Historical shell size reduction of the dogwhelk (Nucella lapillus) across the southern UK.

Body size reduction is predicted to be one of the most common ecological responses to climate change, yet examples within some taxonomic groups, such as marine molluscs, are rare. Here, we document a significant reduction in shell size of the rocky shore gastropod Nucella lapillus across the southern UK using natural history collections and modern field data. These results are correlated with temporal changes in sea-surface temperature from a long-term monitoring station. The maximum height of N. lapillus shells has declined by approximately 18 mm over the past 100 years, and the median size of shells in large size classes declined by 6 mm during this time. Individuals are, on average, larger in the west than in the east, which is noted using both modern and historical samples. In some locations, there has been a local extinction of N. lapillus, potentially due to combined negative impacts of climate warming and TBT pollution. Our results further demonstrate the utility of natural history collections, paired with modern field sampling, to document biological response to climate change and other human impacts.