Investigation of the potential for Red Imported Fire Ant (Solenopsis invicta) impacts on rare karst invertebrates at Fort Hood, Texas: a field study


Publication Date

January 2003


This report presents the results of a study of Solenopsis invicta, the Red Imported Fire Ant (RIFA) foraging above ground near cave entrances and inside caves at Fort Hood, Texas, and examines ways in which RIFA interacts with other organisms above ground and with cave-adapted organisms below ground. Above-ground RIFA foraging intensity was found to be related to disturbance, and high numbers of foraging RIFA were correlated with low numbers of native ants. In-cave RIFA foraging was primarily limited to the entrance and twilight zones of caves with significant RIFA densities on the surface. Occasional foraging in more remote parts of caves occurred in cooler months and RIFA gained access to the cave without using the entrance apparent to humans. RIFA foraging in the entrance and twilight zones resulted in relatively little interaction with cave-limited species, but RIFA co-occurance with important species, especially the cave cricket Ceuthophilus secretus, that utilize both cave and surface habitats indicates that there are important secondary effects which have a negative impact on the cave-limited species of concern. Keystone taxa in the cave community appear to be the cave cricket, Ceuthophilus secretus, and white (cave-adapted) springtails. At baits placed above ground at night, cave crickets often arrived at the food resource before RIFA, but the arrival and subsequent recruitment of workers by RIFA corresponded to the departure, or decline in numbers, of foraging cave crickets, indicating competition for crickets and RIFA for at least some food resources. Crickets marked at the entrance of one cave were detected up to 105 m from the cave entrance, and the trend of our data suggests that some individuals may forage even farther from the cave. Adjusting for search effort and available area at differing distances from the cave entrance, about half of the crickets forage at less than 40 m from the cave entrance, and 90% percent of the crickets forage at less than 80 m from the cave entrance.





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