Local adaptation to pH variability in purple sea urchins

There’s little known about the mechanisms underlying adaptation to variable environmental conditions, especially in populations experiencing high gene flow. Phenotypic plasticity, which involves the differential expression of genes in response to external stimuli, often evolves in such environments, and thus, the evolution of gene regulation is hypothesized to play a major role in the adaptation to environmental variability. Different populations of purple sea urchins have been experiencing different magnitudes of pH variability for millions of years and as a consequence has evolved phenotypic plasticity but with population-specific differences. In this study, the whole genome of 140 purple urchins from 7 populations experiencing different pH variabilities was sequenced and a set of mutations putatively involved in local adaptation were identified, despite the urchin’s mobile larval life stage causing high gene flow. We found a significantly higher proportion of these mutations to be located in regulatory regions and transcription factors, supporting the idea that the evolution of gene regulation is important in adaptation to variable environmental conditions