Invasion and high-elevation acclimation of the red imported fire ant (Formicidae: Solenopsis invicta) in the southern Blue Ridge escarpment region

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Amanda Jane Lafferty (Creator)
Institution
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Advisor
James Costa and Robert Warren II

Abstract: The red imported fire ant, Solenopsis invicta, is an invasive species in the United States that has rapidly spread throughout the country since its first introduction to Mobile, Alabama, in the 1930s from South America. Within the past decade, researchers have predicted elevational and latitudinal limits on S. invicta’s distribution owing to the presumed difficulty of their coping with the severity of high-elevation winters. Building on recent reports of S. invicta colonies established at elevations in excess of 1219 meters in Macon and Jackson counties, NC, I subsequently (2016-2017) documented approximately 75 live colonies in the Highlands and Cashiers areas of Macon and Jackson Counties. The presence of these invasive ants at relatively high elevations raises the question of the likelihood of their continued persistence. In this study I explored possible physiological and behavioral adaptation of S. invicta to high elevation environments through a comparison of cold and heat tolerance, fat content, and nest-site selection collected along an elevational gradient from piedmont to montane regions in the Carolinas and north Georgia (203-1228 m). For comparison, I also collected physiological temperature tolerance data for the dominant native woodland ant Aphaenogaster picea. Solenopsis invicta occurring at higher elevations exhibited a significantly greater tolerance for cold temperature extremes as compared to lower-elevation conspecifics. This tolerance differential resembles that of the native ant A. picea, which naturally occurs along a similar elevational gradient. Whereas S. invicta had a significantly higher tolerance for heat and a wider overall tolerance range compared to the native ant A. picea, both species exhibited a similar downward shift in thermal tolerances when moving up the elevational gradient. There was no significant difference in colony lipid content along the gradient, suggesting that greater metabolic rates are not needed to sustain these ants through winter dormancy at high elevations. Finally, nest-site selection in proximity to a thermal mass (rocks, logs, concrete footers, etc.) does not seem to improve thermoregulation, and ants at high elevations do not appear to select nest sites based on proximity to a potential thermal buffer. The results are discussed in the context of future projections for the continued spread of S. invicta in montane and higher-latitude regions.

Additional Information

Publication
Thesis
Language: English
Date: 2018
Keywords
Aphaenogaster, entomology, fire ant, North Carolina, Solenopsis invicta, thermal tolerance

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