Professor Simon Hiscock, Oxford Botanic Gardens and Harcourt Arboretum, Oxford
Mating systems, hybridization and polyploidy as drivers of continuing evolution in plants
Interspecific hybridisation and polyploidy are important processes in plant evolution and frequently combine in the form of allopolyploidy, the most widespread form of ‘abrupt speciation’ in plants. The relationship between hybridization and polyploidy and mating systems is well documented: outcrossing promotes hybridization, and polyploidy is frequently associated with selfing and/or apomixis. Interaction between these processes often leads to complex patterns of genetic divergence and taxonomic difficulty, as seen in certain genera of the Asteraceae, Rutaceae, Brassicaceae and Rosaceae. In Europe, ragworts (Senecio, Asteraceae) and whitebeams (Sorbus, Rosaceae) provide text book examples of taxonomic complexity associated with ongoing evolution driven by mating system variation, hybridization and polyploidy. In the UK ~5 new Senecio taxa and at least 12 new Sorbus taxa have arisen relatively recently through such processes. In this seminar I will review our studies of genetic/genomic divergence and speciation in Senecio and Sorbus, focusing especially on the origin of the Welsh ragwort (Senecio cambrensis) and the endemic whitebeams of the Avon Gorge, Bristol.