Social brains and behaviour in cooperative insect societies

The social brain hypothesis suggests that the cognitive demands of living in large, individually-based social groups selects for large brain size and enhanced cognitive abilities. This hypothesis has received some support from comparative studies of mammals and birds, but there have been very few experimental studies of the hypothesis. We will carry out experiments to test the causal relationship between sociality and brain evolution and development using a wild population of a paper wasps in southern Spain.

Primitively eusocial insects, which unlike eusocial insects do not exhibit morphological or task specialisation, exhibit wide variation in group size and social complexity. Group members form individually-based dominance hierarchies, exhibit individual recognition (e.g. based on facial patterns in Polistes paper wasps) and form long-term social memories of individual identity and strength. Within species, socially dominant females, and those that found nests in multi-female groups rather than alone, have been found to  possess larger mushroom bodies (MBs) than subordinate or solitary-founding females. Mushroom bodies are a region of the insect brain thought to be important in learning and memory.

Together these studies support the hypothesis that individuals living a socially rich or socially demanding life possess or develop brains that are morphologically distinct from conspecifics. However, previous studies have been correlational, and so the causal nature of this relationship is unknown. This project will address this shortfall in knowledge using a combination of innovative field experiments, bioimaging, and theoretical modelling.

Aims
The specific aims of the project are
1. To test experimentally the causal relationships between social status, group size and brain structure in a primitively eusocial insect, the paper wasp Polistes dominulus.
2. To test experimentally how social aggression influences brain development and cognitive performance.
3. To develop new theoretical models to explain variation in social aggression, social memory and emergent social structure in animal societies.

Methods
The project will use an established study population of paper wasps Polistes dominulus in southern Spain. Group members will be individually marked and videoed. Social status will be manipulated by temporary removal of dominant or subordinate individuals. Aggression will be manipulated using synthetic hormones. Imaging of dissected wasp brains will be carried out at the University of Exeter and micro CT images obtained in collaboration with the Natural History Museum. Training in mathematical modelling of behaviour will be provided.

Training opportunities:
The successful applicant will receive training in experimental design, measurement of behaviour, video analysis, and ecological data collection. S/he will be shown how to locate nests, mark individuals, design and execute experiments, video nests, and deal with inevitable unforeseen events that are inherent in field research. This is an excellent opportunity to develop the transferable skills to set up new projects in future.

The successful applicant will receive training in dissection, sample preparation and high resolution micro-CT scanning and imaging at the Natural History Museum, under the supervision of Dr Farah Ahmed.

Finally, the student will receive training in formal mathematical modelling of behaviour, including evolutionary game theory, dynamic games and stochastic dynamic programming. The problems to be modelled are well defined, and in the last few years a number of economic models have appeared which address problems that are strikingly similar (in the context of election timing and military/economic conflict). The successful student will be have an opportunity to adapt these economic models to a biological and evolutionary context for the first time.