Data from "Cross-depth connectivity supports the role of deep kelp forests as refuge from climate change"

Abstract: Ocean warming and marine heatwaves are threatening the persistence of kelp forests butcooler, deeper reefs might act as refuges from which shallow population can recover. Despite this, little is known about the connectivity, genetic diversity and adaptive structure of deep kelp reefs.
We used genomics (ddRAD sequencing) to compare neutral and adaptive genetic diversity and determine the genetic connectivity between deep (30-50m) and shallow (10-15m) kelp forests of the kelp Ecklonia radiata within three regions in Western Australia (Abrolhos, Albany and Esperance). We also compared allele frequencies of loci putatively under selection across depths and between the warm range edge and cooler populations to better understand adaptation across contrasting environmental conditions.
There was no difference in genetic diversity and weak neutral genetic differentiation between depths at each location, supported by high bi-directional gene flow. The SNP outliers revealed broad-scale adaptive divergence across the sampled range marked by numerous fixed alleles under selection. Depth-specific selection was only identified at the warm edge population (Abrolhos Islands), with elevated levels of loci under selection and adaptive genetic differentiation between depths. These SNP outliers were linked to genes involved in to thermotolerance, light sensing, immune response and general environmental stress responses.
At high latitude, the extensive gene flow across depths and the lack of adaptive differentiation suggest high potential for deep kelps to assist in the recovery of shallow populations following climate-mediated loss. In the warmer range edge populations, differential selection between depths, likely due to greater adaptation to local environmental conditions, could lead to maladaptation if shallow reefs are reseeded from deep reefs following loss. Hence, the role of deep reefs as refugia from which shallow reefs can recover following climate-mediated loss is spatially dependent on local selective regimes.