Harrington DEB9870675 Recognition of fungal species and a better understanding of their evolution are needed. For example humans move plant pathogenic fungi around the world on their crops and plant products, often with devastating consequences. Introductions of new pathogens and changes in fungal populations frequently frustrate disease control strategies, reduce food and fiber productivity, and threaten forest ecosystems. In fact human dispersal even may be greatly accelerating the rate of evolution of many plant pathogens. Ceratocystis species, which are primarily found in the Americas, have been particularly damaging when introduced into new ecosystems or when introduced plant hosts come into contact with indigenous pathogen populations. The limited morphological variation within Ceratocystis may reflect constraints associated with dependency on non-specific insects for dissemination, and physiological adaptation to new hosts may have been the driving force in speciation of these fungi. Dr. Harrington, a recognized expert on the group will delimit species within the genus using a broader array of criteria than traditionally has been used: morphology, interfertility tests, physiology, and phylogenetic analyses of DNA sequences of ribosomal and mating type genes. Nuclear and mitochondrial DNA fingerprinting will be used to identify genetic diversity of populations and distinguish indigenous populations (high diversity) from introduced populations (limited diversity due to genetic bottlenecks). In addition Ceratocystis has many different reproductive strategies, perhaps the most complex array identified in a fungal group, and work on the molecular basis of the mating systems will continue. Evolution of mating systems and host specialization will be traced through the phylogenetic schemes developed through DNA sequence analysis. These works will build a foundation for systematic treatment of this ecologically important genus and allow for a more practical definition of species in t he fungi.
