Genomic vulnerability of a dominant seaweed points to future-proofing pathways for Australia’s underwater forests

Globally, critical habitats are in decline, threatening ecological,
economic and social values and prompting calls for “future proofing”
efforts that enhance resilience to climate change. Such efforts rely on
predicting how neutral and adaptive genomic patterns across a species’
distribution will change under future climate scenarios, but data is scant
for most species of conservation concern. Here, we use seascape genomics
to characterize genetic diversity, structure and gene-environmental
associations in a dominant forest-forming seaweed, Phyllospora comosa,
along its entire latitudinal (12o latitude), and thermal  (~14oC)
range. Phyllospora showed high connectivity throughout its central range,
with evidence of genetic structure and potential selection associated with
sea surface temperatures at its rear and leading edges. Rear and
leading-edge populations harboured only half the genetic diversity of
central populations. By modelling genetic turnover as a function of sea
surface temperature, we assessed the genomic vulnerability across
Phyllospora’s distributional range under climate change scenarios. Despite
low diversity, range-edge populations were predicted to harbour beneficial
adaptations to marginal conditions and overall adaptability of the species
may be compromised by their loss. Assisted gene flow from range edge
populations may be required to enhance adaptation and increase resilience
of central and leading-edge populations under warming oceans.
 Understanding genomic vulnerability can inform proactive
restoration and future-proofing strategies for underwater forests and
ensure their persistence in changing oceans.