The mating type system of the rare polypore Hapalopilus croceus

Hapalopilus croceus is a rare, wood-decay polypore associated with old coarse broadleaf trees, primarily Quercus. It is mainly distributed throughout the temperate zone of the Northern Hemisphere with its main distribution in Europe. Mating systems in fungi influence the probability of in- or outbreeding and may affect the species' fitness. We found the mating system of H. croceus to be bipolar by pairing 18 single spore isolates from one sporocarp. We discuss this finding from the perspective of H. croceus as a threatened species with a very small and fragmented current population associated with a declining habitat and globally red-listed as Vulnerable (VU). (C) 2020 Elsevier Ltd and British Mycological Society. All rights reserved.