Do epigenetic mechanisms regulate wing color patterning in painted lady butterflies?

Biologists have long been fascinated by the spectacular diversity of colors and patterns in nature. It is widely assumed that microevolutionary processes (mutation, selection, drift) are the primary drivers of biological diversity. Recently, epigenetics has emerged as an important player in phenotypic variation. Epigenetics refers to heritable changes in appearance due to changes in the DNA structure rather than the code. One of the most dramatic displays of morphological variation are the colors and patterns that decorate the wings of butterflies. Although wing color patterns are largely fixed within species for distinguishing characteristics, some species of butterflies exhibit seasonal or geographic variation known as polyphenism. Polyphenism is thought to be an epigenetic phenomenon; however, this has never been tested in butterflies. We tested this assumption by conducting experiments to examine 1) whether DNA methylation is present in wings during different larval and pupal stages when wing color patterns are developing and 2) whether rearing caterpillars on diet spiked with epigenetic modifiers, (Anacardic acid a histone acetyltransferase inhibitor and GSK-J4, a demethylase inhibitor of H3K27) alters their wing color patterns. We discuss results of these studies, including an examination of RNA expression in experimental and control groups.