Spread of social information and dynamics of social transmission within Drosophila groups.

Understanding how behavioral diversity arises and is maintained is central to evolutionary biology. Genetically based inheritance has been a predominant research focus of the last century; however, nongenetic inheritance, such as social transmission, has become a topic of increasing interest [1]. How social information impacts behavior depends on the balance between information gathered directly through personal experience versus that gleaned through social interactions and on the diffusion of this information within groups [2, 3]. We investigate how female Drosophila melanogaster use social information under seminatural conditions and whether this information can spread and be maintained within a group, a prerequisite for establishing behavioral transmission [4]. We show that oviposition site choice is heavily influenced by previous social interactions. Naive observer flies develop a preference for the same egg-laying medium as experienced demonstrator flies conditioned to avoid one of two equally rewarding media. Surprisingly, oviposition site preference was socially transmitted from demonstrators to observers even when they interacted in a cage with only unflavored, pure agar medium, and even when the observer flies had previous personal experience with both rewarding media. Our findings shed light on the diffusion process of social information within groups, on its maintenance, and ultimately, on the roots of behavioral local adaptation.