• Kingdom Fungi

  Eukaryotic (with true nuclei); acellular (e.g., highly adapted parasites), unicellular (e.g., species adapted to life in small volumes of fluid), or multicellular (filamentous) with hyphae; cell walls composed of chitin, polysaccharides (e.g., glucans), or both; can be individually microscopic in size (i.e., yeasts); at least 99,000 species of fungi have been described.

  • Phylum Chytridiomycota

    Mainly aquatic, some are parasitic or saprotrophic; unicellular or filamentous; chitin and glucan cell wall; primarily asexual reproduction by motile spores (zoospores); mycelia; contains 2 classes.

    • Class Chytridiomycetes

      Aquatic parasitic (on algae, fungi, or flowering plants) or saprotrophic; unicellular or filamentous; motile cells characterized by a single posterior flagellum; monocentric thallus or polycentric rhizomycelial; contains 3 orders.

      • Order Chytridiales

        Mainly found in soil; examples of genera include Chytridium, Chytriomyces, and Nowakowskiella.

      • Order Rhizophydiales

        Aquatic parasitic (on algae) or saprotrophic (in soil or on pollen, keratin, or chitin); sporangia spherical or angular; rhizoids branched; example genus is Rhizophydium.

      • Order Spizellomycetales

        Parasitic on soil organisms and plants; holocarpic (having all the thallus involved in the formation of the fruiting body) or eucarpic; example genera include Spizellomyces and Powellomyces.

    • Class Monoblepharidomycetes

      Asexual reproduction by zoospores or autospores; filamentous, branched or unbranched thallus; contains 1 order.

      • Order Monoblepharidales

        Sexual reproduction by motile gamete (antherozoid) fertilizing nonmotile differentiated egg, resulting in thick-walled oospore; example genus is Monoblepharis.

  • Phylum Neocallimastigomycota

    Found in digestive tracts of herbivores; anaerobic; zoospores with one or more posterior flagella; lacks mitochondria but contains hydrogenosomes (hydrogen-producing, membrane-bound organelles that generate energy in the form of adenosine triphosphate, or ATP); contains 1 class.

    • Class Neocallimastigomycetes

      Contains 1 order.

      • Order Neocallimastigales

        Digest cellulose; example genus is Neocallimastix.

  • Phylum Blastocladiomycota

    Parasitic on plants and animals, some are saprotrophic; aquatic and terrestrial; flagellated; alternates between haploid and diploid generations (zygotic meiosis); contains 1 class.

    • Class Blastocladiomycetes

      Parasitic or saprotrophic; contains 1 order.

      • Order Blastocladiales

        Parasitic (on many different substrates, including decaying fruits) or saprotrophic; example genera include Allomyces and Coelomomyces.

  • Phylum Microsporidia

    Parasitic on animals and protists; unicellular; highly reduced mitochondria; phylum not subdivided due to lack of well-defined phylogenetic relationships within the group.

  • Phylum Glomeromycota

    Forms obligate, mutualistic, symbiotic relationships in which hyphae penetrate into the cells of roots of plants and trees (arbuscular mycorrhizal associations); coenocytic hyphae; reproduces asexually; cell walls composed primarily of chitin.

    • Class Archaeosporomycetes

      Arbuscular mycorrhizal; spores form singly or in loose clusters.

      • Order Archaeosporales

        Arbuscular mycorrhizal; example genera include Archaeospora and Geosiphon.

    • Class Glomeromycetes

      Arbuscular mycorrhizal; single or clustered spores; contains 4 orders.

      • Order Diversisporales

        Arbuscular mycorrhizal; forms complexes of spores; example genera include Acaulospora, Diversispora, and Pacispora.

      • Order Gigasporales

        Arbuscular mycorrhizal; uses extra-radical auxiliary cells instead of vesicles in plant roots.

      • Order Glomerales

        Arbuscular mycorrhizal; forms single spores, loose clusters of spores, or compact sporocarps (fruiting bodies); example genus is Glomus.

    • Class Paraglomeromycetes

      Arbuscular mycorrhizal; forms complexes of spores.

      • Order Paraglomerales

        Arbuscular mycorrhizal; example genus is Paraglomus.

  • Subphylum Mucoromycotina (incertae sedis; not assigned to any phylum)

    Parasitic, saprotrophic, or ectomycorrhizal (forms mutual symbiotic associations with plants); asexual or sexual reproduction; branched mycelium; contains 3 orders that represent the traditional Zygomycota.

    • Order Mucorales (pin molds)

      Parasitic or saprotrophic; filamentous; nonmotile spores (aplanospores); coenocytic mycelium; asexual reproduction by formation of sporangiospores; example genera include Mucor, Parasitella, Phycomyces, Pilobolus, and Rhizopus.

    • Order Endogonales

      Saprotrophic or mycorrhizal; filamentous; coenocytic mycelium; underground sporocarp; example genera include Endogone, Peridiospora, Sclerogone, and Youngiomyces.

    • Order Mortierellales

      Parasitic or saprotrophic; fine mycelium, branched (arachnoid); sporangia with 1 or many spores; may form chlamydospores (thick-walled asexual spores); produces garliclike odour; example genera include Mortierella, Dissophora, and Modicella.

  • Subphylum Entomophthoromycotina (incertae sedis)

    Pathogenic, saprotrophic, or parasitic; coenocytic or septate mycelium; rhizoids formed by some species; conidiophore branched or unbranched; conidia forcibly discharged; contains 1 order.

    • Order Entomophthorales

      Primarily parasitic on insects, some may be saprotrophic in soil; coenocytic mycelium, may become septate; example genera include Entomophthora, Ballocephala, Conidiobolus, Entomophaga, and Neozygites.

  • Subphylum Zoopagomycotina (incertae sedis)

    Endoparasitic (lives in the body) or ectoparasitic (lives on the body) on nematodes, protozoa, and fungi; thallus branched or unbranched; asexual and sexual reproduction; contains 1 order.

