Microgeographical variation in Littorina mariae Sacchi & Rastelli and a taxonomic consideration

In the intertidal prosobranch Littorina mariae Sacchi and Rastelli from Anglesey, Wales, there was a correlation between shell morphology and shell colour in several localities. Small (5–8 mm) and large (11–14 mm) adult shells differed in morph frequencies, lip and apex colour, and sculpturing on the periostracum, and were found in different microhabitats, the former on sandy run-off channels and the latter on exposed rock platforms. The two forms were relatively discrete over short distances where the habitats were distinct, but intergraded in all characters on intermediate habitats.
Functional aspects of this variation are discussed. These diffrrences may represent the occurrence of several taxonomic groups within L. mariae.