Groupx+8


 * Group Members:** Jemma Brett, Robyn Emms, Sameera Khan, Harriet Duffield, Sol Franklin, Daisy Ward, Isabel Morris, Dafina Zeqiraj.

**First Draft.**


Fig 1. Snail habitat with marked sampling sites.

Collection sites: 1. Woodland. 2. Woodland. 3. Shrub area. 4. Open grassland. 5. Open grassland. 6. Shrub area.

- Up to 30 samples (alive and dead snails) will be collected at each site (as shown on the map). - All samples will be collected at ground level. - Collection sites will measure 10m in diameter. - The shell colour and number of bands will be recorded (an example of our frequency table is shown below).

Fig 2. An example frequency table.


 * Null hypothesis:** There is no significant difference in snail shell colour (and number of bands) in relation to the environment in which they are found. Any difference is due to chance.


 * Alternative hypothesis:** There is a significant difference in snail shell colour (and number of bands) in relation to the environment in which they are found.

Our aim is to determine the relationship between snail phenotype and the environment, which will therefore support or reject our null hypothesis.

**Second Draft.**
Fig 3. Snail habitat with updated collection sites.

Collection sites: 1. Woodland. 2. Woodland. 3. Shrub area. 4. Open grassland. 5. Open grassland. 6. Shrubs.

- Two samples will be taken at each level of the area to limit the variables. - Sample sites will be no less than 20 meters apart to sample separate populations with minimal gene flow. - Up to 30 samples (alive and dead snails) will be collected at each site (as shown on the map). - All samples will be collected at ground level. - Collection sites will measure 10m in diameter.

**Final Draft.**
Fig 4. Snail habitat with final draft collection sites.

Collection sites: 1. Open grassland (at the top of the hill). 2. Open grassland. 3. Open grassland. 4. Open grassland. 5. Open grassland. 6. Open grassland (at the bottom of the hill).

- We will attempt to minimise the variables by collecting samples from the same habitat but at different altitudes. - We will attempt to distinguish between genetic drift or selection by repeating the experiment on a parallel hill. - Collection sites will measure 10m in diameter (pre-cut string will be used to measure this). - Collection sites will be no less than 20m apart so that we can attempt to sample separate populations with minimal gene flow (pre-cut string will be used). - Up to 30 samples (alive and dead snails) will be collected at each site (as shown on the map). - All samples will be collected at ground level.

**Definitions.**

 * //Capaea nemoralis //**: Common names include grove snail and brown-lipped snail. It is an air-breathing terrestrial snail which is commonly found within many habitats throughout Europe. Excluding the band around the lip of the shell, //C. nemoralis// is highly polymorphic with regard to a variety of colours (yellow, pink and brown), number and intensity of bands (0, 1, 2, 3, 4, or 5) and shell height (however this polymorphism is not discussed in this experiment).


 * Gene: ** The fundamental physical and functional unit of heredity, which carries information from one generation to the next (many other definitions also available).


 * Allele: ** A variant of a gene, with different alleles resulting in different phenotypes.


 * Genotype: **Defined as the “genetic make-up” of an individual.


 * Phenotype: **The physical characteristics of an individual. Phenotypes are composed of “traits”.


 * Mutation: **In itssimplest form, a mutation is a permanent structural alteration in DNA. It is the process by which genetic variation occurs and includes; point mutations, insertions, deletions, duplication, inversion, translocation, polysomy, whole genome duplication etc.


 * Gene flow: ** The transfer of alleles or genes from one population to another.


 * Natural selection: ** The differential survival and reproduction of individuals which have differing heritable traits. In response to selection, traits that improve reproductive success will increase in frequency over time.


 * <span style="font-family: Arial,sans-serif; font-size: 10pt;">Genetic drift: **<span style="font-family: Arial,sans-serif; font-size: 10pt;"> A random change in allele frequencies due to chance factors. Happens in both small and large populations but occurs more rapidly and over a broader range of conditions in small populations. Genetic drift is the consequence of finite population size, takes place in all populations and any selection must take place against a background of genetic drift.


 * <span style="font-family: Arial,sans-serif; font-size: 10pt;">Polymorphism: **<span style="font-family: Arial,sans-serif; font-size: 10pt;"> In genetics, it is the existence of two or more forms which are genetically distinct from one another but are contained within the same panmictic population.


