Meeting Abstract
Following exposure to stressors, energy resources are reallocated towards immediate responses, which can divert energy from functions such as the immune system. Which systems are suppressed may be altered by an animal’s evolutionary history. The eastern fence lizard (Sceloporus undulatus) is a native species impacted by the predatory invasive fire ant (Solenopsis invicta). We examined how history of invasion and acute stress treatment affected the cell-mediated immune response of post-gravid lizards. Lizards were captured from sites with long (>70 years) histories of fire ant invasion, and correspondingly higher levels of corticosterone, or those not yet invaded by these ants. All lizards were treated while gravid with either a physiologically relevant dose of the stress-relevant hormone, corticosterone, to simulate the corticosterone response to a fire ant attack, or a vehicle control. We measured the cell-mediated immune response of females post-laying with the phytohemagglutinin skin test. We found that history of exposure to stress (associated with fire ant invasion) and the contemporary stress treatment affect cell-mediated immune response. Lizards treated with corticosterone had reduced immune response compared to controls, and lizards from high-stress fire ant invaded sites had reduced immune response compared to those from low-stress uninvaded sites. These results suggest that the fire ant-induced stress may be immunosuppressing lizards. Future work on how different branches of the immune system respond to environmentally-induced stressors will be informative for predicting and managing these threats.
