Taxonomy of the Sphaerostilbella broomeana-group (Hypocreales, Ascomycota)
Three new species, closely related to Sphaerostilbella broomeana, are described from the USA and India. These species form septate conidia from simple conidiophores with individual branches terminating in a single phialide and chlamydospores. Teleomorphs, known for S. broomeana and S. appalachiensis, are characterised by hairy perithecia and fusiform, apiculate, and conspicuously warted ascospores. This combination of characters distinguishes the S. broomeana-group from other members of Sphaerostilbella that all form gliocladium-type anamorphs and mostly grow on basidiomata of Stereum spp. Like in other species of the genus, the majority of hosts of the species described in this paper belong to wood-inhabiting taxa of Russulales. Sphaerostilbella broomeana had been recorded from a few regions in Europe and exclusively on Heterobasidion annosum. Herein, it is reported also from H. parviporum in many other localities and on H. insulare s.l. at the foothills of the Himalayas. Its sister species, found in the same region in northern India on another member of Russulales (Dichostereum effuscatum), is described as S. himalayensis. The two species described from North America colonize polypores from various taxa. Whereas S. appalachiensis occurs in eastern USA, with H. irregulare among its hosts, S. toxica is so far known only from two locations in eastern Texas, growing on Gloeophyllum striatum (Polyporales). Despite their great similarity in morphology and ITS rDNA, TEF1 sequences clearly distinguish these two North-American species. Moreover, the two strains of S. toxica appeared metabolically distinct as their organic extracts strongly inhibited the growth of human pathogenic microbes grown in vitro. Phylogenetic analysis of rDNA sequences supports monophyly of the genus Sphaerostilbella and the included S. broomeana-group, established here.
KeywordsAnamorphic fungi Antagonism Fungicolous fungi Host specialisation Hypocreaceae Parasites New taxa
KP and GB are grateful to the late Walter Gams for all his help and guidance in the world of conidial fungi, for sending and commenting on many isolates, and assistance with editing manuscripts. Thanks are also due to Jacques Fournier, Leif Ryvarden, and Oleksandr Akulov for providing specimens for this study and to Vjacheslav Spirin, who checked or provided identifications and discussion on the characters of the hosts. We are grateful to Irma Zettur and Rasmus Puusepp (University of Tartu) for the assistance in the fungal culture and molecular lab, respectively. Two reviewers and the section editor, in particular, are acknowledged for revising the manuscript.
The study was supported by the Estonian Science Agency (project IUT20-30) and the European Regional Development Fund (Centre of Excellence EcolChange). GB has been supported by University of Texas Health Science Center at Houston new faculty start-up funds, the Kay and Ben Fortson Endowment, and a grant from the NIH (R01GM121458).
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