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United States Department of Agriculture

Agricultural Research Service

Title: Body size, colony size, abundance, and ecological impact of exotic ants in Florida's upland ecosystems

Authors
item King, Joshua - UNIVERSITY OF FLORIDA
item Porter, Sanford

Submitted to: Evolutionary Ecology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2007
Publication Date: July 1, 2007
Citation: King, J.R., Porter, S.D. 2007. Body size, colony size, abundance, and ecological impact of exotic ants in Florida's upland ecosystems. Evolutionary Ecology Research. 9(5):757-774.

Interpretive Summary: With hundreds of invasive species established in new localities around the world, ants are an important, widely distributed, and growing group of exotic animals. The success of many established exotic ants is hypothesized to be related to competitive advantages associated with smaller workers and larger colonies. To evaluate this hypothesis, it was tested by thoroughly sampling ant communities across a range of ecosystems in north-central Florida, a region with a large group of exotic ants. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, Gainesville, Florida, the University of Florida, Nematology and Entomology Department, and Florida State Univerisity, Department of Biological Science, report that exotic ants were neither abundant nor diverse in any of the undisturbed woodland ecosystems. In open field sites, exotic ants accounted for about 40% of total ant abundance and 25% of species richness. Contrary to the predicted hypothesis, the average body size of exotic ants was not obviously different from related native species. Similarly, with the exception of imported fire ants, the average colony size of exotic ants was not larger than native species. The results of this paper are important because they show that introduced ants (including imported fire ants) were not abundant in any of the native woodland ecosystems. Consequently, exotic fire ants are not a threat to the biodiversity of native animals in Florida's wooded upland habitats.

Technical Abstract: With hundreds of species established in new localities around the world, ants are an important, widely distributed, and growing group of exotic animals. The success of many established exotic ants is hypothesized to be related to competitive advantages associated with smaller workers and larger colonies relative to co-occurring native species. To evaluate this hypothesis, ant assemblages were thoroughly sampled across the range of upland ecosystems in north-central Florida, a region with one of the most diverse exotic ant faunae in the world. Patterns of species richness, abundance, worker body size, and colony size were compared among species and ecosystems. We found that exotic ants were neither abundant nor diverse in any of the undisturbed upland ecosystems. In disturbed field sites, exotic ants accounted for about 40% of total ant abundance and 25% of species richness. A total of 94 species, including 13 exotic species and 9 endemic species, were captured. The average body size of exotic ants was not obviously different from related native species. The average colony size of exotic ants was smaller than native species, with the exception of Solenopsis invicta which had the largest colony size of all species. Introduced ants (including S. invicta) were neither speciose nor abundant in any of the native woodland ecosystems. Florida's intact, native upland ecosystems appear to be resistant to invasion of exotic ant species despite the fact that surrounding disturbed habitats host a large diversity and abundance of introduced species. The prediction that exotic species have smaller workers than related native species was not supported.

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