Research in plant evolutionary genetics aims to understand the genetic and genomic basis of adaptation and speciation in three ‘model’ systems: Senecio, Sorbus , and Orobanche. Within the genus Senecio (ragworts) speciation processes have been driven by hybridization and polyploidy. We are particularly interested in the genomic basis of adaptive divergence and speciation in the recently formed homoploid hybrid species Senecio squalidus (Oxford Ragwort) and the allopolyploid species Senecio cambrensis (Welsh Ragwort). In the genus Sorbus (Whitebeams, Rowans, and Wild Service Trees) hybridization and polyploidy have also been critical agents of genetic divergence and speciation but unlike Senecio reproduction in newly formed divergent Sorbus taxa is primarily asexual (apomixis) rather than sexual. Our Sorbus research focuses on the origin and continuing evolution of Sorbus within the Avon Gorge near Bristol (a Sorbus diversity ‘hotspot’), where at least six novel endemic taxa have evolved relatively recently. In the holoparasitic angiosperm genus Orobanche (Broomrapes) genetic divergence and associated taxonomic complexity has not been associated with hybridization and polyploidy, instead shifts in host preference and adaptation to a new host appear to be the driving force for genetic divergence and speciation. To test this hypothesis we are studying genetic divergence and assaying host preference and parasite fitness in taxa within the Orobanche minor complex.
Research in plant reproductive biology focuses on the molecular genetic and biochemical basis of pollen-stigma recognition and subsequent molecular interactions between pollen and pistil. Many flowering plants have self-incompatibility (SI) systems that prevent self-fertilization and fertilizations between genetically related individuals. SI involves molecular recognition events between pollen and stigma that determine whether a pollination event will produce seed (compatible) or not (incompatible). SI is usually regulated by a single genetic locus, S, with many allelic (haplotypic) forms. Different forms of SI have evolved many times during angiosperm diversification and so far three different molecular mechanisms have been identified. We are studying the molecular basis of pollen-stigma recognition and sporophytic SI in Senecio squalidus (Oxford ragwort), a member of the Asteraceae (daisy) family, which has a different molecular mechanism of SI to the three mechanisms so far identified in other families. We also study the population genetics of SI in S. squalidus and its relatives on Mt Etna (Sicily) to determine the number, frequency and dominance relationships among S alleles in populations and the effect of S. squalidus' introduction to the UK from Sicily in the late 17th century on these parameters. In collaboration with colleagues at the University of the West of England and Estación Experimental del Zaidín in Grenada, Spain we are also investigating the role of reactive oxygen species (ROS) and nitric oxide (NO) in pollen-stigma interactions using a range of different angiosperms including Senecio, Arabidopsis, and olive (Olea europaea).