    • Order Zoopagales

      Parasitic on amoebas, rotifers, nematodes, and other protozoa; asexual reproduction by conidia borne singly or in chains, not forcibly discharged; example genera include Cochlonema, Rhopalomyces, Piptocephalis, Sigmoideomyces, Syncephalis, and Zoopage.

  • Subphylum Kickxellomycotina (incertae sedis)

    Saprotrophic, may be parasitic on fungi, can form symbiotic associations; thallus forms from holdfast on other fungi; mycelium branched or unbranched; asexual and sexual reproduction; contains four orders.

    • Order Kickxellales

      Primarily saprotrophic; mycelium highly branched and occasionally coenocytic; example genera include Kickxella, Coemansia, Linderina, and Spirodactylon.

    • Order Dimargaritales

      Mycoparasitic; example genera include Dimargaris, Dispira, and Tieghemiomyces.

    • Order Harpellales

      Endosymbiotic, found in the digestive tracts of insects, including mayflies and stoneflies; thallus simple or branched, septate; asexual reproduction by trichospores; sexual reproduction zygomycetous; example genera include Harpella, Furculomyces, Legeriomyces, and Smittium.

    • Order Asellariales

      Endosymbiotic, found in the digestive tracts of arthropods; thallus branched, septate, attached by basal coenocytic cell; asexual reproduction by arthrospores; example genera include Asellaria and Orchesellaria.

  • Phylum Ascomycota (sac fungi)

    Symbiotic with algae to form lichens, some are parasitic or saprotrophic on plants, animals, or humans; some are unicellular, but most are filamentous; hyphae septate with 1, rarely more, perforation in the septa; cells uninucleate or multinucleate; asexual reproduction by fission, budding, or fragmentation or by conidia that are usually produced on sporiferous (spore-producing) hyphae, the conidiophores, which are borne loosely on somatic (main-body) hyphae or variously assembled in asexual fruiting bodies; sexual reproduction by various means resulting in the production of meiosphores (ascospores) formed by free-cell formation in saclike structures (asci), which are produced naked or, more typically, are assembled in characteristic open or closed bodies (ascocarps, also called ascomata); ascomycota include some cup fungi, saddle fungi, and truffles; this phylum is sometimes included in the subkingdom Dikarya with its sister group, Basidiomycota.

    • Subphylum Taphrinomycotina

      Pathogenic on some plants; unicellular or filamentous; asci produced on the plant surface; ascocarp absent; contains 4 classes.

      • Class Taphrinomycetes

        Parasitic or pathogenic on plants; naked asci; contains 1 order.

        • Order Taphrinales

          Parasitic on plants, causing gall formation; naked asci; example genera include Taphrina and Protomyces.

      • Class Neolectomycetes

        Parasitic or pathogenic on plants; some with large ascocarps; contains 1 order.

        • Order Neolectales

          Parasitic on plant roots; produces large ascocarps; forms yeastlike conidia; example genus is Neolecta.

      • Class Pneumocystidomycetes

        Parasitic or pathogenic in animals; contains 1 order.

        • Order Pneumocystidales

          Parasitic in the alveoli of the lungs of some vertebrates; asexual reproduction by fission; example genus is Pneumocystis.

      • Class Schizosaccharomycetes

        Primarily saprotrophic; groups of fused ascospores may be present; contains 1 order.

        • Order Schizosaccharomycetales (fission yeasts)

          Saprotrophic in fruit juice; asexual reproduction by fission; asci fuse to form groups of 4 or 8 ascospores; example genus is Schizosaccharomyces.

    • Subphylum Saccharomycotina (true yeasts)

      Saprotrophic on plants and animals, including humans, occasionally pathogenic in plants and humans; unicellular; found in short chains; asexual reproduction by budding or fission; contains common yeasts that are relevant to industry (e.g., baking and brewing) and that cause common infections in humans; contains 1 class.

      • Class Saccharomycetes

        Saprotrophic or pathogenic; yeasts reproduce by budding or fission; contains 1 order.

        • Order Saccharomycetales (ascomycete yeasts)

          Saprotrophic or pathogenic in plants and humans; cell walls lack chitin; asci form singly or in chains; example genera include Saccharomyces, Candida, Dipodascopsis, and Metschnikowia.

    • Subphylum Pezizomycotina

      Symbiotic with algae to form lichen; contains all ascomycetes able to produce ascomata; many form ascocarps, although some have lost the ability to undergo meiosis and cannot produce asci (formerly Deuteromycota); contains 10 classes.

      • Class Arthoniomycetes

        Forms lichens; contains 1 order.

        • Order Arthoniales

          Forms lichens; produces asci that elongate to discharge spores; example genera include Arthonia, Dirina, and Roccella.

      • Class Dothideomycetes

        Pathogenic, endophytic, or epiphytic on plants, saprotrophic in soil, parasitic on fungi and animals, or symbiotic with algae to form lichens; spores undergo ascolocular development (in special hyphae pockets); includes subclasses Dothideomycetidae and Pleosporomycetidae; contains 10 orders.

        • Order Capnodiales (sooty molds)

          Grows on honeydew excreted by insects or on exudates on the leaves of plants; melanoid pigments in cell walls of hyphae; included in subclass Dothideomycetidae; example genera include Capnodium, Scorias, and Mycosphaerella.

        • Order Dothideales

          Forms lichens; asci borne in clusters in a locule; included in subclass Dothideomycetidae; example genera include Dothidea, Dothiora, Sydowia, and Stylodothis.

        • Order Hysteriales

          Found on woody branches of trees; stroma is boat-shaped, opening by a longitudinal slit that renders it apothecium-like; asci borne among pseudoparaphyses; example genera include Hysterium and Hysteropatella.

        • Order Jahnulales

          Found in freshwater environments; ascospores covered with sticky gelatin sheaths or apical appendages; hyphae adapted for attaching to wet substrates; example genera include Aliquandostipite, Jahnula, and Patescospora.

