Studies in Fungi 5(1): 125–309 (2020) www.studiesinfungi.org ISSN 2465-4973 Article Doi 10.5943/sif/5/1/12 Genera of corticioid fungi: keys, nomenclature and taxonomy Gorjón SP BIOCONS – Department of Botany and Plant Physiology, University of Salamanca, 37007 Salamanca, Spain Gorjón SP 2020 – Genera of corticioid fungi: keys, nomenclature, and taxonomy. Studies in Fungi 5(1), 125–309, Doi 10.5943/sif/5/1/12 Abstract A review of the worldwide corticioid homobasidiomycetes genera is presented. A total of 620 genera are considered with comments on their taxonomy and nomenclature. Of them, about 420 are accepted and keyed out, described in detail with remarks on their taxonomy and systematics. Key words – Corticiaceae – Crust fungi – Diversity – Homobasidiomycetes Introduction Corticioid fungi are a diverse and heterogeneous group of fungi mainly referred to basidiomycete fungi in which basidiomes are generally resupinate. Basidiome construction is often simple, and in most cases, only generative hyphae are found. In more structured basidiomes, those with a reflexed margin or with a pileate surface, more or less sclerified hyphae are usually found. Even the basidiome structure is apparently not very complex, hymenophore configuration should be highly variable finding smooth surfaces or different variations to increase the spore production area such as rugose, tuberculate, aculeate, merulioid, folded, or poroid hymenial surfaces. It is often thought that corticioid fungi produce unattractive and little variable forms and, in most cases, they go unnoticed by most mycologists as ungraceful forms that ‘cover sticks and look like a paint stain’. Although the macroscopic variability compared to other fungi is, but not always, usually limited, under the microscope they surprise with a great diversity of forms of basidia, cystidia, spores and other microscopic elements (Hjortstam et al. 1987). This diversity is reflected, even adopting an inclusive vision, as it is done here, by the number of accepted genera. Corticioid fungi are a non-natural group with species distributed in all the clades of the Basidiomycetes. They have been regarded as either a primitive group that has given rise to forms with more complicated basidiomes or as a heterogeneous assemblage of reduced forms. According to the latter hypothesis corticioid forms have evolved repeatedly through reduction from erect forms (Hibbett & Thorn 2001, Larsson et al. 2004). In recent years, several molecular studies have contributed to elucidate the relationships between different genus of corticioid fungi (Binder et al. 2005, 2010, Larsson 2007b, Larsson & Larsson 2003, Larsson et al. 2004). Hjortstam (1998) provided a very complete list of corticioid fungi and subsequent authors have continued completing it with new contributions. Here, an updated review is presented, with a traditional and pragmatic approach, of all accepted and commonly used worldwide corticioid homobasidiomycetes genera and other stipitate and pileate relatives. Comments are provided on the validity and usefulness of generic concepts, always having in mind that a genus is an artificial entity that can serve to us from a didactic point of view although their limits in most cases, from morphology, biology and even from a molecular perspective, can be confusing. Submitted 3 April 2020, Accepted 15 May 2020, Published 9 June 2020 Corresponding Author: Sergio Pérez Gorjón – e-mail – [email protected] 125 Materials & Methods In this review, original diagnoses and herbarium material has been used for the preparation of the keys and descriptions. Reference specimens are not cited in this revision since it is only about providing a general idea about the generic definition of corticioid fungi without conducting an in- depth study of type or reference specimens, although many specimens have been studied in most cases. Keys are dichotomous, based mainly on macro- and micromorphological characters. Some genera key out by several ways in the keys; this is normal since the generic concept is artificial and, in many cases, there are no specific and diagnostic generic features. For the accepted genera, a complete description is provided with comments on nomenclature, taxonomy, and phylogeny. Here, we are considering corticioid homobasidiomycetes, mainly non-poroid species, but resupinate to effuse-reflexed polypores are also included, as well as the closest pileate and stipitate relatives. For corticioid heterobasidiomycetes the reader is referred to other specific manuals and articles. The keys are intended to be posted on the website https://corticioids.webs.com/keys.htm, so they can be regularly updated and be rapidly accessible to the mycological community. Main key to groups of corticioid fungi and relatives 1. Basidiome pseudostipitate to stipitate and pileate ................................................................ Key A 1. Basidiome sessile and resupinate to slightly pileate ...................................................................... 2 2. Hymenophore poroid, with lacerate pores or with anastomosing ridges .............................. Key B 2. Hymenophore diverse, not typically poroid .................................................................................. 3 3. Spores hyaline to typically brown or violet in KOH, ornamented, telephoric acid present . Key C 3. Not with the above combination .................................................................................................... 4 4. Brown star-shaped asterohyphidia or setae present .............................................................. Key D 4. Asterohyphidia or setae absent ...................................................................................................... 5 5. Dichohyphae and/or binding-skeletal hyphae dextrinoid ..................................................... Key E 5. Not as above .................................................................................................................................. 6 6. Spores with a reaction in Melzer's reagent (amyloid or dextrinoid) .............................................. 7 6. Spores without a reaction in Melzer's reagent ............................................................................... 8 7. Spores amyloid ..................................................................................................................... Key F 7. Spores dextrinoid .................................................................................................................. Key G 8. Basidia mostly with (1-3)4 sterigmata (if number of sterigmata not known follow this step) ...... 9 8. Basidia mostly with more than 4 sterigmata ......................................................................... Key H 9. Spores distinctly thick-walled and smooth .................................................................................. 10 9. Spores thin-walled and/or ornamented and/or branched, lobed, triangular or tetrahedral .......... 11 10. Clamps either totally absent or scattered ............................................................................... Key I 10. Clamps present on nearly all septa (always at the basidial base) .......................................... Key J 11. Spores ornamented and/or branched, lobed or tetrahedral (easily seen in Melzer!) ............ Key K 11. Spores smooth .............................................................................................................................. 12 12. Lyocystidia present ............................................................................................................... Key L 12. Lyocystidia absent ....................................................................................................................... 13 13. Generative hyphae with simple septa or occasional clamps ........................................................ 14 13. Generative hyphae with clamps ................................................................................................... 15 14. Cystidial organs present (excepting hyphidia or dendrohyphidia) ...................................... Key M 14. Cystidial organs absent ......................................................................................................... Key N 15. Hyphal system dimitic/trimitic ............................................................................................. Key O 15. Hyphal system monomitic (or pseudodimitic) ............................................................................ 16 16. Dendrohyphidia or dendrophyses present ............................................................................ Key P 16. Dendrohyphidia or dendrophyses absent (paraphysoid hyphae may be present) ........................ 17 17. Cystidial organs present ........................................................................................................ Key Q 17. Cystidial organs absent ......................................................................................................... Key R 126 Key A: Basidiome pseudostipitate to stipitate and pileate 1. Hymenophore hydnoid .................................................................................................................. 2 1. Hymenophore smooth to rugose, merulioid or folded ................................................................... 6 2. Spores ornamented ......................................................................................................................... 3