Sustainable Solutions -- University of Texas


Introductions of South American Phorids to Texas: Improving Methods of Release, Monitoring Outcomes and Assessing Impact of South American Phorids on Ant Community Interactions and Fire Ant Populations

Principal investigator:
Lawrence E. Gilbert
Section of Integrative Biology
University of Texas
Austin, TX 78712-1064

Funding Amount/2 Years: $330,856

Relevance/Implication of Project:
Biological control of the imported fire ant is the only hope for low cost and sustained suppression of this exotic species below economically and ecologically damaging thresholds. Phorid flies have great potential to be a major part of a biological solution to the fire ant problem. Understanding how best to introduce a parasitoid, how to monitor success of its establishment, and how to assess its biological control potential in the field are fundamental elements of any biocontrol attempt.

Summary of Work to be Done:
This project continues and extends experimental introductions of Pseudacteon tricuspis in Texas with baseline studies of ant communities at release and control sites. The most significant impact of Pseudacteon phorids on the imported fire ant is to shift the pest's competitive edge against native ant species by altering imported fire ant workers' foraging and defensive behaviors around food sources and nest sites. How such behavioral ecological interactions are structuring ant communities prior to and during the expansion of introduced phorid populations is an important key to interpreting the outcome of release attempts. Subprojects organized under this umbrella project involve laboratory and field experiments on how phorids influence S. invicta behavioral ecology, population biology, and community ecology. All are integrated with, and applied to, ongoing attempts to introduce phorids for biological control (subproject A). In the laboratory, we will use experimental imported fire ant colonies to measure the demographic consequences of phorid suppression of food gathering in a competitive environment (subproject D). This research will be the first to quantitatively connect foraging disruptions due to phorids to the growth rates and caste structures of colonies and will aid in developing predictive models of population level impacts in the field. Outdoors, we will extend past studies of S. invicta x S. geminata competition to include dominant natives such as Forelius (subproject C). All proposed field experiments assessing phorid impacts on fire ant native ant interactions will be conducted at selected release sites and thus will simultaneously contribute to introducing fly populations at such localities. Finally, in a greenhouse, we continue to explore for improved methods for introducing phorids into ant populations in the field (Subproject B). Such an integrated approach is motivated by a very limited supply of phorid flies, of suitable sites for release, and of manpower.