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Genetic variation in the widespread lichenicolous fungus Marchandiomyces corallinus

     Departamento de Matemáticas y Física Aplicadas y Ciencias de la Naturaleza, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Madrid, España

Paula T. DePriest

     Botany Section, United States National Herbarium, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, DC 20013-7012

James D. Lawrey

     Department of Environmental Science and Policy, George Mason University, Fairfax, Virginia 22030-4444

The lichenicolous basidiomycete Marchandiomyces corallinus is widely distributed in North America and Europe, where it commonly is found on a variety of lichens. Theoretically either of these characteristics, a wide geographic range or generalized host ecology, could provide opportunities for genetic differentiation within this species. To determine how genetic variation is partitioned in M. corallinus, 12 fungal isolates were obtained from locations in North America and Europe; at two locations, in Washington County, Maine, and on the Isle of Mull in Scotland, fungi also were isolated from different lichen hosts. Vegetative mycelial compatibility tests were used to determine compatibility groupings from among the isolates; in addition, several PCR amplification products (RAPD, nuITS rDNA) were obtained for each isolate. A number of distinct compatibility groups were recognizable based on geography, not host ecology. In addition compatible isolates always were restricted to either North America or Europe. However RAPD markers indicated that compatible isolates are not always genetically identical. The presence of sequence heterozygosity at specific positions indicated that the isolates are heterokaryotic and a number of distinct haplotypes could be identified based on ITS variation at three separate locations. This type of genetic variation in these fungi suggests that sexual recombination is possible and that genetic differentiation has taken place recently as a result of geographic isolation, not host switching.

Key words: basidiomycetes, host-parasite evolution, lichenicolous fungi, lichens, Marchandiomyces, rDNA sequences