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Title: Investigating the variability in Phragmites australis (Cav.) Trin. ex Steudel in wetlands for habitat enhancement and water treatment
Author: Keegan, Margaret Anne
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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The aims of this research were to investigate the breeding system, seed set, Ploidy levels and the extent and arrangement of genetic variation (detected as both neutral and adaptive traits) among British populations of P. australis. Significant differences in seedset and germination rates were found amongst populations. Seedset was reduced by the presence of Claviceps purpurea infection and was positively associated with mean maximum October temperature (when seed maturation occurs) and site size (possibly a proxy measure of genotypic diversity). All populations, apart from two northerly populations, had > 50% germination rate and germination rate was found to increase with increasing seedset. Microsatellite analysis was used to estimate clone structure, genetic variability within and among populations and the outcrossing rate. Substantial genetic differences in morphology were found among but not within natural British populations of P. australis. Shoot height and number of shoots showed consistent variation among populations. Under nutrient-stressed conditions, northern populations produced longer shoots than southern ones whilst the opposite was true in full-nutrient conditions. Application of synthetic sewage resulted in a marginal significant decrease in the number of shoots produced per population and an increase in below ground biomass compared to populations not receiving treatment. A further aim of this study was to assess the intraspecific variation in the effectiveness of P. australis in nutrient removal from constructed wetland systems (CWSs). Mini-CWS (~ 70 | volume) were created using five British P. australis populations and their efficacy in removing NH4-N, NO3-N, P and BOD over a one-year period was compared. There were significant and substantial differences in NH4-N removal between populations in the CWSs: a difference of 40% was found between the highest and lowest removal rates. This was most likely attributed to genetic differences among populations. From the results of this research, the main recommendations for reedbed establishment and conservation were that seeds should be collected from large reedbeds with high clonal diversity. To prevent the loss of genetic diversity over time in established reedbeds, anthropogenic disturbance should be encouraged to promote sexual recruitment. Where populations are monoclonal, and seedset is depauperate, seedlings would need to be planted from an external source. The source of P. australis could be important for CWS performance, particularly in the removal of NH4-N, suggesting that source of P. australis should be taken account of in CWS design and construction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available