Ordination Analysis of Ant Faunae along the Range Expansion Front of the Red Imported Fire Ant in South-Central Texas

Abstract

The red imported fire ant (RIFA), Solenopsis invicte, is expanding its range into western Texas. Although few native ant species have been found to be either directly or indirectly competitive with the RIFA, collectively or individually native species may offer some resistance, resulting in a decrease in the rate of RIFA infestation. The objective of the present study was to characterize the predominant ant species at the westernmost edge of RIFA infestation and to determine through niche overlap which native ants may be in competition with the RIFA.
Ants from four habitats (juniper, oak, cypress, and pasture) were sampled monthly with pitfall traps in Kerr and Bandera Counties, Texas, for one year. A total of 27,683 individuals representing five subfamilies and at least 37 species was collected. The most commonly collected ants from all habitats were Solenopsis invicte (RIFA), Solenosis geminata, Pheidole spp., Monomorium minimum, Foreius pruinosus, and Paratrechina terricole.
Data analysis by Wisconsin/polar ordination distinctly separates the several habitats in space through time (seasons); whereas, quartile analysis of the prominant ant spe-cies emphasizes habitat-season interactions. Factor gradients that determine species prominance within and among habitats are strongly indicated. However, our data indicate that native species may offer only little resistance to the RIFA.