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United States Department of Agriculture

Agricultural Research Service

Title: Positive Association Between Densities of the Red Imported Fire Ant, Solenopsis Invicta (Hymenoptera: Formicidae) and Generalized Ant and Arthropod Diversity

Authors
item Morrison, Lloyd
item Porter, Sanford

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 18, 2002
Publication Date: July 17, 2003
Citation: MORRISON, L.W., PORTER, S.D. POSITIVE ASSOCIATION BETWEEN DENSITIES OF THE RED IMPORTED FIRE ANT, SOLENOPSIS INVICTA (HYMENOPTERA: FORMICIDAE) AND GENERALIZED ANT AND ARTHROPOD DIVERSITY. ENVIRONMENTAL ENTOMOLOGY. 2003. v. 32(3). p. 548-554

Interpretive Summary: The red imported fire ant, Solenopsis invicta, is a threat to native insect diversity. After S. invicta invades an area, overall insect diversities usually decline. Few studies, however, have compared areas with naturally varying densities of S. invicta. Those that have found negative associations between S. invicta density and native ant species diversity. Scientists working at the USDA-ARS, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, compared areas with naturally varying densities of S. invicta and examined the association of S. invicta density with three measures of overall insect diversity. Surprisingly, moderate positive correlations between S. invicta density and species richness of both ants and non-ant insects were found. These results indicate that S. invicta is not the most important factor regulating overall insect species diversity and suggest that S. invicta densities, as well as diversities of other ants and insects, may be regulated by common factor(s). Many invaded communities may be more resistant to S. invicta than generally believed, or possess an unexpected resilience for recovery if S. invicta can be permanently suppressed.

Technical Abstract: The invasive ant, Solenopsis invicta Buren, is a threat to native arthropod biodiversity. We compared areas with naturally varying densities of mostly monogyne S. invicta and examined the association of S. invicta density with three diversity variables: (1) the species richness of ants, (2) the species richness of non-ant arthropods, and (3) the abundance of non-S. invicta ants. Pitfall traps were used to quantify S. invicta density and the three diversity variables; measurement of mound areas provided a complementary measure of S. invicta density. We sampled 45 sites of similar habitat in north central Florida in both the spring and autumn of 2000. We used partial correlations to elucidate the association between S. invicta density and the three diversity variables, controlling for the effects of temperature and humidity on foraging activity. Surprisingly, we found moderate positive correlations between S. invicta density and species richness of both ants and non-ant arthropods. Weaker, but usually positive, correlations were found between S. invicta density and the abundance of non-S. invicta ants. A total of 37 ant species, representing 16 genera, were found to coexist with S. invicta over the 45 sites. These results indicate that S. invicta densities at our monogyne sites were not the most important factor regulating diversities of ants and other arthropods in the communities sampled, and suggest that S. invicta densities, as well as diversities of other ants and arthropods, are regulated by common factor(s) (e.g., productivity). Many invaded communities may be more resistant to S. invicta than generally believed, or possess an unexpected resilience for recovery if S. invicta can be permanently suppressed.

Last Modified: 10/30/2014
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