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Insights into Claussenomyces Kirschst.: Past, Present and Future

The Leotiomycetes are recognized as one of the most diverse classes of Ascomycota. Despite the high diversity in this class, certain orders and families have a high proportion of taxa that have not been studied using molecular methods. A good example of the paucity of molecular data is found in Tympanidaceae (Baral 2015), a poorly studied family containing nine genera, which have previously been placed in the Bulgariaceae, Dermateaceae, and Helotiaceae: Claussenomyces, Collophora, Durandiella, Grovesiella, Holwaya, Micraspis, Myriodiscus, Pragmopora, and Tympanis. Some of them are associated with diseases such as bark and xylem lesions, internal necrosis, vascular streaking, cankers and crown damage (Quijada 2015, Baral 2016). The genus Claussenomyces was erected by Kirschstein in 1923 for a single species (C. jahnianus). Korf and Abawi (1971) drastically widened the concept of the genus combining and adding three species: Holwaya salicis E. Müll. and S. Ahmad, Corynella prasinula (P. Karst.) Boud., and Corynella atrovirens (Pers.) Boud. Currently, Claussenomyces is one of the most diverse genera in Tympanidaceae with 16, mostly conifer-associated species, with corticolous, lignicolous, fungicolous, and resinicolous lifestyles. A monographic treatment of the genus does not exist, and only a few species — C. kirschsteinianus, C. prasinulus, C. olivaceus, C. cf. hydnicola, Claussenomyces sp. or uncultured Claussenomyces — have publicly available sequences (NCBI). Baral and Marson (2005) provided for first time a key to species of the genus, but also a revision of several species and types (C. jahnianus, C. pusillus, Tympanis xylophila). In 2013, the first author started to work in the genus and reviewed more than 40 collections, including most of the types with the exception of C. kirschsteinianus, C. simplex and C. pleomorphicus. Another additional 15 collections have been treated in detail jointly by the second and third author previous to the present work. Current results of our morphological and phylogenetic analyses revealed that Claussenomyces is a polyphyletic genus that should be split into at least four genera represented as: C. jahnianus, C. atrovirens group, C. prasinulus group, and C. kirschsteinianus group. The three former are related to Phacidiales whereas the latter is related to Helotiales. Although C. jahnianus still lacks molecular data, we consider it different from all remaining species based on its deviating morphology, but tentatively place it in the Phacidiales. In addition, several species currently included in Claussenomyces belong to other genera (i.e. Claussenomyces pini in Durandiella, C. tympanoides = C. pusillus in Holwaya), or are synonyms of other species in the Claussenomyces (i.e. C. canariensis and C. clavatus being conspecific with C. atrovirens). In the future, the 16 current binominals will be reduced to 10 species, divided into four genera: Claussenomyces, restricted to its type species (C. jahnianus), and three newly erected genera defined by phylogenic, microscopic, and ontogenetic features as follows: (1) fungicolous, lignicolous and resinicolous species with true ascoconidia (C. atrovirens group, 6 species) ; (2) lignicolous species without ascoconidia (C. prasinulus, 1 species) and (3) resinicolous species without ascoconidia (C. kirschsteinianus group, 2 species).

fungi ; phylogeny ; taxonomy ; Tympanidaceae

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