Variation in ageing rates in the wild

Wild animals frequently show declines in reproductive performance and survival probability in later life. However, individuals can show enormous variation in the age at onset and rate of these senescent declines. Because these changes in demographic rates impact individual fitness, they have important consequences for ecological and evolutionary processes. Understanding the drivers of among-individual variation in ageing trajectories has therefore become an important question in evolutionary ecology. Research on humans and laboratory model systems demonstrates that genes and environmental conditions can influence when and how quickly an individual ages. In addition, evolutionary theory predicts that investment in costly activities such as growth and reproduction will have negative consequences in later life, exacerbating the ageing process. However, we do not yet have a clear picture of the relative importance of genes, environment, and early life-history in generating variation in the rate of ageing across individuals in natural populations.
This project will utilise an exceptional long-term field study of wild Soay sheep on the remote St Kilda archipelago, off the west coast of Scotland. Detailed data are available for thousands of sheep, including information on individual fitness components, life-history traits, ranging behaviour, and morphological, physiological, immunological, and parasitological measurements. Individuals in this population have been extensively genotyped, and experience considerable variation in environmental conditions. This represents an excellent opportunity to understand the relative importance of genetic vs environmental effects in determining among-individual variation in senescence in a range of traits. The detailed morphological and life-history data collected over the life-course will also enable us to relate early-life investment in growth and reproduction to later ageing rates.