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

__Discussion __ Our experimental approach aimed to observe snail populations in lower regions of the slopes in five locations to test whether there were phenotypic differences in populations near and away from areas of vegetation. Our raw data comprising of both vegetative and non vegetative areas indicates there is no phenotypic differences in the populations of snails residing on the lower regions of the slope. Our calculated Chi X2 value for raw data collected on the lower regions of the slopes was not significant. The independent calculations of Chi X2 value for sites near and away from vegetation on the lower regions also showed no significance when compared to the critical value. The difference between observed and expected values of our results under the null hypothesis was negligible. Therefore we concluded there are no significant phenotypic differences in snail populations near and away from vegetation on the lower regions of the slopes. Vegetation is not a significant factor influencing the frequencies of phenotypes in the snail population in the lower regions. Their phenotypic inhabitancy in the region must be selected for by another favourable attribute such as the climate condition or aspect of sunlight in the region.

When observing the colour and banding pattern of the snails, we expected to find certain phenotypes at a higher frequency in the area with vegetation and others in the area without vegetation. However the experiment was limited as there are other factors which weren’t taken into account. Visual selection by thrushes means that they will predate on snails with certain characteristics such as those with less camouflage. Even stronger visual selection has been recorded on short grass (1). Therefore there is an advantage of snails being in an area of vegetation to begin with no matter what the morphology of the snail. Temperature is also a factor which has an effect upon where snail phenotypes are found. The darker shells warm up more rapidly and therefore tend to be found further north where the climate is cooler. The number of bands on the snails shells can also have an effect on the temperature they experience. When exposed to the sun, banded snails attain a higher equilibrium temperature than do un-banded (2). Previous studies have shown that the frequencies of snail phenotypes are dependent on the amount of sunlight available on different positions on a slope. We only collected data on the lower region of the slopes so it is possible that there were no significant differences due to the lack of variability in sunlight in our sample space. The nature of our evidence makes it hard to generate conclusions as we didn't take into account these factors which also play a part in the distribution of phenotypes.

It can also be argued that our results may not have been as accurate as they should have been. Firstly, the way we measured our results may not have been reliable because we simply counted snails at different positions of five different slopes and we cannot be sure that each member of the team counted at exactly the same position within those different slopes. In order to overcome this issue, we could have used a different technique such as making a grid on the field using measuring tape, generating random coordinates and putting a quadrat down in the particular position on each slope. Then we could count how many snails were found in that area and take note of the phenotypes. In order to make our experiment reliable it is essential that we conduct further research by repeating the experiment and comparing the results. It may be better to increase our sample size to reduce the possibility of sampling errors. We could also try to take into account more of the factors we discussed, such as aspect of sunlight, and try to minimize the amount of variables in our experiment.

__References: __ (1), (2) - J. S. Jones, B. H. Leith, P. Rawlings. Polymorphism in Cepaea: A Problem with Too Many Solutions? Annual Review of Ecology and Systematics, Vol. 8 (1977), pp. 109-143