Genomic signs of local adaptation to low pH across a natural CO2 gradient in the sea urchin Arbacia lixula

Our study aims to explore genomic signs of adaptation to OA in A. lixula populations living across a natural pH gradient at the coast of Fuencaliente (Canary Islands, Spain). To address this, 74 samples from four sites influenced by different levels of pHs (vent1 = 7.4, vent2 = 7.6 transition1= 7.8, transition2= 7.9, control = 8.1). A total of 14,883 SNPs were identified using 2b-RADSeq and 432 loci were correlated with the pH gradient according to redundancy analysis (RDA) and consequently, were considered potential SNPs candidates under selection. From these candidate SNPs and despite the short geographical distances among studied populations, a pattern of significant changes in genomic structure was found to be correlated with the pH gradient.