Rekindling an old flame: A haploid model for the evolution and impact of flammability in resprouting plants

Using a two-locus diallelic population genetic model, we studied the evolut ion and impact of flammable traits in resprouting plants. A flammability lo cus' determines the flammable character of a plant and the frequency of all eles at this locus affects the probability that any plant in the population will burn. A linked 'disturbance locus' determines how a plant fares in th e presence or absence of fire. Thus, the frequencies of alleles at the flam mability locus influence evolution at the disturbance locus. The evolution of flammability-enhancing alleles is influenced by asymmetries in the genot ypic fitnesses as well as by the base flammability of the population and th e genetic structure of the system (with tighter linkage increasing the poss ibility that the population becomes more flammable). We demonstrate that st able polymorphisms of plants differing in flammability alleles are possible . The magnitude of the organism's impact on the flammable character of the environment influences where such polymorphisms are expected. Furthermore, predictions concerning the evolution of alleles at the disturbance locus ba sed solely on fitness asymmetries may fail due to the influence of plants o n their environment. Unusual population dynamics, including stable and unst able cycles of genotypes, are also presented. The relation of this model to the Mutch hypothesis and the recently developed theories of 'niche constru ction' and 'ecosystem engineering' is discussed.