An investigation of local adaptation in the model plant species Arabidopsis thaliana

Species extinction rates are causing alarm. Anthropogenic distortion of the climate system is rapidly altering the natural environment. Arabidopsis thaliana is a model species in molecular biology with widespread wild populations showing functional diversity however its ecology and evolution is poorly understood. Faced with a changing natural world, what is the adaptive potential of the model plant species Arabidopsis thaliana? This thesis focuses on the interactions of genotypes, phenotypes and environments to assess the current state of adaptation in this vagile species and to identify mechanisms for rapid adaptation to future stress, focusing on plant pathogens. Here I show that A. thaliana populations in England exhibit evidence of local adaptation and genetic structure. A large common garden experiment using genotypes gathered in natural habitats revealed functional fitness differences in genotype-by-environment interactions. Wild populations showed differential representation of RPM1 alleles suggesting non-random processes are responsible for the exhibited patterns. A further common garden experiment demonstrated ‘home site advantage’ through a correlation between fitness and home site climate, which suggests that local adaptation had occurred. Phenotypic plasticity and mechanisms for rapid adaptation could be essential for plant survival under predicted climate change. Using Xanthomonas spp. as xenopathogens, I show differing levels of pre-adaptation for pathogen response exists in wild UK populations of A. thaliana. By using a multi-generation study, I found some evidence that epigenetic modification enabled rapid adaptation to pathogen stress. Finally, I compared the metabolic expressions of phenotype among genotypes in two artificial environments. Environmental effects detected by this method are far greater than genetic ones, suggesting that metabolic plasticity can underpin environmental adaptation. Taken together, my results suggest that wild populations of A. thaliana contain a range of mechanisms for rapid adaptation to environmental change. If these capacities are general, my work offers a note of optimism about the fate of some wild plant species in the face of global climate change. Additionally, as A. thaliana is a model species in genomics, my findings may facilitate future exploitation of these traits by crop geneticists.