Source and maintenance of recognition cues in ant societies

Distinguishing group members from non-group members underlies a vast array of key animal behaviours, such as territoriality, altruism and mating. This requires variation in recognition signals but it is not known how this variation is maintained. Invertebrates, and many vertebrates, primarily use chemicals to encode information about an individual's species, sex, age or caste, in addition to alarm and trail pheromones. Ants are among the most dominant animals in the world and employ particularly rich forms of chemical communication since they are social, living in colonies containing tens to millions of individuals. Ants comprise five of the world's top seventeen most costly pest insects. Despite their importance as both beneficial and pest species, there is little knowledge about the recognition signals they employ. In fact, it was over 100 yrs ago that it was first suggested that ant recognition was based on chemical cues present in the waterproof layer that coats the outer surface of all insects. Very recently this has been confirmed by demonstrating that chemicals known as cuticular hydrocarbons found on the surface of Formica ants are indeed used in nest mate recognition. We will exploit this recent knowledge to study the genetic and environmental forces that underpin the maintenance of variation in ant recognition signals. To achieve this, we will conduct behavioural, biochemical, genetic and theoretical studies on the ant Formica exsecta and several of its close relatives. Formica ants are a keystone ant genus, comprising over 160 species, including the well-known mound-building wood ants and thus are one of the best studied groups of insects. Therefore, there is already a vast wealth of chemical, genetic, spatial and behavioural data, especially for F. exsecta, which has being studied over the past 15 years by Helsinki University with whom we are collaborating. To achieve our main aim we will conduct three parallel studies: 1) A biochemical investigation to track the production, transportation and eventual secretion of the key cuticular hydrocarbons (CHC) in F. exsecta. This will allow us to understand how and where an individual odour develops. 2) A study aimed at dissecting the genetic and environmental components of variability of the CHC (odour) used by F. exsecta and other Formica species. This will be achieved using the latest molecular tools. For the first time, we will construct a family tree within a single population for over 100 colonies to work out the heritability of the chemical cues. We will then produce a genetic map which will allow the genes that are involved in the production of the key hydrocarbons to be localised. We will test the role of candidate genes, using the genomes of the honeybee and Drosophila, and test for evidence of balancing selection on these genes. 3) Finally, using agent-based modelling we will investigate theoretically the evolution and maintenance of recognition cue variation (at individual, colony, species levels), within a spatial environment that can be subject to different conditions. We will use our empirical data to avoid previous problems associated with over-simplification of the system. In addition to being at the forefront of the rapidly emerging field of chemical ecology, this study helps in two key areas of UK insect conservation. Firstly, in the UK, F. exsecta is a Category 1 threatened species, so we will provide vital information and expertise to underpin the species' conservation. Secondly, understanding how environmental forces interact with genetic variation will provide new insights into the evolution and maintaince of recognition systems not only in ants but in many species of insects since the chemicals we are investigating are synthesised by almost all invertebrates.