Stinging vs. feeding: Immune effects of invasive fire ants on a native lizard species

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Catherine Tylan, Biology, Pennsylvania State University, University Park, PA and Tracy Langkilde, Department of Biology, The Pennsylvania State University, University Park, PA

Background/Question/Methods
Native ecosystems have been exposed to invasive species for decades, and the spread of non-native species is likely to continue into the future. Therefore, it is important to understand the effects invasive species have on the animals in ecosystems into which they have been introduced. We address this question using the eastern fence lizard (Sceloporus undulatus), which has been exposed to invasive stinging fire ants (Solenopsis invicta) for over 70 years. The presence of these invasive, predatory ants is associated with differences in native fence lizards, including to their immune functions, as compared to lizards from ecologically similar sites which are not yet invaded by fire ants. We sought to discover if these documented immune differences are directly stimulated by exposure to fire ant venom through stinging or consumption of ants by lizards that are naïve to fire ants.
Results/Conclusions
We measured a broad array of immune responses and found that being stung by fire ants increased some lizard immune responses and decreased others. In contrast, fire ant consumption increased lizard immune responses that were decreased when the lizards were stung; no responses were decreased as a result of fire ant consumption. These results may indicate that consumption of fire ants can bolster immune responses needed to combat later envenomation through stinging.