Species in Polar Regions are very sensitive and have evolved specializations over time to successfully survive and reproduce in their unique habitats. Ongoing global climate change is disproportionately affecting polar species, and the question of whether they can cope and adapt to such changes is urgently pressing.
Seals are often considered icons for how organisms evolve to adapt to their environment, and they have developed different strategies to successfully produce and raise offspring. The females of some species, called capital breeders, build up large fat reserves, allowing them to give birth and nurse their pups for periods of up to several weeks without feeding. These females may transfer as much as 30% of their body mass to their pups, and seal milk contains the highest levels of fat of any mammal species. The females of other species, called income breeders, don’t build large fat reserves, and instead regularly leave their pup to forage. Within the family Phocidae, Southern elephant seals (Mirounga leonina) are champion capital breeders, while Weddell seals (Leptonychotes weddelli) use mixed strategies, and the harbour seal (Phoca vilutina) relies more strongly on foraging while nursing their pups. It remains unclear how the physiology of seals has evolved to enable these different strategies.
This project will use genome-scale data to address the following questions:
1) What is the evolutionary history of phocid seals and what are the phylogenetic relationships between capital and income breeding species? How has past climate change influenced their evolution?
2) Have strictly capital breeding species evolved specially adapted cellular pathways to convert energy to fat, store it, and then mobilize it to produce milk with extremely high fat content?
3) Does differential gene expression play a role in facilitating the use of mixed strategies?
Because income breeding is relatively much more common, it has been hypothesized that capital breeding may have evolved to deal with limited or unpredictable food availability. With the global climate changing rapidly, and industrial fishing impacting marine food webs, food resources for seals around the world are likely changing in both their predictability and abundance. An understanding of the physiological basis for building and utilizing fat reserves to nourish their pups could provide important insights for understanding the ability of seals to adapt to environmental changes and for managing healthy seal populations in the future.
Methods. The student will implement next-generation DNA sequencing to obtain genome-scale sequences of seals. They will conduct sophisticated bioinformatics processing, and then use advanced phylogenomic methods to build a time-calibrated species-level phylogeny to address questions about the timing and drivers of evolution and environmental adaption in this group. The student will then identify substitutions in the DNA sequences of these species, perform enrichment tests to identify the functions of genes impacted by these changes, and conduct tests of positive selection to investigate if the substitutions occur significantly more than expected by chance in candidate genes related to fat synthesis, breakdown, storage, and milk production. Finally he or she will conduct a gene expression study on one focal species exhibiting mixed strategies to identify differences in gene expression levels.
Training: The student will be based in the Biosciences Department at Durham University. The department has a strong track record in the fields of ecology and evolution, and a friendly and collegial environment. Our larger Molecular Ecology special interest group is composed of four PIs and involves a large group of postdocs, PhD and MS students that provide a supportive network for journal clubs, student presentations, peer feedback, mentoring for job applications and interview skills. The student will develop a number of key skills through completion of the project. Overall, the project will give a strong foundation in genomics, molecular systematics and evolutionary biology for a future academic career. Many skills developed are also widely sought for other careers: cutting-edge genome-sequencing can be applied for jobs in industry and environmental/health testing; computer programming and statistical analyses are well suited to the burgeoning number of jobs in bioinformatics and IT; and skills developed in teamwork, problem solving, writing, and effective communication are beneficial for any career.
For more info see: https://sites.google.com/site/andreannajwelch/jointhelab/phd-studentship-opportunities
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