Online

Brevik, Kristian

Plant and Soil Science

2020

Ph. D.

Within agricultural ecosystems, humans and insects enter into complex relationships. Humans consider many of these insects to be pests, and exert significant pressures upon them, such as efforts to kill them using insecticides. One of the ways insects respond to these efforts is by rapidly evolving resistance to insecticides - but how they do this is not fully understood. DNA methylation, an epigenetic mechanism, and transposable elements, which are mobile genetic elements within genomes, may each play a role in shaping the way insects rapidly evolve in response to exposure to insecticides. Understanding the role of transposable elements and DNA methylation in the evolution of insects who live within agroecosystems can cast light on fundamental mechanisms of evolution while informing how we might live in better relation with these species. These four chapters together provide support for complex interactions between insecticide exposure, transposable element activity, epigenetic inheritance, and adaptation to human-dominated agricultural landscapes in insects. First, I provide an overview of how insecticide-induced epigenetic effects can be inherited and may drive the evolution of resistance via epigenetic processes, contributing to ecological success in agroecosystems. Next, I utilize a large dataset of reports of insecticide resistance to determine if insect species evolve at different rates using survival analysis methodology. I then explore the diversity of transposable elements found within different populations of the Colorado Potato Beetle, Leptinotarsa decemlineata, to determine if these genetic elements play a role in the evolution of traits associated with living in agroecosystems. Finally, I analyze how DNA methylation in the Colorado Potato Beetle may be affected by exposure to insecticide, and if these changes to DNA methylation patterns are heritable and associated with genes known to be involved in insecticide resistance.