The Role of the Foraging Gene (for) on Social Interaction Networks of Drosophila melanogaster

Social interactions are prevalent in the lives of many animals, including Drosophila melanogaster. D. melanogaster aggregate on fermenting fruit, creating complex social environments within which they display various social behaviours. Deciphering the genetic underpinnings of these social behaviours is a difficult task, and few studies have attempted to address this. Here, I investigate how the foraging gene (for) influences social networks in D. melanogaster. for is a well-established example of a pleiotropic gene that modifies behavioural phenotypes. In fruit flies, there are two naturally occurring alleles known as rover and sitter, that differ in their foraging behaviour. for regulates multiple phenotypes, the best known of these involves larval food-related behaviours. Recent studies suggest that for’s influence extends to social behaviours across a variety of taxa. In my thesis, I report that for plays a role in influencing both behavioural elements of social networks and social network measures. Rover flies are characterized by having greater interaction rates, moving more during the trial, and having higher global efficiency values. While sitter flies spend more time interacting, are more likely to reciprocate an interaction, and create more homogeneous networks in which they display higher clustering coefficient values. My initial findings establish that this natural polymorphism of for influences the behavioural elements and social network measures. Using gene dosage manipulations, I show that differences in behavioural and social network phenotypes are mainly due to differences in the for locus. To address this further, I attempt to investigate the critical period of for expression on behavioural elements and social network measures. I separately knockdown for in the adult stage, as well as from the embryonic until the larval wandering stage. I did not find an effect of these developmental manipulations on behavioural elements and social network measures. These results suggest that the critical period of for expression in relation to behavioural elements and social network phenotypes is likely within the pupal stage, during metamorphosis. I also use promoter-driven increased expression of for and show that the different for promoters may independently regulate different phenotypes within the analysis of social networks. I report that for's influence on social behaviour exhibits plasticity to the environment. I show that even though network measures are resilient to social isolation, food, and sleep deprivation, the behavioural elements of a network are responsive to these stressors. Finally, I examine networks of mixed groups of the rover and sitter flies to shed light on how these strains may interact when they are in the same group. In summary, this thesis characterizes the effects of a specific gene on social networks. My findings emphasize the complexity of for’s influence on Drosophila social behaviour and support the theory of genetic effects on social behaviour.

Keywords: behavioural genetics
Drosophila
foraging gene
social interaction networks
social network analysis
Advisor: Levine, Joel D.