The poor relation? Polymorphism in Cepaea hortensis (O. F. Müller) and the Evolution Megalab

Abstract

The shell-colour and banding polymorphism of Cepaea hortensis has attracted less attention than that of its congener C. nemoralis. While the Evolution Megalab acquired many records of its variation, those submitted by amateurs were unreliable, and hence it was impossible to analyse possible changes over time. Nevertheless, the Megalab database reveals many aspects of variation in C. hortensis. There is less polymorphism for shell colour than in C. nemoralis and the pattern of geographical variation is different; in some cases trends go in the opposite direction. Polymorphism is greatest near the centre of the range. Variation with habitat shows trends similar to those in C. nemoralis, although the absence of data on band fusions limits the extent to which such variation can be detected. While it is clear that natural selection influences morph frequencies in many cases, the differences in patterns seen in these two very similar species indicate that appearance alone does not determine the range of frequencies observed. © 2013 The Author.