In recent years an international research initiative focusing on the devastating dry rot fungus Serpula lacrymans has been established. Previous research suggests that S. lacrymans provides a unique model system to study evolutionary processes and life hi story traits in basidiomycetes, including the mating and vegetative incompatibility regulation systems. The ‘genetic simplicity and transparency’ observed in S. lacrymans makes us believe that the fungus is a very suitable model organism that can be used to accumulate new knowledge in this field. We present four interrelated sub-projects, which all rest on the use of a variety of DNA techniques on a world-wide, representative sample of living culture isolates of the model organism. It has been hypothesize d that both the mating (MAT) and vegetative incompatibility (vic) loci are governed by inverse frequency-dependent selection, favoring rarer alleles or genotypes. This hypothesis will be tested. We will use computer simulations and empirical data from S. lacrymans to get an idea of evolutionary processes and forces that may influence the MAT/vic allelic diversity and persistence time. The molecular evolution of the vic/MAT alleles/idiomorphs in S. lacrymans will be studied using different approaches. We w ill use expressed sequence tags in comparing the transcriptome from different types of mycelia in the search for genes that are involved in the mating and vegetative incompatibility regulation systems. In order to study speciation processes in S. lacryman s and the sister taxon S. himantioides, we will analyse the MAT idiomorph variation and use a ‘genealogical concordance phylogenetic species recognition’ (GCPSR) concept. Another goal is to use microsatellites and vic/MAT data to analyze the phylogeograph y and population genetics of S. lacrymans. We seek funding for one PhD position (3 years) and one researcher position (3 years). In addition, four senior researchers and one private company will be involved.