Phorid fly parasitoids of invasive fire ants indirectly improve the competitive ability of a native ant
2004
Mehdiabadi, N.J. | Kawazoe, E.A. | Gilbert, L.E.
1. The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species of south-eastern U.S.A. Since its introduction from South America approximately 70 years ago, this pest has devastated natural biodiversity. 2. Due to such ecological costs, Pseudacteon phorid fly parasitoids (Diptera: Phoridae) from South America are being introduced into the U.S.A. as a potential biological control agent. Here, the indirect effects of these specialised parasitoids on an interspecific native ant competitor, Forelius mccooki (Hymenoptera: Formicidae), are evaluated. 3. Over the course of a 50-day laboratory experiment, the results show that the native ant improved aspects of exploitative, but not interference, competition when S. invicta-attacking flies were present compared with when they were absent. 4. Forelius mccooki colonies from the phorid treatment had approximately twice as many foragers at food baits relative to controls; however, there was no significant difference in interference aspects of competition or native ant colony growth between the two treatments. 5. These results suggest that the S. invicta-specialised parasitoids help shift the competitive balance more in favour of F. mccooki than if these flies were not present; however, this competitive advantage does not translate into increased colony growth after 50 days. These laboratory findings are interpreted with regard to the more complex interactions in the field.
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