Arthromyces and Blastosporella, two new genera of conidia-producing lyophylloid agarics (Agaricales, Basidiomycota) from the neotropics
Introduction
Three new conidial forming agaric species have been found in neotropical montane forests of Puerto Rico, Dominican Republic, Colombia, and Belize. Two of these species form dark-pigmented and ornamented arthrospores with schizolytic secession (Walther et al. 2005), whereas the other taxon produces dark-pigmented and ornamented blastospores. These three new species share several morphological characters that might indicate they belong in the same genus, i.e. dark brown, powdery conidia production on the pileus and stipes, thin-fleshed, glabrous pileus, very crowded and narrow lamellae that produce white spore deposits, abundant and well-formed, narrow cheilocystidia, small, hyaline, pip-shaped or ellipsoid, smooth inamyloid basidiospores that have cyanophilic walls, narrow, equal and rather tough stipes, and basidia with siderophilous/cyanophilous bodies (granules). The differences in conidial formation suggest distinct lineages, and an analysis of the nuLSU rDNA region (Hofstetter, unpublished data) show that the arthrosporic forming taxa are clearly distinct from the blastospore-forming taxon. The arthrospore-forming taxa appear to be related to Termitomyces, whereas the blastospore-forming species is separate from this group and allied with Tephrocybe rancida. These relationships based on an analysis of a broader molecular dataset will be dealt with in a separate paper.
We also compared the ITS sequences of the asexual spores to ITS sequences from tissue extracts of the basidiomata to confirm that the asexual stages were in fact being produced by the basidiomata. Several samples were run for each species and all ITS sequences confirmed that the conidial states were indeed being produced by the basidiomata. Attempts to germinate the conidia of Arthromyces claviformis were not successful.
We originally thought these new taxa might be members of the genus Arthrosporella because they formed dry powdery conidia directly on the basidiomata. Arthrosporella was described as monotypic by Singer (1970) for a single collection he made with Digilio in Anta Muerta, Tucumán, Argentina in April 1949. The type collection was found in the ‘subtropical forests of the Myrtaceae (fog-) zone at 1000–1100 m alt.’ Singer (1950) originally considered this taxon as a species of Armillariella, and 20 y later realized this organism was not morphologically related to the other species in Armillariella (syn. Armillaria). The collection was unusual for a member of the Agaricales, as it consisted of independent teleomorph and anamorph states. The agaricoid form he called Arthrosporella ditopa and the clavarioid, but totally anamorphic form, he described as Nothoclavulina ditopa (Singer 1970). The unusual feature about this species was that the agaricoid basidiomata produced white, colourless, smooth arthrospores on the pileus and stipe that were identical to the white, colourless, smooth arthrospores produced on the clavarioid counterpart it was found fruiting with. Arthromyces and Blastosporella produce very different kinds of conidia as compared with Arthrosporella and a phylogenetic connection between Arthrosporella and these two new genera now seems dubious after studying what remains of the type collection of Arthrosporella. The only material left in the type collection of A. ditopa is an arthrospore covered clavarioid fruiting structure. The arthrospores on that structure are hyaline, thin-walled, globose, smooth, and often with a ‘clamp-like’ structure at the juncture between conidia. The specimen is not suitable for DNA extraction and we did not have permission to do so in any case. The agaricoid part of the collection no longer exists, and unfortunately, Arthrosporella ditopa is known only from the type collection.
Many agarics produce anamorphic states at least in culture (Watling, 1979, Kendrick and Watling, 1979, Walther et al., 2005), but significantly fewer produce those anamorphs directly on the teleomorphic basidiomata. Cystoderma jasonis (syn Cystoderma amianthinum var. longisporum), C. tricholomoides, Asterophora parasitica, A. lycoperdoides, Dendrocollybia racemosa, Pleurotus cystidiosus, Squamanita odorata, S. paradoxa, and S. pearsonii are the other species, besides Arthrosporella ditopa, that produce some form of conidia directly on the already-formed agaricoid basidiomata (Bas, 1965, Harmaja, 1979, Heinemann and Thoen, 1973, Kendrick and Watling, 1979, Kühner, 1969). The acanthocysts on the surfaces of fruiting bodies of Mycena section Saccharifereae are able to germinate and grow, thus apparently playing a role in asexual reproduction (Desjardin 1995) and therefore might well qualify to be considered members in this small group of fungi that produce anamorphic states directly on the basidium-forming teleomorph. Arthromyces and Blastosporella can also now be added to this small group of agarics known to have anamorphs directly associated with the teleomorph.
Arthromyces and Blastosporella appear to be solely New World taxa, and more specifically, tropical taxa restricted to montane or even cloud forest environments. At least one species, described from Malesia by Corner (1994), Tricholoma furcatifolium, may eventually be shown to have some affinities with Arthromyces because of its very similar morphological appearance to A. claviformis. However, as described by Corner (1994), T. furcatifolium does not produce an anamorphic state, nor does it have siderophilous basidia. Other taxa in the Malesian mycota that might also be compared with Arthromyces because of similar macromorphology are T. umbraticum and Collybia umbraticoides. Corner (1994) indicated these two taxa may have some affinities with each other and to T. furcatifolium. The resemblances may only be superficial but the similarities are striking enough to warrant future investigations.
Blastosporella is known only from Colombia and the Dominican Republic. One of the species of Arthromyces has been found in Puerto Rico and The Dominican Republic, whereas a completely different species of Arthromyces is only known from the highest peak in Belize.
Section snippets
Materials and methods
Colour notations in the macroscopic descriptions are from Kornerup & Wanscher (1978). Methods used in preparation of microscopic structures were those of Baroni (1981). Testing for cyanophilic reactions of spore walls and other structures was carried out as follows: un-revived lamella fragments were gently heated over a flame in a drop of Cotton blue/lactic acid (Singer 1986) on a clean glass slide; when the mountant began to release vapour (not boiled), the fragment was removed and placed in a
Taxonomy
Arthromyces T. J. Baroni & Lodge, gen. nov.
MycoBank no.: MB510711
Habitus mycenoideus vel collybioideus, lamellis affixis percongestis angustissimis, superficie pilei stipitisque catenulas ex arthroconidiis obscure fusco-brunneis vel obscure olivaceo-brunneis compositas formante, basidia corpora siderophilica vel cyanophilica habentia, parietibus basidiosporicis cyanophilicis.
Species with a mycenoid or collybioid habit with extremely crowded and very narrow, attached lamellae, surface of pileus
Acknowledgements
Fieldwork was made possible for T. J. B., D. J. L., D. L. L. and E. H. by a grant from the National Science Foundation, Biodiversity Surveys and Inventories Program to the State University of New York, College at Cortland (DEB-9525902 and DEB-0103621). We are especially grateful to Andrés Ferrer formerly of the Fundación Moscoso Puello and now the director of the Nature Conservancy in the Caribbean for advice and logistical support in the Dominican Republic. We also thank our other Dominican
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Ancestral predisposition toward a domesticated lifestyle in the termite-cultivated fungus Termitomyces
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