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Title: Biology of Athyrium distentifolium and A. flexile in Scotland
Author: McHaffie, Heather
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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The Alpine Lady-fern, Athyrium distentifolium Tausch ex Opiz is found throughout the northern hemisphere. In Scotland, there is a smaller endemic form which was discovered in 1852 and has been named Newman's Lady-fern, Athyrium flexile (Newman) Druce. A. flexile is usually found with A. distentifolium. Although morphologically distinct, the taxonomic status of A. flexile has been the subject of continuing debate. This thesis aims to clarify the relationship between the two taxa. A morphometric analysis showed little overlap between the taxa for wild grown specimens. Comparisons between the spores and stomatal density showed small differences. The chromosome number was confirmed as being the same for both taxa. Gametophytes and sporophytes of both taxa grown at low nutrient levels demonstrated that the smaller A. flexile matured faster and became fertile while A. distentifolium, which is usually larger and more vigorous, remained small and infertile. The flexile taxon may therefore be an ecotype which is specially adapted to stressful environments. A. flexile is only found in a limited number of sites in the Central Highlands of Scotland which have a low-nutrient substrate. It appears it can only survive in habitats where the competition from A. distentifolium is reduced. The most significant discovery from the cultivation of spores from individuals of A. distentifolium was that some plants, when self-fertilised, produced both the flexile and distentifolium type of sporophyte. A. flexile plants always bred true when selfed. When gametophytes of A. distentifolium and flexile were given the opportunity to cross fertilise, some A. flexile gametophytes produced an A. distentifolium sporophyte. This suggests that A. flexile might be a homozygous recessive and does not justify species status.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available