Abstract
Wildlife management and conservation requires knowledge about a species’
population structure, diversity, demographic history and adaptive
potential. However, often such information is lacking, or based on
insufficient and sometimes contrasting data. This is the case for the
grey seal (Halichoerus grypus), for which there remain uncertainties
regarding subspecies and population delineations, diversity and recent
evolutionary history, despite numerous genetic and non-genetic studies.
Here, we present the first range- and genome-wide population genomic
analysis of grey seals based on 3,812 nuclear SNP markers genotyped in
188 samples from 17 distinct localities. Our analyses support the
existence of three main grey seal populations centred in the NW
Atlantic, NE Atlantic and Baltic Sea, but also point to the existence of
previously unrecognised substructure within the NE Atlantic, in
particular separating grey seals sampled in Iceland, Norway and Russia
from the core NE Atlantic population inhabiting the wider North Sea
region. We detected remarkably low levels of genetic diversity in NW
Atlantic grey seals, which may be the result of evolutionary founder
effects, as well as more recent historic hunting and culling. We also
found some localities that deviate from the general isolation by
distance pattern, likely reflecting wide-scale metapopulation dynamics
associated with recolonisation and recovery of grey seals in regions
where they were historically extirpated. Our genetic results allow us to
identify at least six grey seal management units across the species’
Atlantic range, but also highlights knowledge gaps that should be
addressed in future research into this species.