Epigenetic stability and plasticity of social environmental effects

Sarah Benhaiem

Social status significantly affects Darwinian fitness by altering health, life history, and physiological trade-offs. Because social status is usually stable throughout life and is a behaviourally transmitted trait, social inequalities persist within and across generations. Even so, the molecular mechanisms underlying these social effects are poorly understood. We hypothesize that DNA-methylation is a main epigenetic pathway through which an individual’s social environment regulates gene expression and hence physiological responses and life-history trade-offs. We predict that methylation patterns in individuals experiencing social stability will promote status-specific trade-offs. We further predict that when the social environment results in status changes  as when high (low) born offspring are reared by a low (high) status surrogate mother, plasticity in methylation patterns should match the gene regulatory pathways, life-history trade-offs and fitness to the new social conditions. We test our hypothesis using long-term data obtained from spotted hyenas in the Serengeti National Park. To assess the impact of status-specific methylation patterns on health, we will measure faecal immunoglobulin, cytokine levels and eukaryome diversity, and will control for the possible confounding effect of gut microbiomes. By linking for the first time in a wild social mammal changes in social status to DNA-methylation, fitness and health, this project will shed light on gene pathways underpinning social inequalities, their plasticity, health consequences and potential implications for humans.