The evolutionary genomics of life-history adaptations and disease susceptibility in pinnipeds

Pinnipeds (seals, sea lions, fur seals and walrus) are keystone marine predators, and sentinels for marine ecosystem health. Advances in genomics technologies are opening up the possibility to identify and dissect the genetics and molecular evolution underlying the adaptions of pinnipeds to the marine environment and the startling variation in ecology and life history present within the family. Understanding these mechanisms not only provides fundamental insights into the process of evolution, but is also important for assessing species vulnerability and responses to potential future environmental change. Some of the unique adaptions of pinnipeds may also be of relevance to human health and therapeutics, such as adaptations in fat metabolism.

This project will build on rapidly growing genomic resources for pinnipeds, including de novo seal genome assemblies generated by the Goodman/O'Connell lab and other colleagues in the Pinniped Genome Consortium. These provide an opportunity to use comparative genomics to examine key aspects of pinniped ecology and evolution including physiological adaptations underpinning different life-history strategies and among species variation in disease susceptibility. We will use a variety of genomic approaches including de novo sequencing of seal genomes, and population genetic studies at the genomic level using methods such as ddRAD.

Among the 33 extant species of pinnipeds there are a diverse array of adaptations to varying ecological conditions and life histories. One of the most striking aspects of pinnipeds is the variation exhibited in foraging and reproductive strategies, which are associated with among species body size variation, and the habitats they exploit.

The harbour seal (Phoca vitulina) is the world's most widely distributed pinniped species, and in Europe has a range extending from Svarlbard to Northern France, and from the Baltic to the west coast of Ireland. Within this distribution the species exploits a wide variety of habitats and experiences a large range of environmental conditions. The species has also experienced 2 mass mortalities from phocine distemper virus (PDV; a member of the morbillivirus family), which killed more than 50% of the European population in 1988 and 2002. Levels of mortality varied substantially among populations, and intriguingly, grey seals (Halichoreus grypus), which are sympatric with harbour seals in much of Europe, were exposed to PDV during the epizootics but did not suffer extensive mortality. The species is therefore is a good model for examining how environmental and ecological conditions influence population structure in marine mammals and for evaluating how genetic variation might contribute to within and among species susceptibility to morbilliviruses.

In addition to whole genome comparisons we will also use ddRAD, and MiSeq sequencing of immune related candidate genes to examine population structure, demographic history, and associations between PDV mortality and genetic variation.

Expected outcomes: New knowledge on the molecular adaptions underpinning variation in pinniped life-history strategies; a detailed understanding of the way environmental factors influence population structure in a long-lived, marine mammal; insights into the population demographic history of harbour seals over long and short timescales in relation to past environmental change; potential identification of adaptations and functional genetic variation in harbour seals from across their geographic range and their genomic basis; identification of genetic variation contributing to within and among species variability in susceptibility to PDV; generation of data relevant to the conservation management of seal populations.