Key to Heterodermia (Physciaceae, Teloschistales) in Brazil, with 15 new species

The species of Heterodermia in Brazil have been revised based on literature reports, public databases and examination of 500 recent specimens from 15 states. So far, 43 species have been reported in the literature, two of which are not accepted here. We report 10 additional species from Brazil and describe 15 new to science, mostly from the Atlantic rainforest biome, raising the total number to 68, including two still undescribed species from Santa Catarina State. A key to all accepted species is given, keying out more species than represented in any previously published key of the genus. Based on new phylogenetic work, we do not accept the split genera that were recently proposed. We do informally recognize an additional group, the H. dactyliza-group. The following species are described as new: Heterodermia amphilacinulata M. F. N. Martins & M. P. Marcelli, H. caneziae M. F. Souza & Aptroot, H. delicatula M. P. Marcelli & M. F. N. Martins, H. dissecticodiademata M. F. Souza & Aptroot, H. dissecticoflabellata M. F. Souza & Aptroot, H. flavodactyliza M. F. Souza & Aptroot, H. flavulifera M. F. Souza & Aptroot, H. labiata M. P. Marcelli & M. F. N. Martins, H. macrosoraliata M. P. Marcelli & M. F. N. Martins, H. minor M. F. Souza & Aptroot, H. neocrocea M. F. Souza & Aptroot, H. nigromarginata M. F. Souza & Aptroot, H. phyllalbicans M. F. Souza & Aptroot, H. spielmannii M. F. Souza & Aptroot and H. sublinearis M. P. Marcelli & M. F. N. Martins. The following new combinations are also proposed: Heterodermia africana (Kurok.) M. F. Souza & Aptroot and H. borphyllidiata (Kalb & Meesim) M. F. Souza & Aptroot. Dissectic acid was found in species belonging to three different groups and was not restricted to (and characteristic of) one subgroup, as previously reported.