Climatic selection on body colour in Cepaea

Abstract

There is geographical variation in body colour in the land snails Cepaea nemoralis and C. hortensis along a transect of 88 samples from the north of Scotland to the Pyrenees. Paler body colour is associated with higher mean daily maximum temperature in both species. Laboratory experiments show that dark-bodied snails heat up more rapidly and reach a higher equilibrium temperature than do pale snails when exposed to radiant energy. Climatic selection favouring pale body colour in warm areas and dark body colour in cold areas is probably responsible for the association with climate.