Data from: Variation in genomic vulnerability to climate change across temperate populations of eelgrass (Zostera marina)

A global decline in seagrass populations has led to renewed calls for
their conservation as important providers of biogenic and foraging
habitat, shoreline stabilisation, and carbon storage. Eelgrass (Zostera
marina) occupies the largest geographic range among seagrass species
spanning a commensurately broad spectrum of environmental conditions. In
Canada, eelgrass is managed as a single phylogroup despite occurring
across three oceans and a range of ocean temperatures and salinity
gradients. Previous research has focused on applying relatively few
markers to reveal population structure of eelgrass, whereas a whole genome
approach is warranted to investigate cryptic structure among populations
inhabiting different ocean basins and localized environmental conditions.
We used a pooled whole-genome re-sequencing approach to characterise
population structure, gene flow, and environmental associations of 23
eelgrass populations ranging from the Northeast United States, to
Atlantic, subarctic, and Pacific Canada. We identified over 500,000 SNPs,
which when mapped to a chromosome-level genome assembly revealed six broad
clades of eelgrass across the study area, with pairwise FST ranging from 0
among neighbouring populations to 0.54 between Pacific and Atlantic
coasts. Genetic diversity was highest in the Pacific and lowest in the
subarctic, consistent with colonisation of the Arctic and Atlantic oceans
from the Pacific less than 300 kya. Using redundancy analyses and two
climate change projection scenarios, we found that subarctic populations
are predicted to be more vulnerable to climate change through genomic
offset predictions. Conservation planning in Canada should thus ensure
that representative populations from each identified clade are included
within a national network so that latent genetic diversity is protected,
and gene flow is maintained. Northern populations, in particular, may
require additional mitigation measures given their potential
susceptibility to a rapidly changing climate.