Stories about invading species are a fact of modern life. Whether fire ants, zebra mussels, or Asian long horned beetles, invasive species may not immediately capture our attention; however, when they cause problems, they are impossible to miss. But new research is showing that invaders also promote changes that are harder to see but perhaps much more common. For many years, ecologists assumed that native species dealt with invaders by altering their behavior or, more simply, by moving to a new habitat. But as Tracy Langkilde shared with the F&ES community on Friday, invasive species can even cause evolutionary changes in their neighbors.
Langkilde, an
assistant professor of biology at Penn State University, made her remarks in a keynote address during the
28th Annual Doctoral Research Conference. Just eight years since earning her doctorate, Langkilde has already authored nearly 50 publications and, this summer, received the Ecological Society of America’s Mercer Award. The Mercer, the society’s highest honor for a young ecologist, was presented to her in recognition of her work on the impact of invasive fire ants on native lizards, research she began while a postdoctoral fellow at Yale.
Billions of dollars are spent each year on the management of invasive species in the United States alone, and her research focuses on ways to reduce that cost while maintaining healthy ecological systems. Langkilde noted that ecologists know very little about the long-term impact of them on native species. Fire ants (
Solenopsis invicta) act simultaneously as predators and venomous prey upon native species, including the native fence lizard (
Sceloporus undulatus).
In an odd twist, fire ants and lizards can act as predators to each other. As a victim of ant attacks, adult lizards develop anti-predator behavior and longer legs that allow them to avoid encounters and escape from attacks by fire ants. Juvenile lizards are most vulnerable to fire ants as toxic prey, because they are stung inside the mouth as they eat these invasive ants, causing them to avoid eating fire ants.
“Evolutionary and lifetime exposure to a threat can interact in complex ways to shape these adaptive responses across lifetimes,” said Langkilde. “It is therefore critical that we consider both short- and long-term impacts of invaders if we are to adequately predict and manage these threats.”
David Skelly, Associate Dean for Research at F&ES, noted, “Tracy began this work not that many years ago and has already developed a really sophisticated understanding of how the dialogue between an invader and a native species is carried out across the initial period of contact. Her work will not only help us to understand why some native species manage to make it while others succumb, it will also help us to understand the aftermath of invasions that may have taken place long ago.”