        • Order Myriangiales

          Parasitic on fungi and insects, epiphytic on leaves and stems; found mostly in tropical or subtropical regions; ascocarp present; asci borne singly in locules arranged at various levels in a globose stroma; included in subclass Dothideomycetidae; example genera include Myriangium and Elsinoe.

        • Order Pleosporales

          Forms lichens, some are pathogenic on plants; asci borne in a basal layer among pseudoparaphyses; included in subclass Pleosporomycetidae; example genera include Pleospora, Phaeosphaeria, Lophiostoma, Sporormiella, and Helminthosporium.

        • Order Botryosphaeriales (incertae sedis; not placed in any subclass)

          Pathogenic and endophytic in plants; ascospores are forcibly discharged; example genera include Botryosphaeria and Guignardia.

        • Order Microthyriales (incertae sedis; not placed in any subclass)

          Saprotrophic or epiphytic on stems and leaves.

        • Order Patellariales (incertae sedis; not placed in any subclass)

          Parasitic and saprotrophic; flask-shaped (perithecium-like) fruiting bodies; example genus is Patellaria.

        • Order Trypetheliales (incertae sedis; not placed in any subclass)

          Forms lichen; most have hyaline ascospores.

      • Class Eurotiomycetes

        Parasitic on animals, saprotrophic in soil; small, evanescent asci, found at various levels within spherical ascocarp; includes subclasses Chaetothyriomycetidae, Eurotiomycetidae, and Mycocaliciomycetidae; contains 7 orders.

        • Order Chaetothyriales

          Pathogenic in humans or saprotrophic on plants; ascocarps contain sterile filaments on the reproductive organs; included in subclass Chaetothyriomycetidae; example genera include Capronia, Ceramothyrium, and Chaetothyrium.

        • Order Pyrenulales

          Parasitic, saprotrophic, or symbiotic with algae to form lichens; asci evanescent; ascospores may be pigmented; included in subclass Chaetothyriomycetidae; example genera include Pyrenula and Pyrgillus.

        • Order Verrucariales

          Forms lichens on rocks and other substrates; perithecia (closed ascocarps with a pore in the top) have small depression-like spots on the surface; included in subclass Chaetothyriomycetidae; example genera include Agonimia, Dermatocarpon, Polyblastia, and Verrucaria.

        • Order Coryneliales

          Forms lichens; asci in ascostromata with funnel-shaped ostioles at maturity; included in subclass Eurotiomycetidae; examples of genera include Corynelia and Caliciopsis.

        • Order Eurotiales

          Parasitic in animals, saprotrophic in soil; asci evanescent; included in subclass Eurotiomycetidae; examples of genera include Eurotium, Penicillium, Talaromyces, Elaphomyces, Trichocoma, and Byssochlamys.

        • Order Onygenales

          Forms lichens; asci are formed in a mazaedium (a fruiting body consisting of a powdery mass of free spores interspersed with sterile threads, enclosed in a peridium or wall structure) and are evanescent; included in subclass Eurotiomycetidae; examples of genera include Onygena, Gymnoascus, Trichophyton, and Arthroderma.

        • Order Mycocaliciales

          Saprotrophic on lichens; includes nonlichenized calicioid fungi; ascomata stalked or sessile; included in subclass Mycocaliciomycetidae; examples of genera include Mycocalicium, Chaenothecopsis, Stenocybe, and Sphinctrina.

      • Class Laboulbeniomycetes

        Primarily parasitic on insects; contains 2 orders.

        • Order Laboulbeniales

          Parasitic on insects, including the true flies (order Diptera); ascospore attaches to and penetrates insect exoskeleton to absorb nutrients; spinelike ascoma; example genera include Laboulbenia, Rickia, and Ceratomyces.

        • Order Pyxidiophorales

          Ectoparasitic on mandibulate arthropods, may be mycoparasitic; mycelial; anamorphs lack vesiculate conidiophores; example genus includes Pyxidiophora.

      • Class Lecanoromycetes

        Forms lichens; thick ascal apex with narrow canal; includes subclasses Acarosporomycetidae, Lecanoromycetidae, and Ostropomycetidae; contains 10 orders.

        • Order Acarosporales

          Forms lichens; asci unitunicate and lecanoralean (resembling asci of the genus Lecanora), with nonamyloid or slightly amyloid inner ascus apex (tholus); included in subclass Acarosporomycetidae; example genera include Acarospora, Pleopsidium, and Sarcogyne.

        • Order Lecanorales

          Forms lichens; apothecia fruiting bodies; includes reindeer mosses, cup lichens, and beard lichens; included in subclass Lecanoromycetidae; example genera include Cladonia, Lecanora, Parmelia, Ramalina, and Usnea.

        • Order Peltigerales

          Forms lichens; thallus may be large and lobate; apothecia may be lecanorine or lecideine (darkened margin sometimes lacking a thalline margin); includes dog lichens; included in subclass Lecanoromycetidae; example genera include Coccocarpia, Collema, Nephroma, Pannaria, and Peltigera.

        • Order Teloschistales

          Forms lichens; found on rocks close to the sea; thallus sometimes composed of granules; may have poorly defined lobed margins; includes orange sea lichen and shore lichen (yellow scales); included in subclass Lecanoromycetidae; example genera include Caloplaca, Teloschistes, and Xanthoria.

        • Order Agyriales

          Forms lichens; thallus may be nonlobate; includes bullseye lichen and disk lichen; included in subclass Ostropomycetidae; examples of genera include Agyrium, Placopsis, Trapelia, and Trapeliopsis.

        • Order Baeomycetales

          Forms lichens; stalked or sessile ascomata; includes cap lichen; included in subclass Ostropomycetidae; example genus includes Baeomyces.

        • Order Ostropales

          Forms lichens; apothecia may be capitate-stipitate or sessile turbinate; includes dimple lichen, gomphillus lichen, and common script lichen; included in subclass Ostropomycetidae; examples of genera include Ostropa, Stictis, Gyalecta, Gomphillus, Graphis, Odontotrema, Porina, and Thelotrema.

