Since Singer’s last Agaricales in Modern Taxonomy was published (1986), the
Agaricales (the mushroom-forming fungi) have been examined in detail, separating the order into at least one hundred and seventeen clades (Moncalvo et al., 2002). The most comprehensive analysis of the phylogeny of the Agaricales included five taxa from the Resupinateae, and these five taxa emerged as their own clade, /resupinatus, within the Agaricales (Moncalvo et al., 2002). Unfortunately, the area of the tree where /resupinatus fell was poorly resolved and resulted in a polytomy (an internal node of a phylogenetic tree which has more than two immediate descending branches), making it impossible to say with any level of certainty what fungi are the closest relatives of the Resupinateae (Moncalvo et al., 2002). Polytomies can result when too little phylogenetic information is used to construct the tree (too short a sequence, a radiation event from a single ancestral taxon, or a sequence that doesn’t show enough variation). However, this was the first study to demonstrate the molecular evolutionary relationship between Stigmatolemma and Resupinatus, supporting the morphological analysis performed by Singer in his works (Moncalvo et al., 2002). Since then, a single representative of the Resupinateae was used in a multi-locus DNA analysis of the Agaricales and it was placed in the Pleurotaceae with a high Bayesian posterior probability (1.0) but low maximum parsimony bootstrap support (Matheny et al., 2007).
Over the years, cyphelloid members of the Resupinateae have been classified in a wide variety of genera and families. The first of these families was the Thelephoraceae, which at one point was the family used to group all fungi with smooth, exposed spore-bearing surface and regular (aseptate) basidia (Burt, 1914). Coker (1921), Talbot (1956), and Cunningham (1963) also placed the cyphelloid members of the Resupinateae in the family Thelephoraceae. Currently this family contains only a few genera closely related to Thelephora Ehrh. ex Wild., with warty and usually brown basidiospores, all species obligately ectomycorrhizal, not saprotrophic (Kirk et al., 2008).
The systematic analysis performed by Burt of the Thelephoraceae, published in 15 volumes between 1914 and 1926, is one of the most comprehensive morphological analyses ever performed of a group of fungi. He provided many suggestions relating to taxonomy in general in his introduction to the Thelephoraceae, not the least of which being that more detailed species descriptions must be made (as opposed to the two- or three-line descriptions produced by the likes of Berkeley, 1873, and Saccardo, 1889) and that species do not simply belong to a group because of a lack of care taken on the part of taxonomists before applying a name to a collection (Burt, 1914). He also mentioned the problem of bound exsiccati, sets of collections of dried fungal specimens made by botanists who would then send them out to herbaria around the world. These exsiccati could also be requested from the author, or sold (and were an important source of income for many prominent mycologists of the time). Often, exsiccati were assembled and sent without great care being paid to ensuring that multiple collections with a given species name, distributed among the various sets, were actually the same species! This problem noted by Burt is still a problem today; far too many herbarium collections are specimens that were identified macroscopically (often without even the use of a dissecting
microscope) and bear an incorrect name.
Once some mycologists recognized that the Thelephoraceae was no longer an appropriate location for cyphelloid fungi, these fungi were all transferred to the families
Cyphellaceae Lotsy or Porotheleaceae Murrill (e.g., Pilát, 1925; Bourdot & Galzin, 1927; Cunningham, 1953; Cooke, 1957 & 1961; Donk, 1962). Many species were treated in the genera Cyphella, Solenia, or Porotheleum. Cyphella is still a genus of fungi
in the Cyphellaceae (a family in the Agaricales), but Solenia Pers. (a later homonym of Solena Lour.) is a synonym of Henningsomyces Kuntze (Kirk et al., 2008). Phylogenetic analyses of DNA sequences place Cyphella in the /Cyphellaceae clade, Henningsomyces, and Porotheleum in the hydropoid clade, both of which are nested within the larger /marasmioid clade (IV) (Moncalvo et al., 2002; Matheny et al., 2007).
Cooke (1957) emphasized the taxonomic importance of the subiculum over all other microscopic characters and transferred all of the cyphelloid fungi with a prominent subiculum to the genus Porotheleum, in the Porotheleaceae. Donk (1962) noted that there was no morphological evidence other than similar fruit body morphology to suggest that Porotheleum and any other fungus producing cyphelloid fruit bodies with a
subiculum were closely related, but he continued to use the family Cyphellaceae as a convenience for those that could not readily be connected elsewhere. Donk (1962) resurrected the genus Stigmatolemma (after a proper description of the type species, Stigmatolemma incanum Kalchbr., by Talbot, 1956), transferred the known members of the genus into it, and placed it in the Cyphellaceae.
At the same time, Singer was reorganizing the Agaricales into groups that better reflected shared morphological characters. He created the tribe Resupinateae within the
Pleurotaceae (Singer, 1948) for the genera Resupinatus and Hohenbuehelia, which both had a gelatinous zone in the flesh of the cap. Singer (1962) then added Asterotus to the Resupinateae, but later synonymized this genus with Resupinatus (Singer, 1973). Based on the the similarities in micromorphology between Resupinatus kavinii (then classified in Geopetalum) and Stigmatolemma poriaeforme (then classified in Solenia), noted by Pilát (1935, p. 66), Singer (1975a) transferred Stigmatolemma to the Resupinateae in the 3rd edition of his Agaricales in Modern Taxonomy as a “reduced series” derived from the gilled genus Resupinatus. Molecular evidence has since supported the relationship of Stigmatolemma within the Resupinateae (Thorn et al., 2005), but also shown that fungi with cyphelloid fruit bodies have evolved multiple times within the Agaricales (Hibbett & Binder, 2002; Moncalvo et al., 2002; Bodensteiner et al. 2004). Hohenbuehelia was transferred to the Pleurotaceae (and thus out of the Resupinateae) as the sister genus to Pleurotus by Thorn et al. (2000) but Matheny et al. (2007) have since argued that
Resupinatus belongs within an expanded Pleurotaceae. This argument is not addressed in this thesis.
The goal of this study is to determine the membership of the Resupinateae. Singer (1975a, 1986) placed Aphyllotus and Stromatocyphella in the Resupinateae, and this hypothesis (made based on morphology alone) has never been tested using molecular data. This study will also test the monophyly of species classified as Stigmatolemma within Resupinatus and determine if the cyphelloid habit evolved once or multiple times within the Resupinateae.