Skip to main content
ARS Home » Research » Publications at this Location » Publication #201870
Title: Ecological dominance of the red imported fire ant, Solenopsis invicta, in its native range

Author
item CALCATERRA, LUIS - USDA/ARS/SABCL
item LIVORE, JUAN - UNIV OF BUENOS AIRES
item DELGADO, ALICIA - UNIV OF CORDOBA
item BRIANO, JUAN - USDA/ARS/SABCL

Submitted to: Acta Oecologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 3/1/2008
Citation: Calcaterra, L.A., Livore, J.P., Delgado, A., Briano, J.A. 2008. Ecological dominance of the red imported fire ant, Solenopsis invicta, in its native range. Acta Oecologica. p. 411-421.

Interpretive Summary: Although some ants may not be particularly dominant in their homeland where they coexist with co-evolved competitors, parasites, pathogens, and predators, they often eliminate competitors when they are introduced into new ranges. Most studies have been dedicated to describing the impact of particular invasive ant species on native ant communities in its introduced range. However, few studies focus on invasive species in their native range to understand the causes of the invasion success. This work examines the interaction of the red imported fire ant with the most common above-ground (terrestrial) foraging ants in northeastern Argentina. The factors that allow the red imported fire ant to coexist with other omnivorous ants were studied in a simple and a complex habitat in the Corrientes province. This study shows that the red imported fire ant was the most dominant species of the assemblage. Its success was based on (1) the high number of individuals, (2) the well developed recruitment system of workers, (3) the aggressive behavior (Sting and bite), and (4) the uninterrupted foraging activity. Contrarily, the red imported fire ant showed a relative low ability to discover baits despite being very abundant. Differentiation in discovery and dominance of food resources would be the most important mechanism that allowed other omnivorous ants to coexist with the red imported fire ant in its native land. The presence of phorid flies decreased the foraging rates of the red imported fire ants but not enough to interfere in the interactions with competitor ants.

Technical Abstract: Despite the widespread impacts invasive species can have in introduced populations, little is know about patterns of co-existence between invaders and similar taxa in their native range. This study examines interactions between the red imported fire ant, Solenopsis invicta Buren, 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 phorids flies on the interactions between S. invicta and the other ant species. Twenty-eight ant species coexisted with S. invicta in a gallery forest gap, whereas only 10 in a xerophytic forest grassland. The red imported fire ant was similarly active during day and night. In spite of its apparent poor exploitative performance, S. invicta showed the highest ecological dominance and the second behavioral dominance after Camponotus blandus (Smith). Solenopsis invicta won 78% of the interactions with other ants, mostly against its most frequent competitor, Pheidole cf. obscurithorax Naves, dominating baits via mass recruitment and chemical aggression. Red imported fire ants won 80% of the scarce interactions with Linepithema humile (Mayr). Most of S. invicta´s competitors were abundant, likely because they were faster discovering baits. Crematogaster quadriformis Forel was the fastest forager and the only ant that won equal number of contests against S. invicta. Phorid flies affected the foraging rate of S. invicta, but not the outcome of interspecific interactions. Complexity of habitat apparently promoted rich ant assemblages with species in similar microhabitats by minimizing agonistic interactions via differentiation in patterns and strategies of resource discovery and dominance.