The red imported fire ant (Solenopsis invicta) invasion and its impact on ant communities in northeastern Mexico

The red imported fire ant, Solenopsis invicta is established in at least several hundred hectares in Matamoros, northeastern Mexico, adjacent to infestations in Texas. We investigated components and densities of ant communities in habitats with different densities of S. invicta. We used pitfall traps to sample ants at three sites. Sites 1 and 2 include zones with different densities of S. invicta. Site 3 included infested and uninfested areas, in both natural and agricultural settings. For analysis we used Analysis of Variance, correlation, and multivariate (factor and cluster) analysis. S. invicta individuals comprised 30-48% of all collected ants. S. invicta was negatively correlated with the more common local ants. At site 3, local ants were significantly less abundant where S. invicta was present. Multivariate analysis indicated a significant association with Forelius mccooki, native Solenopsis spp. and Monomorium minimum. The abundance of S. invicta and the general similarity of our assemblages and numerical data with those of “older” fire ant infestations in the USA, suggest that S. invicta has been present in parts of this area for a long time (several years?).