        • Order Umbilicariales

          Forms lichens; grows on rocks; thallus is often foliose and is attached to substrate by an umbilicus; includes rock tripe; examples of genera include Lasallia and Umbilicaria.

        • Order Pertusariales

          Forms lichens; grows on rocks, mosses, and barks; primary thallus may be crustose, squamulose, or foliose; clustered or solitary apothecia; ascospores may be colourless; ascocarps may be absent; includes peppermint drop lichen; included in subclass Ostropomycetidae; examples of genera include Coccotrema, Icmadophila, Ochrolechia, and Pertusaria.

        • Order Candelariales (incertae sedis; not placed in any subclass)

          Forms lichens; commonly grows on rocks and shrubs; thallus is yellow to orange in colour; most are nitrophilus; apothecia may be lecanorine; thallus may be foliose; example genera include Candelaria and Candelariella.

      • Class Leotiomycetes

        Parasitic on plants, especially fruits; thin-walled, inoperculate asci, generally with amyloid apical rings; includes mildews; contains 5 orders.

        • Order Cyttariales

          Parasitic on plants, causes gall formation, especially on beech trees; spherical, dimpled ascocarps that are yellow to orange in colour; example genus includes Cyttaria.

        • Order Erysiphales (powdery mildews)

          Parasitic on plants; ascospores or conidia germinate on leaves and stems; mycelium septate, branched; example genera include Erysiphe, Blumeria, and Uncinula.

        • Order Helotiales

          Pathogenic on plants, saprotrophic, endophytic, mycorhizzal, mycoparasitic, or symbiotic on roots; inoperculate asci with distinct hymenium; apothecia disk-shaped to goblet-shaped; example genera include Dactylella, Hymenoscyphus, and Ascocoryne.

        • Order Rhytismatales

          Pathogenic on plants; asci have apical rings; ascomata develop in host tissue; ascospores long and thin; includes tar spot fungi; example genera include Rhytisma, Lophodermium, and Cudonia

        • Order Thelebolales

          Coprophilus (grows on dung); ascomata small, disk-shaped to globose; may have polysporus asci; example genera include Thelebolus, Coprotus, and Ascozonus.

      • Class Lichinomycetes

        Parasitic, saprotrophic, or symbiotic; inoperculate asci; includes peltula lichen; contains 1 order.

        • Order Lichinales

          Forms lichens; asci may be lecanoralean or prototunicate; example genera include Heppia, Lichina, and Peltula.

      • Class Orbiliomycetes

        Parasitic or saprotrophic, with many found on bark; includes some cup fungi; contains 1 order.

        • Order Orbiliales

          Parasitic on nematodes, non-lichen-forming; inoperculate ascus, may bifurcate and have a flexible stalk and truncated apex; example genera include Orbilia and Hyalorbilia.

      • Class Pezizomycetes

        Saprotrophic on wood, soil, or dung; unitunicate, operculate asci; includes some cup fungi; contains 1 order.

        • Order Pezizales

          Saprotrophic; amyloid asci; ascomata nonstalked, may be goblet-shaped or saucer-shaped; ascocarp may be operculate aboveground or be borne belowground; includes truffles; example genera include Peziza, Glaziella, Morchella, Pyronema, Terfezia, and Tuber.

      • Class Sordariomycetes

        Pathogenic on plants, causing canker formation, some are saprotrophic; ascomata typically perithecial with prominent ostioles and may be pear-shaped to globose; includes subclasses Hypocreomycetidae, Sordariomycetidae, and Xylariomycetidae; contains 19 orders.

        • Order Coronophorales

          Saprotrophic on wood; asci in ascostromata with irregular or round openings; ascomata sometimes covered with hairs (filaments); included in subclass Hypocreomycetidae; example genera include Nitschkia, Scortechinia, Bertia, and Chaetosphaerella.

        • Order Hypocreales

          Parasitic or pathogenic on plants, may cause canker formation; when present, perithecia and stromata are brightly coloured, soft, fleshy, or waxy; asci borne in a basal layer among apical paraphyses; included in subclass Hypocreomycetidae; example genera include Hypocrea, Nectria, Cordyceps, Claviceps, and Niesslia.

        • Order Melanosporales

          Mycoparasitic or saprotrophic; asci evanescent and unitunicate; perithecial or cleistothecial ascomata; included in subclass Hypocreomycetidae; example genus is Melanospora.

        • Order Microascales

          Parasitic on plants; asci evanescent (quickly deteriorating), borne at different levels in perithecia with ostioles, or sometimes with a long necklike structure terminating in a pore; included in subclass Hypocreomycetidae; example genera include Microascus, Petriella, Halosphaeria, Lignincola, and Nimbospora.

        • Order Boliniales

          Saprotrophic; ascocarp may be black and shiny; some with irregular stromata; included in subclass Sordariomycetidae; examples of genera include Camarops and Apiocamarops.

        • Order Calosphaeriales

          Saprotrophic; ascospores small; included in subclass Sordariomycetidae; examples of genera include Calosphaeria, Togniniella, and Pleurostoma.

        • Order Chaetosphaeriales

          Saprotrophic; ascomata subglobose to globose; paraphyses sparse to abundant; asci unitunicate, may lack apical ring; included in subclass Sordariomycetidae; examples of genera include Chaetosphaeria, Melanochaeta, Zignoëlla, and Striatosphaeria.

        • Order Coniochaetales

          Saprotrophic; ascomata subglobose to globose; filiform paraphyses; asci unitunicate; included in subclass Sordariomycetidae; examples of genera include Coniochaeta and Coniochaetidium.

        • Order Diaporthales

          Pathogenic on plants, causing chestnut blight, root rot, and black spot; paraphyses absent; asci free within ascomata; included in subclass Sordariomycetidae; examples of genera include Diaporthe, Gnomonia, Cryphonectria, and Valsa.

