XVI International Botanical Congess

L5L 1C6 One model for speciation and clonal divergence among phytopathogenic fungi invokes host jumps followed by asexual reproduction, then perhaps selective sweeps, and in some cases, loss of sex. Alternative models could start with ecological adaptations affecting pathogen phenology in response to local or regional environmental conditions. To test these and other possible factors driving divergence in populations and speciation, we compiled a data set for 13 population samples of Sclerotinia sclerotiorum, a haploid filamentous ascomycete, and 11 additional closely related species based on DNA sequence polymorphisms for 5 protein encoding genes, one anonymous region and the IGS of the nuclear ribosomal repeat, in total spanning 6500 bp. Both phylogenetic and coalescence-based approaches are used to reconstruct mutational and recombinational history. Templeton's inference key is used to determine probabilities in nested haplotypes for alternative factors resulting in phylogeographic divergence.