The role of additive and non-additive genetic effects during animal contests in the beadlet sea anemone Actinia equina

Variation between individual animals in their behaviour should be influenced by their genes and by their environment. Moreover, an animal's environment should interact with its genes modifying how they are expressed outwardly in the individual's phenotype. Understanding the relative contribution of these two sources of variation is key to understanding the evolution of critical behaviours. One of the most important areas of behavioural variation among individuals is in their fighting ability, because this determines their access to critical resources. In many examples of fighting animals we see variation in aggression and from an evolutionary point of view this is a puzzle. If evolution produces selfish individuals, and high aggression lets them win resources, why do we also see meeker individuals that cannot win against aggressive opponents? A set of theoretical arguments have been made that provide explanations for why we see this range of aggressive behaviour in animal populations. But without data on interactions between genes and environments we can't gauge how well these theories match the real world. Crucially, in fighting and other situations where there is a conflict of interest, an individual's rival (and therefore it's genes) form part of that individual's environment. To fully understand the evolution of aggressive behaviour we therefore have to understand not only the direct genetic contribution to an individual's aggressive behaviour; we also have to understand how this is modified by the behaviour and ultimately the genes of its rival. This effect is known as the 'genotype-by-genotype' interaction effect and at present very little is known about this for any animal, or for any type of conflict behaviour. He we will study genotype-by-genotype interactions in sea anemones. These are very common on the coasts of the UK and they are an excellent species to work on because they reproduce asexually, meaning that we can repeatedly look at fights between different clone-lines. Their fighting behaviour, as well as the outward characters that contribute to fighting ability are well understood. In this project, we will look at genotype-by-genotype interactions, variation in aggression within and between genotypes, the effects of past experiences of fighting and the effects of the degree of relatedness of fighting rivals. In this way we aim to solve long-standing questions about the evolution of aggressive behaviour. By the end of the study we hope to be able to explain why some individuals are more aggressive than others in animals.

Aggression is very common in humans and non-humans. A full understanding of why aggression occurs, and persists, so widely across animal taxa requires that we also consider its evolution. A longstanding question is why variation in aggressive behaviour and fighting ability (RHP) is maintained in animal populations. Game theory proposes that negative frequency dependent selection can maintain a stable mix of strategies, but it does not account for the potentially complex genetic architecture that underlies variation in aggression. In particular indirect as well as direct genetic effects are likely to influence an individual's aggressive behaviour. Therefore we will study the role of additive and non-additive genetic effects (i.e. genotype-by-genotype interactions, GxG) for the first time in the context of animal contests. We have chosen the beadlet sea anemone Actina equina as out study system. These animals fight readily and reproduce asexually, allowing for the repeated contests between genotype pairs necessary for robust statistical analysis using mixed-effects models. GxG interactions will be studied from the perspective of both current and previous opponents, both of which are contribute to an individual's social environment. Recent studies show that consistent among individual and among genotype variation are partly dependent on within-individual consistency, and we will also assess the effects of genotype on this spontaneous intra-individual variation in aggression. Finally, we will use AFLP analysis to directly measure relatedness between genotype pairs, enabling us to assess how GxG interactions are modified by genetic similarity. The overall aim of this project is to resolve a longstanding question in animal behaviour; how is variation in aggression maintained in animal populations? We will use approaches from research on animal contests, animal personality, quantitative genetics and population genetics to answer this question.

The wider impact of this research is likely to be in the areas of (1) enhancing the research capacity, knowledge and skills of businesses and organisations and (2) increasing public awareness and understanding of science.

Animal science is strongly aligned with research into methods of refining livestock production and the welfare of farmed animals (including aquaculture). Despite current advances in cloning vertebrates and potential future use of cloning as a means of enhancing livestock production, no research has yet been conducted on the potential for inter-individual aggression levels to be influenced by genotype by genotype interactions. Knowledge of genotype by genotype interaction effects could be used to enhance welfare and production by selecting individuals with compatible genotypes (i.e. combinations that will produce low aggression) for housing. Basic knowledge of whether this is likely to be a potential issue will be provided by our studies on a highly tractable model system. If genotype by genotype interactions influence aggression levels in sea anemones this would point to the need for future studies of additive and non-additive genetic contributions to aggression in other animals including livestock animals as well as ornamental animals used in the aquarium trade.

There is a huge public thirst for new information about the natural world, and in this project we will make new discoveries about a species that anyone living in the UK can readily encounter in its natural setting, and where related species are easily accessible globally. Furthermore, the core ideas underlying the research, the links between genes and behaviour, are of fundamental interest to the public and the concepts of animal personality and aggression are proven to attract the attention of the media. Therefore, this project is provides excellent opportunities for public engagement with science, in particular demonstrating the importance of fundamental science that can nevertheless be applied to tackling wider issues.