SG: Evolutionary history and contemporary function of alternative supergene haplotypes

University Of California-Riverside, Riverside CA

Investigators

Abstract

Even before the structure of DNA was described, biologist Theodosius Dobzhansky predicted that complex traits of organisms should be controlled by groups of closely related genes. He called these 'coadapted gene complexes' and hypothesized they should be passed on to offspring as a unit. These units would keep certain beneficial combinations of genetic variation intact in the next generation. Today, genome sequencing technology allows research into whether coadapted gene complexes, also called 'supergenes', indeed control complex traits. One such trait that has inspired curiosity in humans is social organization. How are cooperative behaviors encoded in the DNA of social organisms? Previous research found a large supergene associated with variation in a complex social trait in ants. This supergene contains units of more than 600 genes that are passed together as a unit to offspring. By contrast, most of the genome is shuffled from one generation to the next to ensure that offspring inherit different genetic variation from each parent. In multiple Formica ant species, individuals from colonies that consist of a single queen and her offspring have one variant of this supergene. Individuals from colonies that contain multiple queens have a different variant. The goal of this project is to learn how these supergenes appear and persist in groups of species, how they work, and how genes shape social behavior. This project will be an important step in understanding how and why supergenes form, and also in developing the link between genes and social behaviors. This project will also provide opportunities for undergraduate research training and introduce K-12 students to the study of social insects. The PI and co-PI have recently identified two ant species that each carry three alternative variants of the supergene. This project will take advantage of one population of each species where three haplotypes co-occur. Using these populations, the researchers will characterize the variation among alternative haplotypes at the supergene and link that variation to functional differences. In particular, differences in phenotype and fitness will be investigated with a series of mating and brood rearing experiments. The experiments will include queens with each possible genotype in each species. Additionally, the gene order, recombination rates, and zones of suppressed recombination between alternative haplotypes will be assessed through high density linkage mapping and whole genome sequencing, in order to reconstruct their evolutionary history. 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.