Invertebrates occurring in fruiting bodies of the pathogenic tinder fungus, Fomes fomentarius (Polyporales), in the different types of Polish protected forests

Bracket fungi are usually considered as a cause of economic losses, while they also offer specific microhabitats and have an impact on biodiversity. However, to date this topic has not been sufficiently studied. The aim of this article is to show how the diversity of invertebrate communities, viz. spiders, harvestmen (Araneae, Opiliones), pseudoscorpions (Pseudoscorpionida), two groups of mites (Mesostigmata and Oribatida), springtails (Collembola), and insects (Insecta), inhabiting fruiting bodies of the tinder fungus, Fomes fomentarius, depend on specific characteristics of forests. Samples were collected in three locations: the Białowieża National Park (BNP) characterised by a high degree of forest naturalness, the Bieszczady National Park (BdNP), which was transformed by human, but has been undergoing naturalisation for several decades, and the Karkonosze National Park affected by a large-scale forest dieback in the 1980s and which for years has been under strong tourist pressure. A total of 20 fruiting bodies of F. fomentarius were collected at each location. In total, 9,821 individuals of invertebrates belonging to 204 species were extracted. The most numerous group was Oribatida (6,595 individuals classified to 106 species), while the most numerous species was Carabodes femoralis (5,216 individuals). The study sites differed in the number of species (the highest one was observed in the BdNP, 115, and the lowest one in the KNP, 88) and number of individuals (the highest one was observed in BdNP, 4,285, and the lowest one in BNP, 1,595), as well as the number of individuals per species (the highest one was observed in the BdNP, 37.26 individuals per 1 species, and the lowest in the BNP, 15.79 individuals per 1 species). A NMDS analysis revealed that the inner distribution of the samples in each of the locations was similar in the case of mountain national parks (BdNP and KNP), while the invertebrate groupings from the BNP and KNP differed the most between one another. The multilevel pattern analysis showed different, specific invertebrate species for each study sites, e.g. Carabodes subarcticus for the BNP, Friesea mirabilis for the BdNP, Oribatella calcarata for the KNP and Dendrolaelaps pini for both mountain national parks. This study shows the uniqueness of invertebrate communities inhabiting fruiting bodies of F. fomentarius and confirms the positive role of this pathogenic fungus in shaping biodiversity. Keywords: arthropods; bracket fungi; polypores; anthropopressure; natural forest