Phylogenetics of Bagworm Moths: A Model System for Studying the Evolutionary Genetics of Sexual Dimorphism

University Of Florida, Gainesville FL

Investigators

Abstract

Almost all organisms have separate male and female sexes, but this common dynamic holds a contradiction: males and females are physiologically different from each other, sometimes extremely so, but share almost the same set of genes. How do differences between the sexes arise from a shared set of genetic starting points and why do various species show wildly different degrees of sex differences? This research seeks to answer these fundamental questions using a remarkable group of insects, the bagworm moths. Both male and female bagworms start life as caterpillars that carry around a protective silk bag as they feed and grow. Males always mature into winged adult moths, but females can develop very differently depending on the species. In some species, females mature into winged moths whereas in others, females either never develop wings and remain much like a larva and crawl to find a mate, or do not develop legs or eyes and never leave their bag. By studying this diverse group of insects and their relationships, researchers will gain a better understanding of how sex differences are genetically controlled and why they vary across the tree of life. This project will provide training in systematics for two postdoctoral researchers and three graduate students. The researchers will collect bagworm species from around the globe to first construct a phylogeny of bagworms to determine how many independent transitions of sexual dimorphism have occurred. They will also test how larval bag structure, local climate, and other variables influence the evolution of sexual dimorphism. Researchers will generate genomic resources for key species exhibiting different levels of dimorphism to uncover the genetic mechanisms that control sexually dimorphic development in each case. This work will uncover the molecular underpinnings of novelty, discerning whether bagworms employ a common molecular framework or have evolved convergent strategies to achieve similar levels of dimorphism. Finally, researchers will assess the role of adaptation in the evolution of sexual dimorphism by testing for positive selection in genes expressed in males only or females only, especially on the sex chromosomes, which harbor many sex-biased genes. This work will help resolve outstanding questions of evolutionary genetics on the role that sex chromosomes play in adaptation across the genome. Results of this work will be disseminated to the broader community through a number of avenues including peer-reviewed publications, conference talks, a museum exhibit at the Florida Museum of Natural History, and a web comic distributed on social media. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.