density, as well as factors that may be influencing the two. We find that the farm experiencing W. auropunctata dominance has a higher count and attack rate of phorid flies in comparison to the farm experiencing S. invicta dominance These results indicate that phorid fly activity and density can contribute to trait-mediated indirect effects (TMIE) on S. invicta, allowing them to coexist with the rest of the ant community on Puerto Rican coffee farms.