A first assessment of Galapagos basidiolichens

Abstract

As part of an ongoing comprehensive inventory of Galapagos lichens, a first assessment of the morphology and anatomy of basidiolichens from the archipelago is presented here. It is the basis for further studies of the taxonomy, ecology and biogeography of this poorly known group of lichens. Four genera, all in Hygrophoraceae, can be distinguished: Acantholichen, Cora, Cyphellostereum and Dictyonema. Both Acantholichen and Cora are characterized by chroococcoid cyanobionts and a heteromerous thallus with a distinct upper cortex and photobiont layer. The monotypic Acantholichen pannarioides is entirely composed of small, branched, inflated squamules that appear densely pruinose because their cortical hyphae bear characteristically swollen, densely spinose end cells (acanthohyphidia); this species has never been observed fertile. The common Cora glabrata is foliose, forming large, radially zonate, conch-like, often tiled thalli, when fertile with circular lines of basidiocarps on its lower side. Dictyonema is distinguished by filamentous cyanobionts and distinctly filamentous thalli that are homomereous (i.e., not distinctly layered); all species of Dictyonema s.str. have trichomes (filamentose cyanobacterial photobionts) closely enveloped by fungal cells of a jigsaw pattern. In D. sericeum thallus filaments (i.e., individual fibrils) aggregate to form shelf-like structures similar in appearance to polyporoid bracket fungi; basidiocarps develop in irregular patches on the lower side of these shelves. In contrast, fibrils of D. schenkianum grow encrusting their substrate with irregularly to suberect trichomes, occasionally bearing basidiocarps dispersed across the thallus. Two other species in Galapagos show adpressed growth form and are described here as new: Dictyonema pectinatum, which is characterized by large parallel fibrils with paler, papillate tips, and D. galapagoense, characterized by thin trichomes of more squarrish elongate cells. The genus Cyphellostereum is represented by two species: the newly described C. imperfectum and an unnamed Cyphellostereum sp., both phenotypically similar to free-living cyanobacterial filaments. Cyphellostereum imperfectum has narrow photobiont filaments with irregular hyphal sheath leaving interspaces; macroscopically it shows a bluish green thallus with a distinct prothallus. Cyphellostereum sp. has a rather uncommon basidiolichen appearance: thin sctytonematoid fibrils surrounded by straight fungal cells forming shiny tufts. The new combination Cyphellostereum nitidum is also proposed. The ecology and taxonomy of Galapagos basidiolichens is briefly discussed and a key and short descriptions of all species are presented.

Ten new species of lichenized Basidiomycota in the genera Dictyonema and Cora (Agaricales: Hygrophoraceae), with a key to all accepted genera and species in the Dictyonema clade

“…(Berkeley 1843: 639) (see Mitidieri et al 1964;Feige 1969;Oberwinkler 1970Oberwinkler , 1984Oberwinkler , 2001Parmasto 1978;Coxson 1987a-c;Fritz-Sheridan & Portecop 1987;Iacomini et al 1987;Fritz-Sheridan 1988;Larcher & Vareschi 1988;Wolf 1993;Lange et al 1994;Piovano et al 1995;Thomas et al 1997;Azenha et al 1998;Trembley et al 2002a, b;Carbonero et al 2002;Elifio et al 2002). Taxonomic and phylogenetic studies, however, suggest that both names comprise a fairly large number of species, many undescribed (Chaves et al 2004;Lücking 2008;Lawrey et al 2009;Yánez et al 2012;Dal-Forno et al 2013). This also has implications on the correct use of the epithets glabratum and pavonia for foliose forms, for which Hawksworth (1988) pointed out that, in case of synonymy, glabratum would be the correct usage, being sanctioned through its adoption by Fries (1821).…”

“…can be divided into five genera, Cyphellostereum D. A. Reid (Reid 1965: 336), Dictyonema s.str., Acantholichen P. M. Jørg. (Jørgensen 1998: 444), Cora, and Corella (Lawrey et al 2009;Dal-Forno et al 2013), and this concept was applied to a treatment of Galápagos basidiolichens (Yánez et al 2012). These genera are well-distinguished morphologically and anatomically (Oberwinkler 1984(Oberwinkler , 2012: Cyphellostereum and Dictyonema have filamentous thalli with the mycobiont forming a hyphal sheath around the cyanobacterial filaments, the sheath consisting of irregular hyphae (lacking haustoria) in Cyphellostereum and of jigsaw-puzzle-shaped cells (forming haustoria) in Dictyonema s.str.…”

A single macrolichen constitutes hundreds of unrecognized species

“…Subsequent taxonomic and molecular phylogenetic studies suggested that this concept did not reflect the true diversity in this clade (7,12,13). Currently, a total of 43 species are recognized in five genera (14,15). Two genera, Cora and Corella, are foliose macrolichens, with a total of 16 species, corresponding to what was considered a single species, Dictyonema glabratum (11,12,16).…”

New species ofDictyonemaandCyphellostereum(lichenizedBasidiomycota:Hygrophoraceae) from tropical Africa and the Indian Ocean, dedicated to the late Hildur Krog

“…Hence, the phylogenetic placement of the new species must be tested with molecular sequence data. Morphologically, it is most similar to C. imperfectum, which differs in the distinct white hypothallus (not associated with hymenophores) and the denser hyphal sheath around the cyanobacterial filaments (Yánez & al. 2012).…”

“…2014a). Dictyonema galapagoense also forms (sub-)erect tufts of fibrils but is much more delicate and lacks fungal haustoria, so the photobiont filaments are much narrower, with more or less squared cells (Yánez & al. 2012).…”