        • Order Ophiostomatales

          Pathogenic on plants, causing diseases such as Dutch elm disease and oak wilt; long, tubular ascomata with ostiole at the tip, through which spores are released; included in subclass Sordariomycetidae; examples of genera include Ophiostoma and Fragosphaeria.

        • Order Sordariales

          Mainly saprotrophic in soil and dung; ascomata solitary and perithecial; includes species commonly used in genetics research; included in subclass Sordariomycetidae; examples of genera include Sordaria, Podospora, Neurospora, Lasiosphaeria, and Chaetomium.

        • Order Xylariales

          Saprotrophic; inoperculate asci; some with white conidia; included in subclass Xylariomycetidae; examples of genera include Xylaria, Hypoxylon, Anthostomella, Diatrype, and Graphostroma.

        • Order Lulworthiales (incertae sedis; not placed in any subclass)

          Saprotrophic; ascomata subglobose to pear-shaped, paraphyses absent; asci unitunicate, thin-walled; example genera include Lulworthia and Lindra.

        • Order Meliolales (incertae sedis; not placed in any subclass)

          Lives on other organisms (biotrophic) in tropical regions; mycelium dark, superficial, typically bearing appendages (hyphopodia or setae); asci in basal layers in ostiolate perithecia without appendages; example genus includes Meliola.

        • Order Phyllachorales (incertae sedis; not placed in any subclass)

          Parasitic on plants and saprotrophic on salt marsh plants; some produce perithecia shielded inside a stroma, others do not produce a stroma; example genus is Phyllachora.

        • Order Trichosphaeriales (incertae sedis; not placed in any subclass)

          Pathogenic on plants, saprotrophic on wood; ascomata globose, dark, and superficial; cylindrical, stalked asci; some produce muriform (brick-shaped) spores; example genus is Trichosphaeria.

      • Pezizomycotina (incertae sedis; not placed in any class)

        • Order Lahmiales

          Pathogenic on trees, mainly aspens; example genus is Lahmia.

        • Order Medeolariales

          Saprotrophic; example genus is Medeolaria.

        • Order Triblidiales

          Saprotrophic; ascomata solitary or clustered; example genera include Huangshania, Pseudographis, and Triblidium.

  • Phylum Basidiomycota

    Parasitic or saprotrophic on plants or insects; filamentous; hyphae septate, with septa typically inflated (dolipore) and centrally perforated; mycelium of two types: primary consisting of uninucleate cells, succeeded by secondary consisting of dikaryotic cells, often bearing bridgelike clamp connections over the septa; asexual reproduction by fragmentation, oidia (thin-walled, free, hyphal cells behaving as spores), or conidia; sexual reproduction by fusion of hyphae (somatogamy), fusion of an oidium with a hypha (oidization), or fusion of a spermatium (a nonmotile male structure that empties its contents into a receptive female structure during plasmogamy) with a specialized receptive hypha (spermatization), resulting in dikaryotic hyphae that eventually give rise to basidia, either singly on the hyphae or in variously shaped basidiocarps (also called basidiomata); meiospores (basidiospores) borne on basidia; in the rusts and smuts, the dikaryotic hyphae produce teleutospores (thick-walled resting spores), which are a part of the basidial apparatus; this is a large phylum of fungi containing the rusts, smuts, jelly fungi, club fungi, coral and shelf fungi, mushrooms, puffballs, stinkhorns, and bird’s-nest fungi; sometimes included in the subkingdom Dikarya with its sister group, Ascomycota.

    • Subphylum Pucciniomycotina

      Pathogens of land plants; includes the rusts; contains eight classes.

      • Class Pucciniomycotina

        Parasitic on plants, some saprotrophic; contains 5 orders.

        • Order Septobasidiales

          Parasitic on plants, some members parasitic on or symbiotic with scale insects (order Homoptera); basidiospores germinate on insects, with haustoria coiled inside insect; example genera include Septobasidium and Auriculoscypha.

        • Order Pachnocybales

          Parasitic on plants; uninucleate basidiospores; singular conidia; hyphal cell wall ruptures during branching; example genus includes Pachnocybe.

        • Order Helicobasidiales

          Mycoparasitic; violet-coloured mycelia release powdery conidia when emerging; example genera include Helicobasidium and Tuberculina.

        • Order Platygloeales

          Parasitic on mosses and other plants; pycnium (fruiting body of rusts) forms masses of hyphae inside mosses; example genera include Platygloea and Eocronartium.

        • Order Pucciniales

          Parasitic on plants; typically have 5 spore stages and 2 alternate hosts; example genera include Puccinia and Uromyces.

      • Class Cystobasidiomycetes

        Parasitic on plants; simple-septate basidiomycetes; contains 3 orders.

        • Order Cystobasidiales

          Parasitic on plants; yeasts are non-teliospore-forming and produce auricularioid basidia and ballistospores (spores that are forcibly discharged); example genera include Cystobasidium, Occultifur, and Rhodotorula.

        • Order Erythrobasidiales

          Some are pathogenic in humans and animals, others are saprotrophic in soil or found in the air; yeastlike cells may be spherical or elongate; example genera include Erythrobasidium, Sporobolomyces, and Bannoa.

        • Order Naohideales

          Mycoparasitic; auricularoid basidia may contain mitospores; example genus is Naohidea.

      • Class Agaricostilbomycetes

        Parasitic or saprotrophic; simple-septate basidiomycetes; contains 2 orders.

        • Order Agaricostilbales

          Mostly saprotrophic; fruiting body is septate, with uniform hyphae; some have slender basidiospores, which may germinate by budding and may be solitary or clustered; example genera include Agaricostilbum and Chionosphaera.

        • Order Spiculogloeales

          Parasitic or saprotrophic; spinulose to granulose auricularoid basidia; include jelly fungi; example genera include Mycogloea and Spiculogloea.

