Multi-population responses of elevated pCO2 in the common periwinkle Littorina littorea from the Northeast Atlantic.

Physiological responses to temperature are known to be a major determinant of species' distributions and can dictate the sensitivity of populations to global warming. In contrast, little is known about how other major global change drivers, such as ocean acidification (OA), will shape species' distributions in the future. Here, by integrating population genetics with experimental data for growth and mineralisation, physiology and metabolomics, we demonstrate that the sensitivity of populations of the gastropod Littorina littorea to future OA is shaped by regional adaptation. Individuals from populations towards the edges of the natural latitudinal range in the Northeast Atlantic exhibit greater shell dissolution and the inability to upregulate their metabolism when exposed to low pH, thus appearing most sensitive to low seawater pH. Our results suggest that future levels of OA could mediate temperature-driven shifts in species' distributions, thereby influencing future biogeography and the functioning of marine ecosystems. Please note that COI sequences generated and analysed during this study are available from GenBank www.ncbi.nlm.nih.gov/genbank (accession numbers: KP221321-KP221558).