Proof of ectomycorrhizal status ofSistotrema confluensPers., the type species of the polyphyletic genus Sistotrema

The genus Sistotrema is supposed to be polyphyletic. This idea is supported by the existence of saprotrophic and ectomycorrhizal Sistotrema species.We show for the first time that the type species Sistotrema confluens Pers. is ectomycorrhizal by ITS rDNA sequence identity of fruiting bodies and underneath growing ectomycorrhizas. The accompanying anatomical description of the ectomycorrhiza is in correspondence with previously published descriptions of Sistotrema ectomycorrhizas, especially the presence of ampullate hyphae. The ectomycorrhizal status and the deviating fruiting body morphology (partially stipitate versus resupinate in all other Sistotrema species) indicate a relationship of S. confluens to the ectomycorrhizal genus Hydnum. A phylogram of ITS rDNA sequences cannot resolve the basal polytomies in the genus Sistotrema but confirms the monophyly of the genus Hydnum. Thus, S. confluens is not more closely related to Hydnum than to ectomycorrhizal Sistotrema species. The proof of the ectomycorrhizal status of S. confluens can be of value in a future revision of phylogenetic relationships within the group of Hydnum and ectomycorrhizal Sistotrema species.