Red imported fire ant impacts on the endangered Florida grasshopper sparrow

Allen, C.R. and Forys, E.A. and Wojcik, D.P. (1997) Red imported fire ant impacts on the endangered Florida grasshopper sparrow. Gainesville, FL, Universityof Florida, Florida Cooperative Fish and Wildlife Research Unit,

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Abstract

Red imported fire ants (Solenopsis invicta) invaded peninsular Florida more than 30 years ago. Highlands and Polk counties, Florida, were probably first invaded in the late 1960s. Since then, fire ants have continued both to spread and to increase in abundance. Experimental evidence has shown that red imported fire ants may have a detrimental impact on native species, both invertebrate and vertebrate, and that these impacts may be both direct and indirect. This segment of research was designed to determine if fire ants have a negative impact on Florida grasshopper sparrow (Ammodramus savannarumfloridanus) populations at Avon Park Air Force Bombing Range, Florida. The sampling reported herein was conducted during June and October, 1997, and all analyses are restricted to data collected during those periods. As assessed by baits, fire ants were dominant on about half the sites, and absent from others. In particular, OQ Range sites tended to have fewer fire ants present, while Delta Trail sites were more heavily infested, although there were exceptions. June fire ant abundance was strongly negatively correlated with both native ant abundance (r = -0.743, P = 0.006) and native ant species richness (r = -0.730, P = 0.007). October fire ant abundance was strongly negatively correlated with both native ant abundance (r = -0.690, P = 0.013) and native ant species richness (r = -0.736, P = 0.006). The patterns of fire ant abundance as assessed by pitfalls were very similar to those determined from bait sampling. June fire ant abundance was negatively correlated (p < 0.05) with native ant richness, but other June comparisons were not statistically significant (P > 0.05). October fire ant abundance was negatively correlated (P < 0.05) with native ant richness and abundance, but other comparisons were not statistically significant (P > 0.05). There was no significant correlation between overall insect biomass as assessed by light traps and fire ant abundance as assessed by baits or pitfalls. Total biomass varied considerably among the two sample periods because of changes in overall insect abundance during different seasons. There was a negative spatial correspondence between fire ants and native invertebrates. Over most of the intensive study areas, there was a negative spatial relationship between fire ants and the abundance of native invertebrates. Over about 50% of the intensive study areas, there was a negative spatial relationship between fire ants and the abundance of Florida grasshopper sparrows, although the relationship was not as strong as that between fire ants and native invertebrates. Fire ant and native invertebrates were negatively correlated at grasshopper sparrow count locations (r =0.347, P = 0.03). A multiple regression model was fit to the data, using fire ants and native invertebrates as independent variables, and grasshopper sparrow 100-m population estimates (n = 39) as the dependent variable. The influence of fire ants on grasshopper sparrows was negative while the influence of native invertebrates was positive. However, the overall model, while suggestive, was not significant (r = 0.304, P = 0.17). Fire ant abundance was a better (negative) predictor of sparrow populations (P = 0.13) than was invertebrate abundance (P = 0.59). The overall model and influence of fire ants on sparrow populations was suggestive of a negative influence warranting analyses of data for 1998 and 1999. (Document has 93 pages)

Item Type: Monograph or Serial Issue
Title: Red imported fire ant impacts on the endangered Florida grasshopper sparrow
Personal Creator/Author:
CreatorsEmail
Allen, C.R.
Forys, E.A.
Wojcik, D.P.
Date: 1997
Publisher: Universityof Florida, Florida Cooperative Fish and Wildlife Research Unit
Place of Publication: Gainesville, FL
Projects: Research Work Order no. 175
Department: Wildlife Ecology and Conservation
Institution: University of Florida
Issuing Agency: Florida Cooperative Fish and Wildlife Research Unit
Additional Information: Final report.
Uncontrolled Keywords: red imported fire ants; fire ants; vertebrates; grasshopper sparrow; Florida; Solenopsis invicta; Ammodramus savannarumfloridanus
Subjects: Ecology
Conservation
Biology
Environment
Item ID: 939
Depositing User: Tisha Stockton
Date Deposited: 31 Mar 2008 16:49
Last Modified: 14 Dec 2010 15:59
URI: http://aquaticcommons.org/id/eprint/939

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