Invasive Species

Invasive species are a serious concern for ecologists as they are one of the leading reasons that native species may become endangered or extinct. Invasive species, such as kudzu, cane toads in Australia, Burmese pythons in the Everglades of Florida, and those pesky stink bugs can all cause serious trouble for species that have not evolved with them and may be unable to cope with them. Understanding how invaders affect native species and how species can adapt to invaders is of importance for conservation reasons, but also helps us understand the ways in which species can adapt to our rapidly changing world.

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An eastern fence lizard faced with invasive fire ants.

My doctoral research in Tracy Langkilde’s lab focused on understanding how the Eastern fence lizard (Sceloporus undulatus) is impacted by and adapts to invasive red imported fire ants (Solenopsis invicta). Since the 1930’s, fire ants have spread through the southeastern U.S. (and other places). Because of their large colonies and potent venom, they defend their mounds vigorously and can paralyze and consume much larger organisms…like fence lizards! Since fire ants invaded, fence lizards have altered their anti-predator behaviors to twitch and flee more to remove and escape from these ants, and have altered stress levels and longer hindlimbs to make these behaviors more effective.

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A fence lizard twitches to remove attacking fire ants.

My research showed that, while fence lizards do use more effective antipredator behaviors to escape fire ants, they increase these behaviors when interacting with native ants too…ants that should be their prey! Doing all these dramatic twitch behaviors also seems to attract attention from other predators; as a result lizards from areas with fire ants have more injuries. In work begun with undergraduate Jill Newman, I demonstrated that fence lizard eggs are also vulnerable to predation by fire ants, suggesting that this invader imposes differing levels of natural selection on different life stages of native species.  

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To test how widespread and strong the impacts of this invader can be, I worked with undergraduate Mark Goldy-Brown (now in the Peace Corps!) to conduct a field study across the range of the eastern fence lizard to assess how fire ants impacted latitudinal clines in behavior, stress, and hindlimb length. We found that the presence of fire ants altered pre-existing clines in these traits, in some cases reversing them entirely, suggesting that invasive species can alter large scale patterns of traits over short time scales. This work is currently in submission, so stay tuned!

My other work in this system has resulted in determining the epigenetic impacts of fire ants and research led by undergraduate Mark Herr looking at how fence lizards come to eat more fire ants over multiple temporal scales.