The effect of the red imported fire ant, Solenopsis invicta, on components of plant fitness and structure of the arthropod community in coastal prairie on the Upper Coast of Texas

Previous studies have shown that insects are an important part of the diet of fire ants, Solenopsis invicta. Since this is the case, fire ants could include in their diet significant numbers of herbivorous insects and, by reducing the number of herbivorous insects in a habitat, could positively affect the fitness of plants in that same habitat. No empirical studies have been done that compare the number of herbivorous insects and fitness of plants in areas with naturally occurring numbers of fire ants and areas with fire ants artificially reduced. The goal of this research was to determine the effect of fire ants on herbivorous insect populations and the indirect effect of fire ants on plant fitness. Plots with high-ant density (naturally occurring numbers of fire ants) and plots with low-ant density (artificially produced with Logic{dollar}spcircler{dollar}) were maintained for two years at the University of Houston Coastal Center near LaMarque, in Galveston County, Texas. Fire ant numbers, arthropod densities, and data for components of fitness for Rudbeckia hirta were collected from February to November of 1992 and 1993. Plots with low-ant density and plots with high-ant density were not significantly different from each other either year for their overall arthropod composition by MANOVA. After Bonferroni correction for multiple comparisons, ANOVAs also indicated no significant differences for individual arthropod groups. Rudbeckia hirta did better in plots with high-ant density for 1992, but there was little difference between plots with low-ant density and plots with high-ant density in 1993. During and after a very dry July, a different ant, Paratrichina terricola, took the place of the fire ant, Solenopsis invicta, in low-ant density plots in 1993.