      • Class Microbotryomycetes

        Pathogenic in plants, some are mycoparasitic; includes some yeasts; contains 4 orders.

        • Order Heterogastridiales

          Mycoparasitic; basidiocarps may be pycnidioid; example genus includes Heterogastridium.

        • Order Microbotryales

          Pathogenic in plants (some cause smut); violet teliospores; example genera include Microbotryum and Ustilentyloma.

        • Order Leucosporidiales

          Mycoparasitic; mycelia lack clamp connections; septate basidia; example genera include Leucosporidiella, Leucosporidium, and Mastigobasidium.

        • Order Sporidiales

          Nonpathogenic; basidia may be very long; hyphae with clamp connections; some species emit peachlike odour; example genera include Sporidiobolus and Rhodosporidium.

      • Class Atractiellomycetes

        Parasitic or saprotrophic; simple septate; some pycnidial members; auricularoid basidia; gastroid; contains 1 order.

        • Order Atractiellales

          Parasitic or saprotrophic; minute globuse conidia formed from tips of hyphae; example genera include Atractiella, Saccoblastia, Helicogloea, and Phleogena.

      • Class Classiculomycetes

        Parasitic; uredinalian septal pores with tremelloid haustorial cells; contains 1 order.

        • Order Classiculales

          Saprotrophic; many are aquatic or aeroaquatic hyphomycetes; simple septal pores; some with long fusiform basidiospores; example genera include Classicula and Jaculispora.

      • Class Mixiomycetes

        Parasitic or saprotrophic; simple septate; contains 1 order.

        • Order Mixiales

          Parasitic primarily on ferns; blastosporic yeasts; example genus is Mixia.

      • Class Cryptomycocolacomycetes

        Parasitic; simple septate; contains 1 order.

        • Order Cryptomycocolacales

          Parasitic on insects such as bark beetles, some are mycoparasitic; sometimes fuse with host cells using a small pore in colacosome; example genera include Cryptomycocolax and Colacosiphon.

    • Subphylum Ustilaginomycotina

      Parasitic on plants as dikaryotic hyphae; haploid yeast phase is saprotrophic; contains 2 classes.

      • Class Ustilaginomycetes

        Parasitic (dikaryotic phase) and saprotrophic (haploid phase); includes smut fungi; contains 3 orders.

        • Order Urocystales

          Parasitic on plants such as arrowhead, causing blister smut, and wheat, causing flag smut; mycelia may form dense clusters in leaves and leaf stalks (petioles); example genera include Urocystis, Ustacystis, and Doassansiopsis.

        • Order Ustilaginales

          Parasitic on plants, causing smut of many cereal grains, including wheat, barley, corn, and rice; masses of spores (sori) are usually black and dusty; basidial apparatus consisting of thick-walled teleutospore (probasidium), which upon germination gives rise to a septate or nonseptate tube (metabasidium) bearing basidiospores; basidiospores not forcibly discharged, germinating usually by budding or by fusing and then producing a mycelial germ tube; example genera include Ustilago and Cintractia.

      • Class Exobasidiomycetes

        Parasitic and pathogenic on plants; includes smut fungi; contains 7 orders.

        • Order Doassansiales

          Parasitic on plants; holobasidia (single-celled, may be club-shaped); teliosporic; example genera include Doassansia, Rhamphospora, and Nannfeldtiomyces.

        • Order Entylomatales

          Parasitic and pathogenic on plants, causing rice leaf smut and dahlia smut; ballistospore-forming; example genera include Entyloma and Tilletiopsis.

        • Order Exobasidiales

          Parasitic and pathogenic on vascular plants; lacking basidiocarps; basidia produced in a layer on the surface of parasitized plants; example genera include Exobasidium, Clinoconidium, and Dicellomyces.

        • Order Georgefischeriales

          Parasitic on plants; holobasidia; may reproduce sexually in teleomorphic phase; example genera include Georgefischeria, Phragmotaenium, Tilletiaria, and Tilletiopsis.

        • Order Malasseziales

          Symbiotic on skin of animals but can become pathogenic, mainly affecting dogs and cats; asexual; rapidly budding yeasts with thick cell walls, colonies range in colour from cream to yellow, brown, or orange; conidia are globose to elliptical-shaped; example genus is Malassezia.

        • Order Microstromatales

          Parasitic on plants, some found in the nectar of orchids; some are nonteliosporic; some are anamorphic yeasts lacking septal pores; example genera include Microstroma, Sympodiomycopsis, and Volvocisporium.

        • Order Tilletiales

          Parasitic on grasses (family Poaceae); ballistospore-forming; primary basidiospores may conjugate, forming dikaryon capable of infecting hosts; example genera include Tilletia, Conidiosporomyces, and Erratomyces.

    • Subphylum Agaricomycotina

      Parasitic or symbiotic on plants, animals, and other fungi, some are saprotrophic or mycorrhizal; basidia may be undivided or have transverse or longitudinal septa; dolipore (inflated) septa and septal pore cap (parenthesomes) present; includes mushrooms, bracket fungi, puffballs; contains 3 classes.

      • Class Tremellomycetes

        Parasitic or saprotrophic; if present, parenthesome separated into cup-shaped sections; gelatinous fruiting bodies may be absent; includes 3 orders.

        • Order Cystofilobasidiales

          Parasitic and pathogenic on plants (causing black canker of parsnips), may be saprotrophic; dolipores present; may lack parenthesomes; unicellular yeasts; example genera include Cystofilobasidium, Mrakia, and Itersonilia.

        • Order Filobasidiales

          Pathogenic in humans, causing cryptococcosis, parasitic on fungi, insects, and humans, saprotrophic in soil and dung; mitosporic; asexual reproduction as yeasts, which are encapsulated, with colonies ranging in colour from cream to pink, yellow, or brown; sexual reproduction as teleomorph; example genera include Filobasidiella and Cryptococcus.

