SFB-TRR 212

Social niche-mediated reproductive phenotypes

Over their lifetime, animals are exposed to a multitude of different conditions in their environment, whereby interactions with conspecifics as part of the social niche have a major impact on fitness. With this research project I want to understand to what extent individuals integrate the information gained from their surroundings into their phenotype. Further I want to test how conformance to the environmental and social conditions affects fitness. I will address how cues received in the larval environment affect adult morphology and behaviour, with a focus on reproductive traits. Using the fruitfly Drosophila melanogaster, I will manipulate a trait known to alter adult reproductive morphology in both sexes, namely population density experienced by larvae. This can inform individuals about the reproductive competition to be anticipated as adults. The observed morphological changes are expected to allow animals to conform to a high versus low competitive environment and to gain high reproductive success in the respective social environment.

However, if the environment fluctuates, individuals might find themselves in a mismatch situation and should suffer from reduced fitness. I will directly test these ideas by manipulating larval density and assess adult reproductive success under adult density conditions matching or mismatching the larval density experience. Apart from morphology, I also expect behaviour to be shaped by early experiences. I will assay adult behaviours for individuals who previously experienced a low versus high larval density environment, and I will further manipulate their current social group size and composition. In these setups, I will then measure aggression and mating behaviour, and test whether the current social environment alters expression of these behaviours. I can thus examine whether and how cues from conspecifics in the early versus the current environment interact in shaping individual behaviour.

These interacting individuals are part of each other's social niche and form the selection pressures acting on these individuals. As both early versus current social interactions are expected to shape evolutionary trajectories through indirect genetic effects, I will combine a modelling and an experimental evolution approach to measure genetic and phenotypic responses to low versus high density environments to understand how niche conformance might alter the rate of evolutionary change. Hence this comprehensive project will be an important step towards understanding how animals affect their own rate of evolution by predicting and conforming to their individual niches.