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 temp...