PUBLIC GOODS AND SOCIALLY RESPONSIVE FEMALES

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Why and how animals cooperate with each other remains a fascinating challenge to explain. We know that individuals within families or that regularly interact with each other are far more likely to gain reciprocal benefits from cooperating with each other. However, there are many examples across the animal kingdom where these conditions don't hold and where cooperation is observed in situations in which it isn't predicted. We have recently uncovered such an example in our studies of the social responses of fruitflies. They don't live in familial or social groups, which predicts that they should be very unlikely to express socially cooperative behaviour. Nevertheless, we have found that females have remarkably fine-tuned responses to their social environments. For example, when they detect the presence of other females they very rapidly increase their rate of egg laying and alter their sexual receptivity. Eggs laid by groups of females that meet on food substrates females are laid together in clumps together with those of other females and, unexpectedly, these eggs seem to benefit from the cooperative protection offered by the eggs of other females.Laying eggs in communal batches seems to be beneficial because eggs are laid with an antimicrobial and anticannibalism 'coating': this diffuses and prevents spoilage of the substrate on which the eggs are laid, and prevents eggs from being eaten by any larvae that are present. The defensive coating protects batches of eggs (and resulting larvae) on a food patch. However, the production of these antimicrobial and anticannibalistic chemicals is energetically costly and potentially open to exploitation by others. This is because, if some individuals lay 'defenceless' eggs next to those with a strong antimicrobial coat or with effective anti-cannibalism defences, they can benefit without paying costs and hence can 'free-ride' the system. The explanation for what prevents most individuals from cheating like this resides in a powerful body of theory concerning 'public goods'. Key to the explanation is whether the benefits of producing public goods (i.e. the antimicrobial and anti-cannibalism defences) are 'non linear', for example if the only way everyone can benefit is if a threshold number of cooperating individuals pitch in. The aim of our project is to measure how and why cooperation over public goods occurs in our test system, and hence test the predictions of this important theory. Using the power of the fruitfly system, we can do this by experimentally manipulating the whole system, from the sensory inputs, to the production of public goods themselves, to the outcome in terms of the reproductive output of individual females.We will investigate:(1) The nature of benefits to females from responding to social environments through the production of public goods such as antimicrobial and anti-cannibalistic chemicals. (2) The shape of the relationship between the production of public goods and fitness.(3) The gene regulatory mechanisms underlying the production of socially responsive public goods.The results of this programme will provide a significant step forward in our understanding of fundamental components of social biology. These principles will have broad impact across taxa and will help to show us how and why we behave as we do.