Intro+-+Ishara,+Rachelle,+Lulu,+Odeliya,+Soshi+&+Moneeba

**__Group Members: __**
====Capaea nemoralis is a common and widespread snail species in Western Europe. It has been the subject of much study due to the fact that its populations show differences in shell background colour, number of bands and several other features. Evolutionary biologists have been eager to study this snail as its shell pattern is highly polymorphic and simply inherited. This is ideal for obtaining evidence of the mechanisms that act on the frequency of a certain phenotype, such as genetic drift, gene flow and selection. ====
 * **Ishara Anees**
 * **Myriam Haltalli**
 * **Shoshi Weisman**
 * **Odeliya Dadoune**
 * **Lulu Mohammed**
 * **Moneeba Meer**

====Cameron and Pokryszko (2008)[i] studied the variation in Cepaea populations for close to half a century. They observed Cepaea hortensis, which live in Hertfordshire (UK). They found that although the general pattern of shell colour and banding polymorphism remained stable, there was a clear trend for a reduction in the frequency of yellow shells at sites from the bottoms of hills. They recorded that this relationship stopped in 2007. It was concluded that climate fluctuations destroyed this relationship. ====

====Another study was conducted on Cepaea hortensis, this time in Western France. This experiment, conducted by Le Mitouard et al (2010)[ii] observed the relationship between the polychromatic nature of the snails’ shells, and the gradient of the landscape on which they inhabited. Similar to our experiment, the landscape they observed was zones from low to high vegetation densities, in particular, hedgerows. Amongst their findings was that at high hedgerow density the significant spatial structure they discovered was a balance between local genetic drift and environmentally controlled gene flow. The pattern they found showed that isolation due to distance resulted from direct gene exchange between neighboring populations. ====

====A study by Cook (2005) [iii]  found evidence to suggest that selection favours combinations of common morphologies (whatever they are for that location). The indication is that selection has caused these combinations to become common. This is consistent with the idea that populations of Cepaea hortensis are subject to various selection pressures - depending on the time and place - which act on the phenotype of the snail. Cook concluded that such selection could lead to prolonged polymorphism. ====

====Our experimental approach will involve observing five sample spaces near regions of specific vegetative areas and five sample spaces away from vegetative areas to collect information on divergent snail populations. Each sample space will be <range type="comment" id="26626">replicated five times to ensure any significant difference within the data is not due to sampling errors. The samples will be collected at similar altitudes, facing the same aspect – on the lower parts of the slopes – in order to limit the variables acting on each sample population. We will aim to collect data for at least 30 snails at each site and we hope to examine the colours and the banding patterns of the shells in both adult and sub-adult snail species. The observations we will make will allow us to analyse whether there are significant phenotypic differences within each population and later determine <range type="comment" id="650903">whether they are due to genetic drift, gene flow or selection. ====

====<span style="font-family: Calibri,sans-serif;">[i]Cameron, R. and Pokryszko, B. (2008) Variation in Cepaea populations over 42 years: climate fluctuations destroy a topographical relationship of morph-frequencies, <span style="font-family: 'Calibri Italic',serif;">Biological Journal Of The Linnaean Society, <span style="font-family: Calibri,sans-serif;">95(1), p.53-61. ==== ====<span style="font-family: Calibri,sans-serif;">[ii]]]Le Mitouard, E. et al.(2010) Spatial structure of shell polychromatism in Cepaea hortensis in relation to a gradient of landscape fragmentation in Western France, <span style="font-family: 'Calibri Italic',serif;">Landscape Ecology , <span style="font-family: Calibri,sans-serif;">25(1), p.123-134 ==== ====<span style="font-family: Calibri,sans-serif;">[iii]Cook, L. (2011) Disequilibrium in some Cepaea populations, <span style="font-family: 'Calibri Italic',serif;">Heredity, <span style="font-family: Calibri,sans-serif;">94(5), p.497-500 ====