Ecological dominance of the red imported fire ant, Solenopsis invicta, in its native range

Abstract

Despite the widespread impacts invasive species can have in introduced populations, little is known about competitive mechanisms and dominance hierarchies between invaders and similar taxa in their native range. This study examines interactions between the red imported fire ant, Solenopsis invicta, and other above-ground foraging ants in two habitats in northeastern Argentina. A combination of pitfall traps and baits was used to characterize the ant communities, their dominance relationships, and to evaluate the effect of phorid flies on the interactions. Twenty-eight ant species coexisted with S. invicta in a gallery forest gap, whereas only ten coexisted with S. invicta in a xerophytic forest grassland. S. invicta was the most numerically dominant species in the richest and complex habitat (gallery forest); however it performed better as discoverer and dominator in the simpler habitat. S. invicta was active during day and night. In spite of its poor capacity to discover resources, S. invicta showed the highest ecological dominance and the second-best behavioral dominance after Camponotus blandus. S. invicta won 78% of the interactions with other ants, mostly against its most frequent competitor, Pheidole cf. obscurithorax, dominating baits via mass recruitment and chemical aggression. P. cf. obscurithorax was the best food discoverer. S. invicta won 80% of the scarce interactions with Linepithema humile. Crematogaster quadriformis was one of the fastest foragers and the only ant that won an equal number of contests against S. invicta. The low presence of phorid flies affected the foraging rate of S. invicta, but not the outcome of interspecific interactions. This study revealed that the red imported fire ant ecologically dominated other terrestrial ants in its native range; however, other species were able to be numerically dominant or co-dominant in its presence.

Habitat and Grazing Influence on Terrestrial Ants in Subtropical Grasslands and Savannas of Argentina

“…This contrast is consistent with Porter et al (1992Porter et al ( , 1997 who reported that densities of Þre ants in South America average 1/5Ð1/10 of those in the United States. This difference has been mainly explained by the presence of natural enemies and/or a more intense competitive pressure in South America compared with the United States , LeBrun et al 2007, Calcaterra et al 2008.…”

“…Dominant Dolichoderinae (active and dominant ants) was not recorded in this study. Ant species were assigned to these groups based upon habitat and strata occurrence, presence, abundance, and behavior observed at baits; also, other works conducted mainly in South America on these and similar species with known natural history were considered (Kusnezov 1978;Bestelmeyer and Wiens 1996;Andersen 1997;Silvestre et al 2003;Andersen et al 2007;Calcaterra et al 2008Calcaterra et al , 2010Hill et al 2008;van Ingen et al 2008;Cuezzo and González Campero 2010). A two-way ANOVA was used to examine the inßuence of habitat type, grazing history, and their interaction on the number of functional groups (square-root ϩ 0.5 transformed) and the number of species (square-root ϩ 0.5 transformed) in each functional group.…”

Insects had it first: surfactants as a defence against predators

“…This was observed when placing caterpillars in the foraging arena close to the nest of S. invicta, and might be a realistic outcome in the field. Solenopsis invicta is known to be less efficient in discovering food than other ant species but can compensate by fast recruitment of many nest-mates (Calcaterra et al 2008). Caterpillar size in relation to predator size also plays an important role as larger caterpillars produce a lot more OS.…”

Geographical transition zone of Solenopsis fire ants (Hymenoptera: Formicidae) and Pseudacteon fly parasitoids (Diptera: Phoridae) in the state of São Paulo, Brazil

“…The distribution of parasitoid flies seems to be determined by host specificity, while fire ants distribution seems to result from climatic influence. However, data on change of niche of Pseudacteon (Pesquero 1997) and dominance of Solenopsis (Calcaterra et al 2008) indicate that interespecific competition must also be taken into consideration in the inquiry of this phenomenon.…”