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Ecological Genetics of Cepaea nemoralis in the French & Spanish Pyrenees: Investigating evolutionary stasis

Cepaea nemoralis is a colourful land snail found throughout north-western Europe. Natural selection by the climate and birds plays a significant role in the frequency variation of shell coloration genes. Enzyme and DNA polymorphism, together with the snail's ecology, have all been well studied too, making Cepaea a valuable model for investigating evolution in the wild.

The land snail, Cepaea nemoralis

Phase II of a long-term project on Cepaea nemoralis is underway: studying a hybrid zone between enzymatically distinct geographical areas in the central Pyrenees, at 25 year intervals. Currently, we are testing the idea that rehybridization between diverging populations is an important mechanism for maintaining evolutionary stasis on geological time scales through the mechanism of temporary hybrid advantage.

Vallée du Lys, French Pyrenees
Looking SW to Pic de Maupas (3109m)

The phenomenon of 'evolutionary stasis' (that of remaining unchanged over surprisingly long periods of time) is shown by most living creatures. Understanding its causes will illuminate better what happens at transition points, and help us discover why the tree of life is not the smooth branching pattern it was once thought to be.

Darwin 1859

Eldredge & Gould 1972
The pattern of life