An investigation to determine variation in marsh orchid (Dactylorhiza) populations at Moses Gate Country Park, Bolton

Christine Crompton 0 1 0 Supervisor: Frank Goodridge, University of Bolton , Bolton, UK 1 University of Bolton , Bolton, UK In June 2006, two populations of Dactylorhiza were examined at Moses Gate Country Park, in Greater Manchester, to determine whether variation exists between the two populations. Careful measurements of orchid characteristics were taken at both sites, in addition to soil pH recordings, and the results compared and tested for significance using one-way ANOVA and Chi-square significance tests. Descriptive statistics and box-plots showed that there were indeed differences in orchid height, leaf width and leaf number between the two populations, with one-way ANOVA confirming their significance as P , 0.001 for all the variables. Further analyses using frequency data and Chi-square tests also showed that there were significant variations in spur size, leaf type, labellum shape and petal colour between the two sites with P , 0.001 for all these characteristics. Soil pH data were also analysed and tested using one-way ANOVA which showed that there were significant variations in soil pH levels at both sites with P , 0.001 for this data. It was concluded that there were indeed significant differences between the two populations of Dactylorhiza at Moses Gate Country Park, therefore the null hypothesis was rejected. It was suggested that further investigations could be undertaken at this site, using similar methods, over a number of years, to support this study and to provide further constructive information on the status of the two populations of orchids, which may increase the conservation value of the site. - According to Stace,1 eight main species of Dactylorhiza can be found growing in Britain, however, Dactylorhiza are notoriously difficult to identify due to extreme variation in colour and morphology within each species and because hybridization occurs readily between the species, leading to many sub-species. Only the rare Dactylorhiza lapponica, (The Lapland marsh orchid) is included in Schedule 8 of the Wildlife and Countryside Act of 1981,2 but all the Dactylorhiza orchids could be considered endangered because many of the species have declined in recent years, due to land drainage and agricultural improvements. Because of the complex variation within the Dactylorhiza genus, plant scientists are increasingly interested in studying the patterns of diversity within Dactylorhiza, in order to set conservation priorities for these orchids. Most studies focus on: identifying populations using morphological data3 or allozyme data;4 comparing abundant and threatened populations;5 studying Dactylorhiza reproductive strategies6 and identifying the optimal survival conditions for these orchids.7 The preferred habitats of Dactylorhiza are calcareous fens and marshes in wet meadows on alkaline soils. It avoids dry or acidic soils, but is capable of colonizing waste ground and abandoned industrial sites. Pollination occurs via insects such as the Cuckoo bee, beetles (Dascillus cervinus), Skipper butterflies and the female Red-tailed bumblebee. Seed-set is efficient or moderately efficient and plants divide vegetatively to form clumps.8 In the Greater Manchester area, Dactylorhiza can often be found growing in abandoned industrial sites or in regener ated Local Nature Reserves. One such reserve, Nob End (grid reference is given in the Methods section), can be found in Moses Gate Country Park in Bolton. Nob End was designated as a Site of Special Scientific Interest (SSSI) in 2000 because of its unique wildlife. The site is a regenerated industrial area that has a very high pH waste alkali deposit from the Leblanc process, the production of alkali, which was used in soap making. These processes have created an environment rich in flora, not usually found in the Greater Manchester area. One of the many taxa found in this area is the genus Dactylorhiza including the northern marsh orchid (Dactylorhiza purpurella), the early marsh orchid (D. incarnata), the southern marsh orchid (D. praetermissa) and the common spotted orchid (D. fuchsii).9 After liaising with the Park Rangers at Moses Gate it was revealed that for unknown reasons, the Dactylorhiza orchids growing in the Nob End area have been in decline for several years. However, recently, a second, rather abundant population has colonized an area known as Red Bridge (grid reference is given in the Methods section). The Rangers are unsure as to why this has happened because the area is not part of an industrial waste tip, but it has been suggested that building work in the area disturbed the soil a few years ago, altering the conditions of the soil at the site. On this basis and in order to determine whether the Dactylorhiza population at Nob End is similar in species composition to the Dactylorhiza population at Red Bridge, an investigation was initiated in June 2006. Similar ecological comparisons of threatened and abundant Dactylorhiza orchid populations were undertaken in Finland in 1994 and the results used to identify the conditions that were affecting the orchids; these included the effects of modern forestry and land drainage.5 For the purposes of this study data were collected to test the following hypothesis: There will be no variation between the population of Dactylorhiza at Red Bridge and the population of Dactylorhiza at Nob End, therefore the two populations will be made up of similar species with similar traits. Materials and methods In June 2006, data were collected from Dactylorhiza populations at Red Bridge (Ordnance Survey Grid Ref: SD745 067) and Nob End (Ordnance Survey Grid Ref: SD749 064) within the park. Several hundred morphological measurements were taken from each site using the criteria set out by Stace.1 These included qualitative data such as spur size, leaf type and labellum shape, which are all indicators of species type. Petal colour was determined using Dulux paint charts FV6, RV6, RR1 and WR3 collected from DIY stores in May 2006. Although colours are usually cross-referenced to British Standards (BS381C, 1996), time did not allow for this. Quantitative data such as plant height, leaf number and leaf width data were also collected and both sets of data were used to identify any similarities or differences within and between the two populations. Soil pH recordings were also taken at both sites to determine whether there were any similarities or differences in soil pH between the two sites. Labellum shape was determined using illustrations taken from Stace,1 and used to identify similarities in the labellum shapes of orchids at both sites and to infer species composition. The data were then recorded on a data collection sheet. The practical recordings commenced at the Red Bridge site which was measured out and divided into seven sections measuring 14.5 m 10 m. It was decided that 20 orchid plants and 2 soil pH recordings from each section would provide enough data for (...truncated)