Contrasting diversity patterns of brown: and white-rot wood saprotrophs in response to climate and dispersal vectors

Climate is a major determinant of fungal diversity on both large and small spatial scales. However, little is known about the combined effects of regional temperature, microclimate, and dispersal vectors on fungal diversity. We studied the effect of microclimate and wood-inhabiting beetles serving as potential dispersal vectors on the diversity of wood-inhabiting fungi in general-and of brown- and white-rot fungi in particular-along a regional temperature gradient. This focus is motivated by the critical role that different rot types play in wood decomposition and carbon cycling. Beetle and fungal communities were sampled in 243 logs of Norway spruce (Picea abies), which were placed along a 1200 km latitudinal gradient in Sweden (i.e. regional temperature gradient) and under different shading conditions (i.e. microclimatic gradient). Species richness of brown-rot fungi increased with beetle abundance in both the south and the north, whereas shade level markedly limited their species richness only in the north. In contrast, white-rot fungi were unaffected by either factor. These findings highlight that fungal responses to microclimate and dispersal vectors may differ between regions and suggest that species richness of brown-rot fungi may increase with a warming climate, especially in the north.