The effect of pasture management on fire ant, Solenopsis invicta (Hymenoptera: Formicidae), abundance and the relationship to arthropod community diversity

The red imported fire ant, Solenopsis invicta, is one of the most prolific invasive species to the Southeastern U.S. These invaders preferentially colonize highly disturbed land and grassland habitat. Management of livestock in pasture systems can have a profound impact on the level of disturbance in grassland habitats, and we hypothesized that pasture management would have a significant effect on S. invicta abundance in the Southeastern U.S., and arthropod diversity would negatively correlate with this invasive species. We studied the effects that pasture management systems (based on stocking density, rotation frequency, and insecticide application rates) have on fire ant mound abundance and arthropod diversity for the soil, foliar, and dung communities. S. invicta mounds were quantified and mound areas were documented along transect lines in six pastures. Soil and foliar arthropod communities were collected along the same transect lines, and dung communities sampled from pats within the pasture system. Pastures managed under adaptive multi-paddock (AMP) practices had 3.35x more S. invicta mounds and 4.64x more mound area than their conventionally managed counterparts. However, arthropod diversity did not correlate with S. invicta abundance for any of the three arthropod communities sampled. This study shows pasture management can have a significant impact on S. invicta mound abundance, but arthropod communities in AMP managed pastures did not suffer decreased diversity from increased abundance of S. invicta. Additionally, this study demonstrates that this invasive species does not necessarily contribute to diversity decline, at least under AMP pasture systems.