On the use of kinship and familiarity associated social information in mediating Drosophila melanogaster oviposition decisions

Decisions about where to lay one’s eggs are of great importance, as the specific conditions in one’s offspring developmental environment may be critical to their subsequent survival and lifetime reproductive success. Information produced by conspecifics can potentially be useful to an individual’s oviposition decision-making process as this “social information” may provide an energetically cheaper means of assessing site suitability rather than acquiring it personally. However, not all conspecific public information may be equally beneficial, and cues produced by kin may be especially valuable as they might signal uniquely suitable microenvironments, as well as suggesting other fitness advantages resulting from improved foraging success and/or a decreased risk of competition/cannibalism amongst kin compared to sites where unrelated conspecifics are located. Using the fruit fly, Drosophila melanogaster , we explored whether public information use is associated with kin-based egg-laying decisions. Kinship is potentially recognized in several ways, including cues produced by environmentally-associated gut microbiota of the egg-laying flies, and so we also explored whether there were biases in how focal females interacted with cues from individuals that differed in both their genetic relatedness, as well as their environmental “familiarity.” In a series of inter-connected assays, we examined the egg-laying behaviour of females that interacted with a choice of potential egg-laying substrates that differed in the manner of their prior conspecific exposure. Not only do female flies lay more eggs on sites that had cues left behind by conspecifics compared to unexposed substrates, but they also exhibited strong biases in their oviposition patterns that was consistent with being sensitive to the kinship status of the prior substrate occupants. Furthermore, while females did not apparently discriminate between sites differing in prior egg abundance, they did exhibit bias in their egg-laying based on the population of origin of the demonstrator female. The basis of the kinship categorization by ovipositing females appears to be based on phenotypes that reflect true genetic relatedness that are neither mimicked nor disrupted by the conspecific’s developmental environment. These results highlight the potential usefulness of D. melanogaster as a model to understand the evolution of social behaviour in the expression of decision-making.