New species of Dictyonema and Cyphellostereum (lichenized Basidiomycota: Hygrophoraceae) from tropical Africa and the Indian Ocean, dedicated to the late Hildur Krog

Abstract

A small collection of lichenized fungi belonging in the Dictyonema clade from E Africa and Mauritius, tentatively identified as D. sericeum, revealed four species new to science, one in the genus Cyphellostereum and three in the genus Dictyonema s.str. Cyphellostereum bicolor from Mauritius is similar to C. imperfectum from Guatemata, but differs in the absence of a persistent white hypothallus and the less compact hyphal sheath of the fibrils, as well as the formation of resupinate hymenophores. Dictyonema album, also from Mauritius, belongs in the group of shelf-like morphotypes and is characterized within this group by very loose tufts dominated by sterile hyphae with very loosely arranged cyanobacterial fibrils. Dictyonema krogiae from Kenya is another new species in the group with shelf-like thalli and is the first species in this group known to form a distinctly layered thallus, with very compact photobiont layer, loose medulla, and more compact lower cortex. Finally, Dictyonema tricolor from Tanzania is a crustose taxon with ascending to erect tufts of densely arranged cyanobacterial fibrils, with the hyphal sheath becoming brown and the tip of the tufts whitish. In addition, Dictyonema coppinsii is reported from Mauritius.