''Sistotrema'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 ...

in the family Hydnaceae. The genus contains at least 55 species and has a worldwide distribution. The type species is ''Sistotrema confluens'' Pers. (1794).

Ecology

The genus includes both terricolous and lignicolous species. Most species of ''Sistotrema'' are white rotting saprotrophs which often occur on highly decayed wood and on bark of attached, dead branches, but endophytic and

ectomycorrhizal An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobion ...

nutritional modes also exist in some species. ''Sistotrema confluens'' is

ectomycorrhiza An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobio ...

l and ''S. alboluteum'', ''S. muscicola'' and ''S. albopallescens'' are suspected of being so. In the genus only ''S. confluens'' and ''S. subconfluens'' are known to grow on soil. Basidiocarps of ''Sistotrema'' generally start spore production very early.

Morphology

Only the type species ''S. confluens'', and ''S. subconfluens'', form stipitate

basidiocarps In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do no ...

while all other species in the genus form resupinate, corticioid basidiocarps. There is large variation in the configuration of the

hymenophore A hymenophore refers to the hymenium-bearing structure of a fungal fruiting body. Hymenophores can be smooth surfaces, lamellae, folds, tubes, or teeth. The term was coined by Robert Hooke Robert Hooke (; 18 July 16353 March 1703) was an ...

, which can range from strictly hydnoid to poroid, but the dominating type of hymenophore is smooth. Basidiocarps are soft and membranaceous or ceraceous, and can be pelliculose or waxy. The hyphal system is monomitic and consist of generative hyphae with clamps, which are often ampullate. The subicular hyphae have characteristically oily contents and the septa have perforate parenthesomes.

Basidia A basidium (: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies are also ...

are urniform and usually have 6-8

sterigmata In biology, a sterigma (: sterigmata) is a small supporting structure. It commonly refers to an extension of the basidium (the spore-bearing cells) consisting of a basal filamentous part and a slender projection which carries a spore at the tip ...

, but some species are known to mainly have 2-4 sterigmata.

Basidiospore A basidiospore is a reproductive spore produced by basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid Ploidy () is the number of complete sets of chromos ...

s are small, smooth, hyaline and ranging between globose, ellipsoid, oblong or allantoid in shape. They are thin-walled and non-cyanophilous, non-amyloid and non-dextrinoid.

Cystidia A cystidium (: cystidia) is a relatively large cell found on the sporocarp of a basidiomycete (for example, on the surface of a mushroom gill), often between clusters of basidia. Since cystidia have highly varied and distinct shapes that are o ...

are mostly absent but some species have enclosed gloeocystidia or projecting leptocystidia.

Phylogenetics

''Sistotrema'' has been considered a well delimited genus by the urniform basidia, the number of sterigmata and the oily contents of the hyphae.

Phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses during the 21st century have, however, shown that ''Sistotrema'' is a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

genus. It is closely related to the genera ''

Hydnum ''Hydnum'' is a genus of fungi in the family Hydnaceae. They are notable for their unusual spore-bearing structures of teeth rather than Lamella (mycology), gills. The best known are the Edible mushroom, edible species ''Hydnum repandum'' and ''H ...

'', '' Clavulina'', and '' Membranomyces.'' The mycorrhizal species of ''Sistotrema'' form a monophyletic group with the mycorrhizal genus ''Hydnum'', while the remaining saprophytic species in the genus have been suggested by Larsson (2007) to be distributed over several other genera. Species of ''Sistotrema'' have stichic basidia which means that the spindle has a longitudinal orientation during meiosis. This character is unique to the Cantharellales, while all other

Agaricomycetes The Agaricomycetes are a class of fungi in the division Basidiomycota. The taxon is roughly identical to that defined for the Homobasidiomycetes (alternatively called holobasidiomycetes) by Hibbett & Thorn, with the inclusion of Auriculariales ...

have chiastic basidia with a transversely oriented spindle. Eriksson et al. (1984) mentions that ''S. heteronemum'' differs the most from other species in the genus and that its placement in ''Sistotrema'' is not certain. It differs from other species in having cyanophilous hyphal walls and basal hyphae which are partly pigmented brown, which according to the authors shows affinity with '' Botryobasidium''.

Taxonomy

The genus was originally designated to a single species by

Fries French fries, or simply fries, also known as chips, and finger chips (Indian English), are ''List of culinary knife cuts#Batonnet, batonnet'' or ''Julienning, julienne''-cut deep frying, deep-fried potatoes of disputed origin. They are prepa ...

, but microscopical studies has since added many more species to ''Sistotrema''.

Species

References

{{Taxonbar, from=Q4120102 Cantharellales Agaricomycetes genera