The population genetics and speciation of fungi is a rapidly developing field, heavily dependent upon the use of molecular markers. No basic text exists which describes the methods employed or the findings obtained from such investigations. This book is intended to provide such an account. It describes the methodologies employed and, for the benefit of the non-mycological reader, a brief introduction to basic fungal biology. Recent findingsrelating to processes in fungal populations - mutation, migration, recombination, heterokaryosis, hybridization, polyploidy, and the operation of selective forces are combined with traditional fungal biology. Finally the taxonomic problems raised by fungal species are discussed, together with the processes of speciation.