The spatial scale of adaptive population differentiation in Atlantic Salmon
: local adaptation in smolt migration timing

Student thesis: Doctoral ThesisDoctor of Philosophy (awarded by UHI)


This research seeks to address the question of whether there is evidence for local adaptation in migratory behaviour of Atlantic salmon. Specifically, it aims to examine variation in the timing of smolt migration among independent tributaries of single river systems and to screen individual fish for molecular genetic variation at neutral microsatellite loci. Through integration of distinct yet complimentary disciplines, genetics and biotelemetry, this work is focussed toward identifying the spatial scale and extent of population genetic structuring in the species and linking this to variation in migratory behaviour.
From a purely academic perspective, investigation of local adaptation in run timing is important because it reflects a central component of the behavioural syndrome. By linking variation in an important life history trait to environmental features, one may better understand more general ecoevolutionary processes which shape present day genetic variation in freshwater systems and beyond.
Through assessment of fine scale genetic structuring and local adaptation, knowledge on how best to manage threatened populations may be gained. Through an investigation of how the environment can influence microevolutionary processes, constrain interbreeding and facilitate genetic divergence, this research is focussed on the identification of demographic populations and their relationship to the physical.
environment they inhabit. With such information in hand, management of Atlantic salmon may be defined not arbitrability, but at the scale of distinct evolutionarily units, which, according to current consensus, are best managed separately.
Ultimately, furthering knowledge of population structuring and fine scale variation in behaviour is important from a conservation perspective. By studying, the spatial structure of populations one may identify unique and adaptively important genetic variation. Maintence of this genetic diversity is important for the survival of individuals, and thus, the fitness and evolutionary resilience of populations, especially relevant for a species at crisis point, and in the face of global climate change.
In order to successfully undertake this research, a clear picture of the present extent and depth of knowledge on local adaptation in Atlantic salmon, and in general, is essential. To answer the explicit question, an understanding of the level of genetic differentiation among populations is necessary, as is data on the migratory behaviour of wild Atlantic salmon smolts. This will be obtained by the tracking of individuals as they move downstream using biotelemetry methods. To further link molecular genetic variation and differences in behaviour to more general features of the riverine landscape (i.e., tributary branching and habitat complexity), landscape genetic approaches will be employed with the specific goal of understanding how these features can influence evolutionary processes and ultimately variation in behavioural traits associated with migration.
Date of Award13 Dec 2023
Original languageEnglish
Awarding Institution
  • University of the Highlands and Islands
SupervisorEric Verspoor (Supervisor) & Benjamin Williamson (Supervisor)

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