Genomic basis of sexually divergent traits in red deer (Cervus elaphus)
Sexually selected traits show large variation and rapid evolution across the aniaml kingdom. The genetic variation underlying sexually selected traits is often maintained despite apparent directional selection, with proposed explanations including sexually antagonistic selection or trade-offs with other life-history traits, such as survival. A key step in uncovering evolutionary drivers and constraints of these traits is to understand them at the genomci level. However, few empirical studies have attempted to investigate this aspect in the wild. Using long-term data from a population of red deer on the Isle of Rum, Scotland, this thesis both investigates the genomic basis of antler morphology, an important sexually selected trait, and genome-wide signals of sexually antagonistic selection through viability selection across the genome. Antlers are a form of sexual weaponry in male red deer and are assocaited with increased breeding success. I show that antler morphology is highly repeatable over an individual's lifetime, heritable and that almost all examined antler morphology traits are positively genetically correleated. The investigation of causative loci underlying antler morphology showed that it has a highly polygenic architecure, with some loci identified as having potential pleiotropic effects. The finding suggest that a large mutational target and genetic covariances among antler traits, in part maintained by pleiotropy, are lifely to contribute to the maintenance of genetic variation in antler morphology in this population. In species with two sexes, males and females largely share the same genome. However, due to differing biology and life histories, the sexes can have divergent itness optima for the same traits, thus resulting in sexually antagonistic selection, i.e., sexual conflict. Evidence for sex-specific transmission distortion was found in the deer, which pointed towards sexually divergent selection on parental gametes and prenatal viability. No genetic loci underlying differntial mortality between males and females at later life stages could be identified. Among the loci under sex-specific selection, several showed evidence of balancing selection could be linked to candidate genes. These results support onging sex-specific, but not sexually antagonistic. selection on parental haplotypes and offspring genotype during prenatal development, with potential trans-generational effects. These selection patterns likely contribute to the maintenance of genetic variance and thus eveolutionary potential in this population of red deer.