Determining the Evolutionary Forces responsible for Toxin Resistance in Milkweed Butterflies
This project aims to determine whether or not bottom-up evolutionary forces such as the enhanced ability to feed on toxic plants are responsible for the evolution of toxin resistance in milkweed feeding butterflies. This hypothesis favoring bottom-up evolutionary forces is contrary to that favoring top-down evolutionary forces such as enhanced protection from predators through the sequestration of ingested toxins. To study this question, we are utilizing CRISPR-engineered Drosophila flies that contain three key amino acid substitutions in their sodium pump. These engineered mutations correspond to mutations found naturally in milkweed butterflies. We will use a suite of experiments to address this question, including sodium pump assays, HPLC analysis of toxins in the milkweed plants, and feeding experiments with diets containing milkweeds with differing levels of toxicity.