Colour and Banding Morphs in Subfossil Samples of the Snail Cepaea
Since Ford’s careful definition (1940) of polymorphism, the interest to population geneticists and evolutionists of this remarkable and widespread phenomenon needs no emphasizing. Its interest is enhanced when studies of its stability or otherwise can be made over long periods of time. The late Cyril Diver realized the importance of subfossil snail shells for this purpose as long ago as 1929. Currey & Cain (1968), using Cepaea nemoralis (L.) and C. hortensis (Müller), two species with an extensive shell-character polymorphism, were able to show a considerable alteration in southern England in the proportions of the bandless form in C. nemoralis from the hypsithermal (c. 4500 BC) to the present day, consistent with climatic selection; C. hortensis, however, showed no consistent signs of change. They showed also in C. nemoralis that the type of geographical distribution of morph frequencies which they called area effects (Cain & Currey 1963a) was probably more widespread in pre-Iron Age times than now, and some area effects may have lessened in intensity. They were able to give considerable evidence concerning these changes for a district including the western Marlborough Downs and the lowlying country adjacent, which is famous for its antiquities and in which several important excavations have taken place.
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- Arnold R.W. (1966) Factors affecting gene-frequencies in British and continental populations of Cepaea. D. Phil, thesis, Oxford.Google Scholar
- Cain A. J., Cameron R. A. D. & Parkin D. T. (1969) Ecology and variation of some helicid snails in northern Scotland. Proc. malac. Soc. Lond. 38, 269–299.Google Scholar
- Cameron R. A. D. (1969a) The distribution and variation of Cepaea nemoralis L. near Slievecarran, County Clare and County Galway, Eire. Proc. malac. Soc. Lond. 38, 439–450.Google Scholar
- Cook L. M. (1966) Notes on two colonies of Cepaea nemoralis (L.) polymorphic for white lip. J. Conch. 26, 125–130.Google Scholar
- Cook L. M. & Peake J. F. (1960) A study of some populations of Cepaea nemoralis L. from the Dartry Mountains, Co. Sligo, Ireland. Proc. malac. Soc. Lond. 34, 1–11.Google Scholar
- Cook L.M. & Peake J. F. (1962) Populations of Cepaea nemoralis L. from sand-dunes on the Mullaghmore Peninsula, Co. Sligo, Ireland, with a comparison with those from Annacoona, Dartry Mts., Co. Sligo. Proc. malac. Soc. Lond. 35, 7–13.Google Scholar
- Ford E. B. (1940) Polymorphism and taxonomy. In J.S. Huxley (ed.), ‘The New Systematics’, pp. 493–513. Oxford University Press, London.Google Scholar
- Godwin H. (1956) The history of the British flora. A factual basis for phytogeography. Cambridge University Press, Cambridge.Google Scholar
- Johnson C. G. & Smith L. P. (1966) The biological significance of climatic change in Britain. Academic Press, London.Google Scholar