The Genetic Basis of Family Effects and the Evolutionary Limits to Large Body-Size.

In organisms with parental care, a major determinant of an individual's success are the parental decisions that determine how much resource that individual should receive. Blue tit parents vary widely in how much resource they are able to provide to their offspring. Some of this variation will have a genetic basis, but currently we do not know whether genes play a major or minor role. By forcing blue tits to raise offspring that are not their own we can ask if the foster-offspring of two related mothers (e.g. sisters) grow at more similar rates compared to the foster-offspring of unrelated mothers. We can use the degree of similarity to say how much of the variation in growth rate is due to the action of genes expressed in parents. We also don't know whether individuals that have genes that make them provide more resources to their offspring are more successful. Providing more resources to their offspring helps their offspring to survive and transmit their genes into future generations, and so it has often been thought that these individuals have successful genes. However, a parent that provides fewer resources may have a better chance of surviving to the following year and reproducing again, and so maybe it is these individuals that have more successful genes? By looking to see which individuals survive from year to year, and counting how many offspring they have, we will be able to say which of these two strategies is favoured by natural selection, or indeed if the best strategy is a compromise between the two.

The amount of resources an individual receives from its parents is not fixed. Individuals can manipulate their parents into providing more food (via behaviours such as begging) but we do not know whether individuals have genes that control how manipulative they are. However, by placing relatives (e.g. brothers) in different nests we can see whether their two sets of foster parents provide food at similar rates. If they did, this would imply that there are genes shared by the two brothers that are manipulating their foster parents. Genes that make the brothers very manipulative would be good for the brothers (it would increase the amount of food they receive) and bad for the parents (they would have to work harder). However, it is unclear whether these genes would have detrimental effects on the brothers' nest mates. If a brother forces the parent to bring more food, is this food shared by all members of the nest, or does the brother commandeer all of the food, leaving less for its nest mates? If the former, manipulative genes would be beneficial for an individuals nest mates, but if the latter, manipulative genes would be detrimental to an individuals nest mates. We can distinguish between these two hypotheses by comparing the nest mates of manipulative brothers, and nest mates of non-manipulative brothers. If the nest mates of manipulative brothers are on average lighter than the nest mates of non-manipulative brothers we know that the genes for manipulation are bad for nest-mates.

The answers to these questions may help us to address a long-standing problem: large individuals tend to survive better and have more offspring than small individuals, and because size is heritable we would therefore expect most species to be evolving to be larger over time. This is not what we see. However, if the genes that make an individual large are also bad for parents (because they have had to work harder) or bad for siblings (because they are deprived of food) then perhaps large size will not evolve. This is because identical copies of the genes that make an individual large are also present in that individual's parents and siblings. A gene that makes an individual large directly benefits itself, but a gene that makes an individual small indirectly helps copies of its self in the individual's relatives. In this way genes for large size and small size may do equally well, and then we would not expect large size to evolve.

We anticipate that this project will have academic, industrial and societal impacts.

Academic Impact

i. Enhancing knowledge economy: Our work will provide new insights into the genetic basis and selective consequences of family interactions. Our results will be published in high impact journals and presented at national and international conferences. Our data will benefit future projects and will be made available via on-line repositories (Center for Open Science).

ii. Developing and training highly skilled researchers: The project will train ca. 10 people in the collection of standardised ecological data, three in molecular genetic methods and one in advanced statistical methodology.

iii. Developing and supporting new statistical methods: JDH has previously developed general purpose software tools (such as MCMCglmm) that are widely used across many academic disciplines. The work outlined in this proposal will add new features to MCMCglmm and it is envisaged that these will also be used widely, both by evolutionary biologists but also more widely across the data-driven sciences.

Societal impacts

i. Contributing to increasing public awareness and understanding of science: The number of UK citizens interested in natural history, and birds specifically, provides good reason to expect that the project and its findings will be of interest to the general public. We will establish a project blog and twitter account to interact with what we hope will be a highly engaged audience. We will encourage local public engagement through talks to local societies and an exhibit at the Edinburgh Science Festival. More generally, we will organise a wikithon for the large number of quantitative geneticists working in Edinburgh in order to improve the Wikipedia entries on quantitative genetics and its concepts. Wikipedia is one of the main routes by which the public can learn about scientific concepts, and providing non-techincal understandable information in this medium is central to improving public awareness and understanding of science.

Industrial impacts

i. Recently, animal and plant breeders have become interested in incorporating indirect genetic effects into their breeding strategies in order to increase food quality, production and animal welfare. JDH is a member of the Edinburgh Alliance for Complex Trait Genetics (e-ACTG), which includes members from outside of academia working on selective breeding in agriculturally important animals.The biannual e-ACTG meetings will give us a forum to reach a more diverse audience than is typical for specialized scientific meetings, and communicate our results to interested parties working in industry,

ii. As detailed under Academic Impact iii., this proposal will add functionality to MCMCglmm, a piece of software written and maintained by JDH and already used for industrial applications (JDH receives many emails a week asking for assistance, some of which are from employees in the private sector). The new functionality will have wide application in many statistical problems, and it is envisaged that this new functionality will be of benefit to all users, including those in the private sector.