Diversity of wood-inhabiting fungi in woodpecker nest cavities in southern Poland

Globally, tree-holes are important ecological component of forest and woodlands. Numerous microorganisms rely on cavities, both natural and those excavated by primary cavity nesting birds, mainly by woodpeckers, for their survival and reproduction. However, the fungi occurring in cavities are not well characterized. Specifically, very little is known about the fungal communities inhabiting the woodpecker nest cavities. Therefore, in this study, we investigated the fungal diversity of cavities in southern Poland. The samples were collected from freshly excavated woodpecker nest cavities using a nondestructive method (ND). The spatial distribution of fungal communities within the cavities was evaluated by sampling different parts of a single cavity using a destructive method (D). We detected 598 fungal isolates that included 64 species in three phyla and 16 orders using the ND method. Most of the fungi isolated from the cavities represented the phylum Ascomycota (73.9% of the isolates) with 11 orders, and Microascales was the predominant order (30% of the isolates). The most common species detected was Petriella musispora, which was isolated from 65% of the cavities. A total of 150 isolates (25%) were members of Basidiomycota, with Hymenochaetales being the dominant order (16% of the isolates). The basidiomycetous fungi were isolated from 55% of the cavities. Several taxa closely related to the pathogenic fungi and associated with secondary animal infections were detected in the wood of cavities. We identified different fungal communities in the three cavity parts using the D method. The cavity entrance had more number of species than the middle and bottom parts. The results of this study advanced our current knowledge on the mycobiota in woodpecker nest cavities and provided preliminary evidence for tree cavities being the hotspot for fungal diversity.