Dissertation Research: The Ecological and Evolutionary Significance of Interaction Modification in Ant-phorid Interactions

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0104946 - D. Feener and Edward LeBrunThe factors that determine which species live in a particular area and the relative abundance of those species are only partially understood. Much of our knowledge is derived from studying pairs of species interacting. Indirect effects, a second category of species interactions in which one species affects a second via its interactions with a third, can also influence community structure. Parasitism of worker ants by phorid flies changes the outcome of competitive interactions between the ant species attacked by the fly and other ant species. The result of parasitism is that the species that would normally lose to the parasitized species wins. This change in the outcome of competitive interactions constitutes an indirect effect that potentially has a strong influence on the structure of the community of competing ants. Preliminary investigation has already revealed additional indirect effects relevant to this process. The proposed research, to be conducted in Southeastern Arizona, will quantify the indirect effects that parasitism by phorid flies has on the host ant and determine how the indirect effects change the outcome of interactions between competing ants. The goals are to: 1) quantify the effect of parasitism on the ability of the host ant to compete with non-parasitized species; 2) determine whether competitors benefit from food resources lost by the host as a result of parasitism; 3) test the validity of a theory predicting how strongly the outcome of competitive interactions will be modified by parasitism. This effort is important because it will provide the first detailed investigation into how strongly indirect effects that modify interactions between species effect the identity and abundance of competing groups of species. It will directly address the predictability of this impact. It will expand our understanding of how locally co-existing groups of ant species, an extremely ecologically important group, are assembled and how phorid parasitoids impact this process. Finally, it will increase our ability to predict the efficacy of using phorid flies in efforts to biologically control invasive species of ants.