Attractiveness of mates based on odours: the case of petrel seabirds – AMBO

Optimal mate choice relies on signals that broadcast compatibility and quality of potential mates. The interaction of such signals with the evolution of mate choice is largely acknowledged on the grounds of theory and empirical demonstrations involving mainly visual or acoustic based communication systems. Notwithstanding, a growing body of evidence indicates that odours are broadly used in individual, sexual and species recognition in vertebrates and may be reliable signals of quality and compatibility. However, the role of odour-based signalling in speciation has been little studied. A special case is represented by the Major Histocompatibility Complex (MHC) that was found to be involved in mate choice decision in several vertebrate taxa, including mammals and birds. The MHC contains the most polymorphic gene loci known in Vertebrates, and plays a central role in disease resistance and immune defence. By identifying and choosing a mate with dissimilar MHC genes a given individual can increase MHC polymorphism in offspring, and relative heterozygosity in MHC genes can increase offspring viability through enhanced immunocompetence and avoidance of costs of inbreeding. In several vertebrate species including mice, it was demonstrated that different MHC type may translate in odortype and be involved in mate choice. While, traditionally ornithologists had only rarely considered the role of chemosensory information in birds. Yet, every bird that has been examined has a functional olfactory system. However, compared to other organisms, information on the production or social use of self-produced odour compounds in birds has been largely neglected. Recent studies challenge this belief suggesting that odour may play an important role in birds mate choice. Research on mice has shown that genes of the MHC complex influence their urinary odours, and research on birds has shown that MHC may influence mate choice. This project address odour based individual and species recognition in petrels. Petrels among birds are the most suitable model to investigate chemical communication, they have probably the most sensitive sense of smell among birds and we demonstrated their use of olfaction to find their nest and recognise their mate. In addition, recently we showed the personal odour of an individual bird may be considered as an olfactory signature, and in behavioural experiment petrels avoided self-odour, when presented with the scent of another conspecific, showing thus a behavioural pattern reported in mice, and related to MHC genes: kin recognition and inbreeding avoidance through odortypes. The chemical nature and the genetic basis of petrels' olfactory signature are unknown however. The objectives of this research programme are as follows. 1) To explore the nature of signals allowing individual and species discrimination in petrels through chemical characterisation of odours. Bioassays with artificially reconstructed odour profiles will confirm the role of the identified compounds in different recognition processes. 2) To assign odour qualities to genetic characteristics and to clarify how they eventually lead to the choice of a particular mate. We will screen MHC complex in petrels and look for its involvement in mate choice and behavioural mate choice tests will link odour profiles and MHC characteristics. In addition, to overcome some experimental problems with petrels, we propose to assess objective odour qualities testing odour similarity using mice as a 'biological olfactometer' in a habituation–discrimination paradigm. 3) To highlight compounds indicating individual and species, comparing intra- and inter-specific odour signatures. 4) To assess the role of being nocturnal in odour based communication. Our project concerns chemical communication in birds: this topic is completely new and, to our knowledge, almost nothing is known except our precedent work. Our project is ambitious and interdisciplinary, crossing behavioural, chemical en genetic data in an evolutionary perspective. Our group already established international collaboration with the specialists of each step necessary to the project, that will allow to obtain rapidly good results, and at the same time to import in France skills and techniques both for screening MHC, and analysing the chemistry of vertebrate semiochemicals. Over all, if financed, our project will contribute to increase the position of France as a leader in challenging ecological research projects.