title: Spore sensitivity to sunlight and freezing can restrict dispersal in wood-decay fungi.
abstract: Assessment of the costs and benefits of dispersal is central to understanding species' life-history strategies as well as explaining and predicting spatial population dynamics in the changing world. While mortality during active movement has received much attention, few have studied the costs of passive movement such as the airborne transport of fungal spores. Here, we examine the potential of extreme environmental conditions to cause dispersal mortality in wood-decay fungi. These fungi play a key role as decomposers and habitat creators in forest ecosystems and the populations of many species have declined due to habitat loss and fragmentation. We measured the effect of simulated solar radiation (including ultraviolet A and B) and freezing at -25°C on the spore germinability of 17 species. Both treatments but especially sunlight markedly reduced spore germinability in most species, and species with thin-walled spores were particularly light sensitive. Extrapolating the species' laboratory responses to natural irradiance conditions, we predict that sunlight is a relevant source of dispersal mortality at least at larger spatial scales. In addition, we found a positive effect of spore size on spore germinability, suggesting a trade-off between dispersal distance and establishment. We conclude that freezing and particularly sunlight can be important sources of dispersal mortality in wood-decay fungi which can make it difficult for some species to colonize isolated habitat patches and habitat edges.
authors.affiliation: Department of Biosciences, Metapopulation Research Centre, University of Helsinki P.O. Box 65, FI-00014, Helsinki, Finland ; Marine Research Centre, Finnish Environment Institute P.O. Box 140, FI-00251, Helsinki, Finland.
authors.forename: Veera
authors.initials: V
authors.lastname: Norros
authors.affiliation: Department of Biosciences, Metapopulation Research Centre, University of Helsinki P.O. Box 65, FI-00014, Helsinki, Finland.
authors.forename: Elina
authors.initials: E
authors.lastname: Karhu
authors.affiliation: Natural History Museum, University of Oslo P.O. Box 1172 Blindern, NO-0318, Oslo, Norway ; Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo P.O. Box 1066 Blindern, NO-0316, Oslo, Norway.
authors.forename: Jenni
authors.initials: J
authors.lastname: Nordén
authors.affiliation: Department of Environmental Sciences, University of Helsinki P.O. Box 65, FI-00014, Helsinki, Finland.
authors.forename: Anssi V
authors.initials: AV
authors.lastname: Vähätalo
authors.affiliation: Department of Biosciences, Metapopulation Research Centre, University of Helsinki P.O. Box 65, FI-00014, Helsinki, Finland.
authors.forename: Otso
authors.initials: O
authors.lastname: Ovaskainen
keywords: Basidiomycetes; connectivity; germination; habitat fragmentation; life-history evolution; long-distance dispersal; mortality; movement; spore viability; stress tolerance; ultraviolet radiation