Lecanosticta acicola is a heterothallic ascomycete that causes brown spot needle blight on native and nonnative Pinus spp. in many regions of the world. In this study we investigated the origin of European L. acicola populations and estimated the level of random mating of the pathogen in affected areas. Part of the elongation factor 1-α gene was sequenced, 11 microsatellite regions were screened, and the mating type idiomorphs were determined for 201 isolates of L. acicola collected from three continents and 17 host species. The isolates from Mexico and Guatemala were unique, highly diverse and could represent cryptic species of Lecanosticta. The isolates from East Asia formed a uniform and discrete group. Two distinct populations were identified in both North America and Europe. Approximate Bayesian computation analyses strongly suggest independent introductions of two populations from North America into Europe. Microsatellite data and mating type distributions indicated random recombination in the populations of North America and Europe. Its intercontinental introduction can most likely be explained as a consequence of the movement of infected plant material. In contrast, the spread of L. acicola within Europe appears to be primarily due to conidial dispersion and probably also ascospore dissemination.

1st and fourth authors Department of Forest Protection and Wildlife Management Faculty of Forestry and Wood Technology Mendel University in Brno Brno 613 00 Czech Republic

fifth author Department of Forest and Soil Sciences University of Natural Resources and Life Sciences Vienna 1190 Austria

second and seventh authors Department of Genetics Forestry and Agricultural Biotechnology Institute University of Pretoria Pretoria 0002 South Africa

sixth author Department of Botany and Zoology Faculty of Science Masaryk University Brno 625 00 Czech Republic

third author Facultad de Ciencias Forestales UANL Nuevo León 67700 Mexico

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