The Xylonomycetes are a

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, which holds 2

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

s of ''Symbiotaphrinales'' , and ''Xylonales'' .

History

During a culture-based survey of living

sapwood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin that ...

and leaves of rubber trees (''

Hevea ''Hevea'' is a genus of flowering plants in the spurge family, Euphorbiaceae, with about ten members. It is also one of many names used commercially for the wood of the most economically important rubber tree, '' H. brasiliensis''. The genus is ...

'' spp.) in remote forests of Peru. Multilocus phylogenetic analyses reveal that this new lineage came from the radiation of the '' Leotiomyceta'' class which generated several other classes including

Arthoniomycetes Arthoniomycetes are a class of ascomycete fungi. It includes two orders: Arthoniales and Lichenostigmatales. Most of the taxa in these orders are tropical and subtropical lichens. Systematics Phylogenetic analysis supports the monophyly of thi ...

Dothideomycetes Dothideomycetes is the largest and most diverse class of ascomycete fungi. It comprises 11 orders 90 families, 1,300 genera and over 19,000 known species. Wijayawardene et al. in 2020 added more orders to the class. Traditionally, most of it ...

Eurotiomycetes Eurotiomycetes is a large class of ascomycetes with cleistothecial ascocarps within the subphylum Pezizomycotina, currently containing around 3810 species according to the Catalogue of Life. It is the third largest lichenized class, with more th ...

Geoglossomycetes Geoglossaceae is a family of fungi in the order Geoglossales, class Geoglossomycetes. These fungi are broadly known as earth tongues. The ascocarps of most species in the family Geoglossaceae are terrestrial and are generally small, dark in col ...

Lecanoromycetes Lecanoromycetes is the largest class of lichenized fungi. It belongs to the subphylum Pezizomycotina in the phylum Ascomycota. The asci (spore-bearing cells) of the Lecanoromycetes most often release spores by rostrate dehiscence. The group is ...

Leotiomycetes The Leotiomycetes are a class of ascomycete fungi. Many of them cause serious plant diseases. Systematics The class Leotiomycetes contains numerous species with an anamorph placed within the '' fungi imperfecti'' (deuteromycota), that have onl ...

Lichinomycetes Lichinales is the sole order (biology), order of ascomycete fungi in the class Lichinomycetes. It contains three family (biology), families: Gloeoheppiaceae (3 genus, genera), Lichinaceae (43 genera), and Peltulaceae (1 genus). Most species are l ...

and

Sordariomycetes Sordariomycetes is a class of fungi in the subdivision Pezizomycotina (Ascomycota). It is the second-largest class of Ascomycota, with a worldwide distribution that mostly accommodates terrestrial based taxa, although several can also be found in ...

. Due to the unique morphological, physiological, and ecological traits relative to known

endophytes An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; ...

, ''Xylonomycetes'' was deemed unique enough to be separate. Within the superclass of

Pezizomycotina Pezizomycotina is the largest subdivision of Ascomycota, containing the filamentous ascomycetes and most lichenized fungi. It is more or less synonymous with the older taxon Euascomycota. These fungi reproduce by fission rather than budding. Thi ...

, the 6 classes (including Pezizomycetes and Orbiliomycetes) were

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

apart from Xylonomycetes. Xylonomycetes, Eurotiomycetes and Dothideomycetes were deemed to have had a single origin. They contain unspecific peroxygenases (UPO)

enzymes An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as pro ...

which can be used to determine taxonomic afflication. It contains the wood endophytes in ''Xylona'' and the endosymbionts of beetles in ''Symbiotaphrina''. It has been suggested that these seeming unrelated genera might be linked via a

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

-like stage. As an asexual yeast living within the insect guts, with an asexual mycelial form and then a sexual form associated with the dead wood. Although, the frequency of transfer between free-living and symbiotic conditions is unknown and could be very low. As the yeasts are transferred vertically via the

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...

of the female inset to the egg surface.Angela E. Douglas

Taxon

Xylonomycetes holds (orders and families); * Symbiotaphrinales ** Symbiotaphrinaceae , 2018 * Xylonales ** Xylonaceae , 2012

References

{{Taxonbar, from=Q26896793 Ascomycota Fungal plant pathogens and diseases Fungus classes