Disentangling cryptic species in the Marasmius haematocephalus (Mont.) Fr. and M. siccus (Schwein.) Fr. species complexes (Agaricales, Basidiomycota)

Marasmius haematocephalus (Mont.) Fr. and M. siccus (Schwein.) Fr. (ser. Haematocephali) were respectively described from Southeastern Brazil and from Eastern United States, and subsequently reported as pantropical and pantemperate. Recent phylogenetic studies indicate that these two species are closely related in their broad concepts and at least M. haematocephalus is suggested to be a species complex. We evaluated herein whether M. haematocephalus is or is not pantropical and whether M. siccus is or is not pantemperate. Combined nrITS + nrLSU and nrITS + rpb2 + ef1-α phylogenies were reconstructed using Maximum Likelihood and Bayesian analyses and integrated with detailed morphological data. Results indicated that M. haematocephalus ‘sensu stricto’ (s. str.) is at most Neotropical, with closely related species in Tropical Africa and Indo-Malay. Similarly, M. siccus s. str. is at most Nearctical, with closely related species in the temperate Palearctic. For the time being, one can recognize about 23 species in the M. haematocephalus and M. siccus complexes, of which four are described as new herein.