        • Order Tremellales

          Parasitic on mosses, vascular plants, or insects, although most are saprotrophic; basidiocarps well-formed, appearing as inconspicuous horny crusts when dry but usually bright-coloured to black gelatinous masses after a rain; example genera include Tremella, Trichosporon, and Christiansenia.

      • Class Dacrymycetes

        Mostly saprotrophic; parenthesome imperforate (forms a dome-shaped cover over dolipore); contains 1 order.

        • Order Dacrymycetales

          Saprotrophic; some with “tuning fork” basidia; some with fruiting bodies ranging from cup-shaped to cone-shaped; example genera include Dacrymyces, Calocera, and Guepiniopsis.

      • Class Agaricomycetes

        Parasitic, pathogenic, symbiotic, or saprotrophic; most are terrestrial, with few aquatic members; all are mushroom-forming; parenthesomes imperforate or perforate (spore cap has openings); includes subclasses Agaricomycetidae and Phallomycetidae; contains 17 orders.

        • Order Agaricales

          Most are saprotrophic, some are parasitic on plants (causing root rot), others are mycorrhizal; basidia produced in layers (hymenia) on the underside of fleshy fruiting bodies (basidiocarps), in tubes (boletes), or on gills (mushrooms); includes inky cap mushrooms and some species of earthstars and puffballs in the family Lycoperdaceae; included in subclass Agaricomycetidae; example genera include Agaricus, Armillaria, Coprinus, and Pleurotus.

        • Order Atheliales

          Mycorrhizal, found primarily on conifers and hardwood trees; included in subclass Agaricomycetidae; example genera include Athelia, Piloderma, and Tylospora.

        • Order Boletales

          Saprotrophic, many are found living at the base of trees such as pines; spores enclosed in fruiting body, become dusty at maturity and are expelled into the air; includes some edible boletes, such as butter boletes, king boletes, and queen boletes, as well as pigskin poison puffballs; included in subclass Agaricomycetidae; example genera include Boletus, Scleroderma, Coniophora, and Rhizopogon.

        • Order Geastrales

          Found under trees, mainly conifers; spherical or egg-shaped fruiting bodies resemble mushrooms, some become star-shaped after splitting open to release spores; includes earthstars; included in subclass Phallomycetidae; example genera include Geastrum, Radiigera, and Sphaerobolus.

        • Order Gomphales

          Most are mycorrhizal, some are saprotrophic; spores may be olive-shaped, usually rough; included in subclass Phallomycetidae; example genera include Gomphus, Gautieria, and Ramaria.

        • Order Hysterangiales

          Most are saprotrophic; resembles puffballs when small, becoming pear-shaped and finally globose when mature; fruiting body may be pink to vibrant lilac in colour; mature internal tissue characterized by fetid odour; includes club-shaped stinkhorn; included in subclass Phallomycetidae; example genera include Hysterangium, Phallogaster, Gallacea, and Austrogautieria.

        • Order Phallales

          Found in temperate zones; phalluslike fruiting body with fetid odour, often slimy; includes stinkhorns; included in subclass Phallomycetidae; example genera include Phallus, Clathrus, and Claustula.

        • Order Auriculariales (incertae sedis; not placed in any subclass)

          Saprotrophic; basidia may be divided longitudinally; gelatinous fruiting body may appear to be upside-down and may fuse to form large masses; includes ear fungus and black jelly roll; example genera include Auricularia, Exidia, and Bourdotia.

        • Order Cantharellales (incertae sedis; not placed in any subclass)

          Saprotrophic; basidia have unusual shapes; hyphae may be thin-walled or thick-walled, with or without clamp connections; example genera include Cantharellus, Botryobasidium, Craterellus, and Tulasnella.

        • Order Corticiales (incertae sedis; not placed in any subclass)

          Parasitic, saprotrophic, or symbiotic with algae to form lichen; spores range in colour from white to pink; hyphae clamped; example genera include Corticium, Vuilleminia, and Punctularia.

        • Order Gloeophyllales (incertae sedis; not placed in any subclass)

          Saprotrophic; many cause wood rot; basidiospores may be cylindrical to ellipsoidal in shape; hyphae clamped; example genera include Gloeophyllum, Neolentinus, and Veluticeps.

        • Order Hymenochaetales (incertae sedis; not placed in any subclass)

          Mycorrhizal or saprotrophic; many cause white rot; fruiting body may be inconspicuous; many with imperforate parenthesome; example genera include Hymenochaete, Phellinus, and Trichaptum.

        • Order Polyporales (incertae sedis; not placed in any subclass)

          Mycorrhizal or saprotrophic, often found on decaying wood; basidia borne in various ways but rarely on gills; fruiting body may be mushroomlike; example genera include Polyporus, Fomitopsis, and Phanerochaete.

        • Order Russulales (incertae sedis; not placed in any subclass)

          Parasitic or saprotrophic, often found at the base of trees; fruiting body may be slimy; many have gills; some are very large, reaching a diameter of 1 metre (3.3 feet); includes some edible fungi, such as some species of tooth fungi; example genera include Russula, Aleurodiscus, Bondarzewia, Hericium, Peniophora, and Stereum.

        • Order Sebacinales (incertae sedis; not placed in any subclass)

          Symbiotic with plants, some form mycorrhizal associations; forms hyphal networks on and within roots; chlamydospores generated inside root cells or at root surface; example genera include Sebacina, Tremellodendron, and Piriformospora.

        • Order Thelephorales (incertae sedis; not placed in any subclass)

          Found in the ground in wooded areas; fruiting bodies black to brown; hyphae usually have clamp connections; example genera include Thelephora, Bankera, and Polyozellus.

        • Order Trechisporales (incertae sedis; not placed in any subclass)

          Found on wood or in soil; clavate (club-shaped) or stipitate (stalk-shaped) basidiomata; hyphae with clamp connections; example genera include Trechispora, Sistotremastrum, and Porpomyces.

