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|Title: ||Molecular systematics of 'Rhododendron ponticum' L. and its close allies|
|Authors: ||Milne, Richard Ian|
|Supervisors: ||Abbott, Richard J.|
|Issue Date: ||1998|
|Abstract: ||Rhododendron ponticum, introduced to the British Isles in 1763, has
become a noxious invasive pest species, particularly in the west.
Material of R. ponticum and its close allies in subsection Pontica were
subjected to chloroplast DNA RFLP analysis. A preliminary phylogeny based
on all cpDNA variation detected is presented. Suggestions regarding the
interrelationships of these species are made, and a cpDNA-type of unknown
taxonomic identity is tentatively identified.
Chloroplast DNA differences were detected between native material of
R. ponticum from Turkey, Spain and Portugal. Based on these differences, it
was determined that approximately 90% of material naturalised in the British
Isles originates from Spain and 10% from Portugal. These two types of
material occur in roughly the same proportion throughout the British Isles.
About 10% of naturalised accessions were found to contain an rDNA
marker indicating nuclear introgression from R. catawbiense. Introgressed
individuals are shown to be most common in the coldest region of the British
Isles surveyed, i.e. E. Scotland, and it is suggested that introgression from R.
catawbiense may confer increased frost tolerance to R. ponticum. The
occurrence of the rDNA marker was not correlated with that of morphological
markers indicating introgression. Correlations were found between
morphological characteristics, which may result from introgression from
cultivated species, such as R. maximum. Molecular evidence for the
involvement of R. maximum in the ancestry of British R. ponticum was
found in two accessions which resembled R. maximum. in certain
morphological characteristics. It was established that another unidentified
species was involved in the parentage of naturalised material.
Five natural hybrid combinations amongst Turkish Rhododendron
species were detected using morphological, cpDNA and nuclear rDNA
markers. These were R. ponticum x R. ungernii, with introgression in both
directions; R. ponticum x R. smirnovii; R. smirnovii x R. ungernii with
introgression at least towards R. ungernii; R. smirnovii x R. caucasicum; and
R. ponticum x R. caucasicum. The unusual characteristics of the last
combination are discussed in some detail.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Biology Theses|
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