Morphological Variation and Genetic Differentiation in Wild and Domestic Atlantic Salmon from Southern Newfoundland

Abstract

Adaptive divergence is an important force structuring wild populations and directly influencing species persistence and stability. Wild Atlantic Salmon (Salmo salar) have declined across their native range in recent decades with genetic interactions with salmon aquaculture identified as a contributing cause. Improved understanding the nature of diversity in wild populations and the potential impact of interbreeding with domestic escapees is critical to conservation and management of wild Atlantic Salmon. Body shape of juvenile Atlantic Salmon in the wild may be considered adaptive and is often found to be associated with environmental and watershed conditions, or even with culture conditions in the case of domestic conspecifics. In this thesis I quantify the importance of body shape on population structuring in the wild, and then explore the impact of wilddomestic hybridization on shape of juvenile Atlantic Salmon. Geometric morphometrics were used to quantify and allow for statistical testing of variation in body shape. Geometric morphometric data were first combined with a large panel of sequenced microsatellite loci to understand the relationship between shape and population structure; and second used in conjunction with a SNP panel designed for wild-domestic hybrid identification to explore shape differences among cross types. My results suggest that variation in body shape is important to the structuring of wild populations, but that variation in climate was also significant in genetic structuring. Interestingly, shape differences between wild, domestic, and hybrids were minimal, likely reflecting both selection and phenotypic plasticity in the wild. My results suggest that phenotypic variation in body shape may be an important component of adaptive diversity among Atlantic Salmon populations, and that changes in body shape in the wild due to interbreeding with escaped farmed salmon may be minimal and masked by plasticity.