    • Basidiomycota (incertae sedis)

      Includes basidiomycota not placed in a subphylum; contains 2 classes.

      • Class Wallemiomycetes

        Includes molds that are pathogenic in humans; osmophilic (capable of living on surfaces with highly concentrated solutes, such as salt or sugar); contains 1 order.

        • Order Wallemiales

          Pathogenic in humans, contains known allergens; found in soil, hay, and textiles; spores are typically brown in colour and formed in chains; example genus is Wallemia.

      • Class Entorrhizomycetes

        Pathogenic or saprotrophic on roots of plants; contains 1 order.

        • Order Entorrhizales

          Pathogenic or saprotrophic; hyphae clamped; dolipore and parenthesome present; contains the only smut fungus that causes gall formation on roots; example genus is Entorrhiza.

• Kingdom Chromista

  Common microorganisms; includes important plant pathogens, such as the cause of potato blight (Phytophthora); motile spores swim by means of 2 flagella and grow as hyphae with cellulose-containing walls; includes the majority of the Oomycota; contains a total of approximately 110 genera and 900 species.

  • Phylum Hyphochytriomycota

    Microscopic organisms that are parasitic or saprotrophic on algae and fungi in fresh water and in soil; forms a small thallus, often with branched rhizoids; whole of the thallus is eventually converted into a reproductive structure; contains 23 species in 6 genera.

    • Order Hyphochytriales

      Mostly marine; motile cells bear a single tinsel flagellum (a flagellum with short side branches along the central axis, comblike); example genera include Hyphochytrium and Rhizidiomyces.

  • Phylum Labyrinthulomycota

    Found in both salt water and fresh water in association with algae and other chromists; feeding stage comprises an ectoplasmic network and spindle-shaped or spherical cells that move within the network by gliding over one another; contains about 45 species in 10 genera.

    • Order Labyrinthulales

      Parasitic on marine algae, symbiotic with algae or vascular plants, parasitic on plants, or saprotrophic in soil; motile cells glide on an extracellular matrix secreted by an organelle known as a sagenogenetosome; example genus is Labyrinthula.

    • Order Thraustochytriales

      Found in fresh water and salt water, as well as in saline soil; secrete ectoplasmic nets from a sagenogenetosome; monocentric thallus; example genus is Thraustochytrium.

  • Phylum Oomycota

    Found in fresh water, wet soil, and marine habitats, some are pathogenic (such as Saprolegnia and Phytophthora); contains about 600 species in 90 genera.

    • Order Leptomitales

      Aquatic, saprotrophic, often found in polluted water; eucarpic; hyphae constricted, with cellulin plugs, arising from a well-defined basal cell; oogonium typically containing a single egg, which may be free or embedded in periplasm (a peripheral layer of protoplasm); example genera include Apodachlyella, Ducellieria, Leptolegniella, and Leptomitus.

    • Order Myzocytiopsidales

      Pathogenic in insects of the order Diptera; spores develop within a sporangium; example genus is Crypticola.

    • Order Olpidiopsidales

      Pathogenic on marine plants, including laver (nori); thallus infects cells of host; example genus is Olpidiopsis.

    • Order Peronosporales

      Aquatic or terrestrial; parasitic on algae or vascular plants, the latter mostly obligate parasites causing downy mildews; in advanced species, zoosporangia borne on well-differentiated sporangiophores, deciduous and behaving as conidia (asexually produced spores); example genera include Albugo, Peronospora, Bremia, and Plasmopara.

    • Order Pythiales

      Pathogenic in plants, algae, and fungi, some are saprotrophic in soil or water; hyphae may grow within or between cells of plants, causing root rot; example genera include Pythium, Phytophthora, and Pythiogeton.

    • Order Rhipidiales

      Aquatic, saprotrophic, often found in polluted waters; thallus contains cellulin plugs, usually branched and inflated; example genus is Rhipidium.

    • Order Salilagenidiales

      Marine, parasitic on prawns and lobsters; mycelia penetrate exoskeleton; example genus is Haliphthoros.

    • Order Saprolegniales (water molds)

      Parasitic or saprotrophic; some cause root rot, others infect fish and fish eggs; mostly eucarpic, filamentous water molds or soil fungi; hyphae without constrictions or cellulin plugs; oogonia containing 1 to many eggs; some species are diplanetic, producing 2 types of zoospores (primary pear-shaped spores with anterior flagella and secondary kidney-shaped spores with lateral flagella); example genera include Leptolegnia, Achlya, and Saprolegnia.

    • Order Sclerosporales

      Parasitic on plants, causing root rot; can survive in soil for long periods of time; thick-walled oogonia; may lack haustoria; example genera include Sclerospora and Verrucalvus.

    • Order Anisolpidiales

      Found in marine environments, parasitic; example genus is Anisolpidium.

    • Order Lagenismatales

      Found in marine environments, parasitic; filamentous; example genus is Lagenisma.

    • Order Rozellopsidales

      Found in marine environments, parasitic on euglena, some are biotrophic with other Oomycota or algae; may have naked thalli; example genera include Pseudosphaerita and Rozellopsis.

    • Order Haptoglossales

      Parasitic on algae or plant roots, including roots of sugar beets; may be non-mycelial-forming; sporangia develop inside host cells; example genera include Haptoglossa, Lagena, and Pontisma.

Critical appraisal

Fungi were once considered plants. However, nearly all fungal cell walls contain chitin, which is also found in the exoskeletons of many invertebrate animals. In addition, both chytrid zoospores and animal sperm share in common the presence of a single posterior flagellum. As a result of these differences and extensive molecular sequence comparisons, animals and fungi are considered to be sister groups. Some scientists include animals and fungi in a common ancestor clade, called the opisthokont clade (opistho meaning posterior and kont meaning flagellum). The classification presented above reflects the division of fungi on the basis of phylogenetic relationships and is generally agreed upon. However, there remain many orders for which no general consensus has been reached regarding inclusion in classes, subclasses, or subphyla.