68.7 Saturday, Jan. 5 Are invasive species stressful? LANGKILDE, T*; FREIDENFELDS, N.A.; THAWLEY, C.J.; ROBBINS, T.R.; GRAHAM, S.P.; Pennsylvania State University email@example.com
Invasive species represent a substantial threat to native species worldwide. Previous research has focused on population-level impacts on invasive species; however, the sub-lethal effects of invasive species on wild living vertebrates are relatively unknown. We conducted a series of laboratory and field surveys and manipulations to assess the impact of invasive red imported fire ants (Solenopsis invicta) on physiological stress levels (coticosterone, CORT) of native fence lizards (Sceloporus undulatus). Field surveys revealed that lizards from sites that had been invaded by fire ants had higher levels of CORT than did those from uninvaded sites. Direct encounters with fire ants caused increased levels of CORT in lizards, suggesting that fire ants may be directly driving the pattern observed in the field. Longer-term exposure to fire ants in field enclosures resulted in lower baseline levels of CORT as compared to controls, however. This may be due to the stress associated with enclosures, in combination with fire ant exposure, pushing lizards into chronic stress and resulting in a breakdown in negative feedback controls of the stress response. These results underscore the challenges of assigning causation to studies of anthropogenically-induced stress, and the importance of considering the length, frequency, and magnitude of exposure to the stressor when examining its consequences.