Evolution of limpet assemblages driven by environmental changes and harvesting in North Iberia

Two limpet species, Patella depressa and P. vulgata, are the most accessible molluscs in the upper intertidal shore on the coast of Asturias (Northern Spain) and have been consumed by humans for thousands of years, with evidence of harvesting-driven directional selection for size since the Palaeolithic. These 2 species are also highly sensitive to environmental conditions, P. depressa being in expansion under the current warming conditions. Our coalescent analyses of mitochondrial DNA suggest that both species are currently in a process of slow decline in population growth after experiencing a recent bottleneck, presumably enhanced by human exploitation. Over a wider temporal scale, the evolution of these species in Asturias seems associated with climate change, which seems to have driven their expansion across the studied zone. Current differential compositions of Patella assemblages associated with short-term differences in temperature on North Iberian coasts are consistent with the preferred conditions for each species. Human exploitation may have contributed to the most recent changes in limpet population diversity and morphology (size) at a short temporal scale, whilst climate would have caused long-term changes and would be responsible for most of their present population distribution.