THE GENETIC BASIS OF NATURAL VARIATION OF SOCIABILITY IN FRUIT FLIES

Abstract

Sociability is defined as the tendency of conspecifics to do non-aggressive activities with each other. In many species, being in a group increases fitness, making it highly relevant to understand. Fruit flies (Drosophila melanogaster) are an ideal model system to study sociability because of their complex social lives. A previous artificial selection experiment created evolved lineages of low and high sociability. Extraction, sequencing, and follow up genomic analyses of these lineages allowed us to identify candidate sociability genes. However, a causal link between genes and sociability has yet to be identified. The goal of this thesis was to functionally validate the effect of these genes. We used RNA Interference (RNAi) to knock down genes and measure subsequent changes in sociability between knockdown and control flies. Our predictions were based on the differential expression of each gene: We predicted that genes with lower expression in the low sociability lineages compared to the control lineage would have lower sociability scores than controls, and vice versa. We used circular 3D printed circular arenas like the ones in Scott et al., (2022) to measure sociability. We successfully verified 10 out of the 20 genes we tested. Sec5, CG13197, Ir94D, and Est-P altered sociability in the predicted direction. We also found that thoc5, CG8329, DJ-1, Net-A, FBgn0033353, and ppk28 also affected sociability, but in the opposite than predicted direction. Future work entails validating a second set of candidate genes that were identified based on population genomic work, investigating other social behaviours in some verified genes, and testing orthologs of verified genes in mice to understand sociability from an evolutionary perspective across various species.