Variation without mutation

MJ Wilkinson & J Warren

Sexual reproduction typically maintains a continuum of genetic variation between members of a species and this variability provides insurance against environmental change. For sessile organisms such as plants, however, outcrossing comes at the cost of reducing reproductive assurance. Many species have consequently adopted a mixed mating system or an inbreeding strategy for seed production. Inbreeding has the effect of reducing genetic variation between populations but generally maintaining variation between populations. Apomixis (agamospermy or vegetative apomixes) represents the extreme end of this spectrum of breeding strategies and since it circumvents genetic recombination generated by meiosis, it leads to the formation of genetically invariant species or microspecies. For this reason apomictic species are genetically invariant and so seemingly less able to accommodate change. This renders them vulnerable to the effects of global climate change, even though some species aggregates are apparently widespread. Indeed, despite a lack of genetic variation, most apomictic species are able to adjust there appearance and development. This variation (phenotypic plasticity) is mediated through the control of gene expression by a process known as epigenetics. The aim of this project is to characterise the extent and nature of epigenetic control exercised by UK species operating different forms of apomixis. Candidates species include Festuca vivipara and Elodea canadensis (vegetative apomixis), Rubus fruticosus (facultative pseudogamous agamospermy) Taraxacum , Limonium, Hieraceum, Sorbus (various forms of obligate agamospermy). The study will describe how changes in DNA methylation profiles associate with capacity to change development or phenotype.