| dc.description.abstract | The global population is expected to reach 9.7 billion people by 2050. Therefore, sustainable intensification of the food system to support the increasing population under a changing climate is vital. Aquaculture is the fastest expanding food sector globally, but projections suggest this industry will be severely impacted by anthropogenically induced climate change in the coming decades. Genomic selection has been highlighted by the Food and Agriculture Organisation (FAO) as an avenue to ensure the aquaculture industry will thrive under future climatic conditions, fast-tracking breeding of specialised lines. Following this line of reasoning, the work in this thesis aimed to contribute to the advances in genomic breeding of marine molluscs, a highly sustainable source of animal protein. In the first chapter, I reviewed the existing literature on shellfish aquaculture, exploring how the current production systems and aquaculture practices may impact the genetic diversity of the produced stock and, consequently, the success of any proposed genomic breeding in these taxa, alongside identifying the main gaps in our current knowledge in this field. Subsequently, each experimental chapter of this thesis then addressed a separate gap in our current understanding. In chapter II, I developed a multi-species 60 K SNP-array applicable for genotyping four mussel species relevant for aquaculture: M. edulis, M. galloprovincialis, M. chilensis and M. trossulus. Following low-coverage whole genome sequencing of 138 mussels, ~60K SNPs were implemented in the platform, from which 23,252 are applicable for genotyping M. edulis individuals, 22,165 for M. chilensis, 20,504 SNPs M. galloprovincialis and 20,149 for M. trossulus. This tool therefore represents a major advance in the current technological capability available in this species complex, and will allow researchers to explore the genetic diversity of mussels using a dense number of markers (on the scale of thousands), whilst producing comparable data among studies. It is also applicable for breeding purposes and may facilitate future implementation of genomic selection in these taxa. Subsequently, in chapter III, I applied this SNP-array to explore the genomic structure of blue mussels in South West England; an important area for mussel aquaculture and a region that has been key for our understanding of hybrid zone dynamics, between the species M. galloprovincialis and M. edulis, historically. Results from this chapter agree with the previous description of the hybrid zone, with M. galloprovincialis genotypes
dominating the north coast of Cornwall whilst M. edulis is the prevailing species in the southern coast
of SW England. Furthermore, the transition zone between the two species was located at Lizard Point.
These results validate the utility of the SNP-array for determining speciation across a wide region, and
update our knowledge in genotype distribution in this key hybrid zone. In the thesis’ fourth chapter, I
explored how selection towards environmental resilience impacts the phenotypes and/or genotypes
of blue mussels. For this, I compared the genetic diversity and performance of juvenile mussels
exposed to a thermal stress event to those of individuals which did not faced it. Results from this
chapter suggest that thermal resilience may impact the performance of mussels, as stressed individuals presented a lower dry tissue weight (g) than naïve ones. In addition, a shift towards M. edulis genotypes occurred in the selected cohort. With climate change expected to increase the average sea surface temperature of the ocean, results presented in this thesis shows that such changes may impact the genetic background of mussel spat in the Baltic Sea and possibly. Such results may also impact aquaculture production of this species. In the final chapter, I discuss how the research questions explored in this thesis advance our knowledge in marine bivalve genomics and how they may change the field by supporting the development and application of genomic approaches for breeding these taxa. | en_GB |
