Document: KIR-3-52-58

Factors limiting the red imported fire ant, Solenopsis wagneri in its native range in Brazil.

WACKFORD, K.M.* and D.H.FEENER, JR.

University of Utah, Salt Lake City, UT 84112-0840, USA. ¹

Abstract:
Invasive species which assume dominant, destructive roles in their new communities are often much less dominant in their native ranges. In many cases, invasive species are successful in new locales because they have left behind key competitors, predators, pathogens, or parasites. Although the Red Imported Fire Ant Solenopsis wagneri has been a major pest invader in the US for over fifty years, to date no studies have comprehensively examined its ecological interactions in its native range in Brazil. In Brazil, the fire ant is a dominant competitor, and may be the most dominant ant in its preferred habitat of short grass. However, it does not achieve the levels of monodominance that it does in the U.S. Instead, it shares both short and tall grass habitats with at least twenty other species of directly competing ants. In a four-year study, we examined three interacting factors that limit the fire ant in its native range: Competition, flooding, and parasitoids. The ants Camponotus rufipes and Paratrechina fulva are superior competitors to the fire ant, but prefer less-flooded locations with taller grass. Seasonal flooding forces the movement of fire ant nests and intensifies competition between fire ants and superior ants by forcing them to occupy the same tall grass habitats for part of the year. Flooding may also favor competitively inferior ants that can colonize short grass areas after floods more rapidly than fire ants. The presence of multiple species of species-specific phorid parasitoids restricts the foraging of fire ants and decreases their competitive ability. Here we evaluate of the importance of competitive superiors, flooding, and parasitoids to the limitation of the fire ant in its native range.

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This abstract is being presented at: 4:45 PM in session:
Oral Session #53: Terrestrial Invertebrate Ecology.