Molecular systematics of 'Rhododendron ponticum' L. and its close allies

Rhododendrons;Rhododendrons--Great Britain

Milne, Richard I. ; Abbott, Richard J. ; Abbott, Richard J.

University:University of St Andrews

Department:Biology (School of)

关键词: Rhododendrons;    Rhododendrons--Great Britain;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/2830/RichardIanMilnePhDThesis.pdf?sequence=3&isAllowed=y

来源: DR-NTU

【 摘 要 】

Rhododendron ponticum, introduced to the British Isles in 1763, hasbecome a noxious invasive pest species, particularly in the west.Material of R. ponticum and its close allies in subsection Pontica weresubjected to chloroplast DNA RFLP analysis. A preliminary phylogeny basedon all cpDNA variation detected is presented. Suggestions regarding theinterrelationships of these species are made, and a cpDNA-type of unknowntaxonomic identity is tentatively identified.Chloroplast DNA differences were detected between native material ofR. ponticum from Turkey, Spain and Portugal. Based on these differences, itwas determined that approximately 90% of material naturalised in the BritishIsles originates from Spain and 10% from Portugal. These two types ofmaterial occur in roughly the same proportion throughout the British Isles.About 10% of naturalised accessions were found to contain an rDNAmarker indicating nuclear introgression from R. catawbiense. Introgressedindividuals are shown to be most common in the coldest region of the BritishIsles surveyed, i.e. E. Scotland, and it is suggested that introgression from R.catawbiense may confer increased frost tolerance to R. ponticum. Theoccurrence of the rDNA marker was not correlated with that of morphologicalmarkers indicating introgression. Correlations were found betweenmorphological characteristics, which may result from introgression fromcultivated species, such as R. maximum. Molecular evidence for theinvolvement of R. maximum in the ancestry of British R. ponticum wasfound in two accessions which resembled R. maximum. in certainmorphological characteristics. It was established that another unidentifiedspecies was involved in the parentage of naturalised material.Five natural hybrid combinations amongst Turkish Rhododendronspecies were detected using morphological, cpDNA and nuclear rDNAmarkers. These were R. ponticum x R. ungernii, with introgression in bothdirections; R. ponticum x R. smirnovii; R. smirnovii x R. ungernii withintrogression at least towards R. ungernii; R. smirnovii x R. caucasicum; andR. ponticum x R. caucasicum. The unusual characteristics of the lastcombination are discussed in some detail.