Polymorphism in relation to habitat in the snail Cepaea hortensis in Iceland.

Polymorphism for shell colour and banding pattern in Cepaea hortensis was studied in a confined area in south Iceland. Morph freqquencies can be related to habitat. Yellow unbanded snails are more frequent in grassland and herb meadows thatn in "darker" habitats such as in ddense Angelica . Fused banding is relatively more frequent in "daarker" habitats. Predation by birds is not known to occur and rodent predation in winter or genetic drift cannot explain the observed correlations. Habitats differ in their microclimate and it is suggested that climatic selection is important. Differences in morph frequencies between juvenile and adult snails support this view.