A01

Genetic and epigenetic mechanisms of niche choice and niche conformance in a declining fur seal population

Joseph I. Hoffman & Toni Gossmann

Niche choice and niche conformance are key mechanisms that alter the match between an individual and its environment, resulting in individualised niches. However, while there is evidence for short-term fitness consequences of individualised niches, little is known about their long-term role. This is important because NC³-mechanisms may impact population dynamics and responses to environmental change. Two major mechanisms may underlie how individualised niches are established in the long-term: (i) gene-by-environment interactions, and (ii) epigenetic regulation, which have so far received little attention. To address both of these intriguing possibilities, we propose to investigate the long-term fitness consequences of niche choice and conformance, and how they interplay with genetic and epigenetic variation, using a rich and exceptionally detailed long-term study of Antarctic fur seals.

We will first investigate how niche choice and niche conformance optimise the interaction between an individuals’ phenotype and the environment by analysing four decades of highly detailed life-history data from hundreds of breeding females incorporating individual-based parameters such as age-specific fertility (i.e. pupping success) and breeding success (i.e. pup survival). Our study population of Antarctic fur seals at South Georgia has experienced strong environmental change impacts over the past four decades, as local warming and the loss of sea ice have progressively reduced the availability of Antarctic krill. Breeding female numbers have almost halved since the early 1980s, but they also fluctuate from year to year in response to shorter term changes in krill abundance.

Our long-term dataset will allow us to investigate how both contextual and ontogenetic plasticity shape individualised niches and fitness variation. We will evaluate whether breeding females choose specific temporal niches, for example by pupping only in the best years or by selecting years that offer the best fit to their own phenotypes, a process that might in turn be shaped by external predictive adaptive responses (PARs). We will also test the hypothesis that the probability of successfully raising a pup depends on a female’s short-term ability to conform to the prevailing environmental conditions as well as to the social environment ashore.

Detailed life-history data will then be combined with the latest cutting-edge ‘omics’ approaches to evaluate the mediating power of genetic and epigenetic effects on niche choice and conformance. Arguably, one of the most important genetic influences on fitness in wild populations is inbreeding, which we will quantify using a newly developed high-density SNP array. We predict that NC³-mechanisms will be constrained by inbreeding. By contrast, epigenetic mechanisms such as DNA methylation might mediate short-term responses to environmental variation as well as facilitate long-term responses to environmental change. We will therefore use a methylation-sensitive reduced representation sequencing approach (epi-GBS) to characterise genome-wide DNA methylation profiles, which in turn will be related to niche choice and conformance.

Overall, this project will provide a novel evolutionary (epi)genetic perspective on individualised niches while also generating detailed insights into how NC³-mechanisms feed into long-term fitness variation and ultimately population persistence.