My research is at the intersection of ecology and evolution; I study how the movement of species and changing environments alter evolutionary trajectories. I look at these dynamics during species' range expansions, which can both influence and instigate rapid evolution. I'm particularly interested in biological invasions and how we can use invasions to understand basic biological questions and improve conservation of native ecosystems.
The tamarisk leaf beetle, a biological control agent for tamarisk.
Tamarisk, an invasive plant in the western United States
My dissertation research uses a biological control system to answer basic evolutionary ecology questions. The tamarisk leaf beetle (Diorhabda carinulata) was introduced to the United States in 2001 to help control the invasive plant tamarisk. The beetle helps control the plant by eating its leaves. I study how the beetle is evolving during its expansion to new areas of tamarisk through spatial processes, adaptation, and hybridization. The results from my research can be used to improve predictions of other range expansions and help improve the safety and efficacy of biological control.
Two flight mills in action in the lab. Beetles are attached to the end of a thin wire and fly in circles, activating sensors as they go.
Dispersal Evolution in the Tamarisk Leaf Beetle
By using flight mills in the lab, we were able to quantify the dispersal ability of hundreds of tamarisk leaf beetles. We are using this data to understand how dispersal ability evolves during range expansions into novel environments. Theory predicts that dispersal ability should evolve upwards on range edges, but those theories often don't take into account changing environments. By using beetles from the wild, we can examine the effects of range expansion and novel environments on dispersal ability.
Diapause Timing Evolution in the Tamarisk Leaf Beetle
Diapause (like hibernation) in the tamarisk leaf beetle is triggered by shortening daylengths in the fall. As the beetles' range expands into southern latitudes, the daylengths are shorter during the summer and fall. This means the beetle needs to adjust the daylength cue that triggers diapause in order to avoid going into diapause in the summer. We defined a new trait to measure an individual's diapause propensity at particular daylengths. This trait will help us understand how the diapause cues are evolving at both individual and population scales.
Beetle collection sites for the dispersal and diapause timing studies. We are looking for divergent evolution between the core (blue) and edge (green) populations in dispersal ability and diapause timing.
Diorhabda larvae cause the most damage to tamarisk trees.
Hybridization and Host Choice
The safety of biological control relies on the introduced agent being very specific to the target species. Hybridization can increase genetic diversity, which could lead to increased evolution, including in ways that we don't want or expect. The tamarisk leaf beetle is hybridizing between three very closely related species that were introduced into the United States. While a host preference switch is unlikely, we want to make sure hybridization and increased genetic diversity isn't changing which plants the beetle prefers to eat.