 * Introduction. **

<span style="font-family: Arial,sans-serif; font-size: 10pt;"><range type="comment" id="530565930_1">Ecological genetics is the study of the relationship of the mechanisms responsible for genetic variation within a natural population in relation to its environment (Jones, 1973; Richards //et al.//, 2013). </range id="530565930_1">Research in this field places an emphasis upon traits which have an ecological significance (traits which affect an organism’s survival and reproduction). It can be useful for investigating many species, including humans; however it is most easily applied to the mollusc //Capaea nemoralis//. This particular species is the ideal model system for the study of interactions between ecology and genetics as they have visible polymorphisms which have a direct, known, link between phenotype and genotype (Jones, 1973). In addition, the low mobility of most terrestrial snails results in a low dispersal rate which reduces the likelihood of populations sharing a common gene pool, thus allowing for the comparison of different populations within one area. The phenotype of empty shells can also provide a record of the genes that the animal possessed whilst it was alive, thus providing an insight into the genotypes of both alive and dead snails. These factors, as well as a vast amount of information available on its general lifestyle, make //C. nemoralis// an ideal model species for the study of ecological genetics (Jones, 1973).

<span style="font-family: Arial,sans-serif; font-size: 10pt;">The fact that populations remain polymorphic has been an area of interest for many ecological geneticists as they attempt to understand the effects of polymorphisms (Cain and Sheppard, 1954). It was originally believed that if a particular phenotype is considered advantageous over another phenotype, those individuals with the advantageous phenotype are more likely to survive and reproduce offspring which carry the advantageous alleles. On the other hand, individuals that possess the disadvantageous phenotype are less likely to reproduce, and more likely to be predated upon, so that eventually their alleles disappear from the population. However, this is not always the case as polymorphisms do remain.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Many early attempts at explaining polymorphisms indicated genetic drift, gene flow, mutations or natural selection as possible mechanisms. However, Cain and Sheppard (1954) <range type="comment" id="530565930_2">state that variation is maintained by balanced polymorphism </range id="530565930_2">but the proportions of different polymorphisms in <range type="comment" id="530565930_3">each population are affected by visual predation; thus natural selection is important</range id="530565930_3">. This suggests that several mechanisms may be responsible for the maintenance of genetic variation (Jones //et al//.,1977; Cain and Sheppard, 1954).

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Our experiment aims to determine the relationship between the relative frequencies of the //C. nemoralis// shell variants (yellow, pink or brown, as well as, banded or un-banded) in relation to the environment in which they are found. This builds upon previous work undertaken by Jones //et al//. (1977) and Cain and Sheppard (1954) by providing more evidence for the mechanisms which are responsible for the maintenance of genetic variation. <range type="comment" id="530565930_4">Throughout our experimental design, we have attempted to minimise the number of variables by collecting samples from the same habitat (open grassland) but at different altitudes, at Pulpit Hill Nature Reserve in Buckinghamshire. In addition, we have repeated the experiment, in parallel, in order to clearly distinguish between the mechanisms acting upon the polymorphisms.</range id="530565930_4">


 * <span style="font-family: Arial,sans-serif; font-size: 10pt;">Word count: **<span style="font-family: Arial,sans-serif; font-size: 10pt;"> 508 words.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Cain, A. J. and Sheppard, P. M. 1954. Natural selection in //Cepaea//. //Genetics//, **39**, 89-116.
 * <span style="font-family: Arial,sans-serif; font-size: 10pt;">References. **

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Jones, J. S. 1973. Ecological genetics and natural selection in molluscs. //Science//. **182**, 546-552. doi: 10.1126/science.182.4112.546

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Jones, J. S., Leith, B. H. and Rawlings, P. 1977. Polymorphism in //Cepaea:// A problem with too many solutions?, //Annual Review of Ecology and Systematics//, **8**, 109-143.

<span style="font-family: Arial,sans-serif; font-size: 10pt;">Richards, P. M., Liu, M. M., Lowe, N., Davey, J. W., Blaxter, M. L. and Davison, A. 2013. RAD-Seq derived markers flank the shell colour and banding loci of the //Cepaea nemoralis// supergene. //Molecular Ecology//, **22**, 3077-3089. doi: 10.1111/mec.12262