The Boletaceae are a family of mushroom-forming fungi, primarily characterised by small pores on the spore-bearing hymenial surface (at the underside of the mushroom), instead of gills as are found in most agarics. Nearly as widely distributed as the agarics, the family is renowned for hosting some prime edible species highly sought after by mushroom hunters worldwide, such as the cep or king bolete (Boletus edulis). A number of rare or threatened species are also present in the family, that have become the focus of increasing conservation concerns. As a whole, the typical members of the family are commonly known as boletes.
Boletes are a group of mushrooms reasonably safe for human consumption, as none of them are known to be deadly to adults. Edible bolete species are especially suitable for novice collectors, since they pose little danger of being confused with deadly poisonous mushrooms, such as deadly Amanita species which bear gills instead of pores in their hymenial surface. Some boletes are toxic and may cause gastrointestinal poisoning if consumed, but these are unlikely to be confused with popular edible species in the family.
The family has been the subject of extensive systematic revisions in recent years, as some of the early established genera (particularly Boletus, Leccinum and Xerocomus), have revealed to be highly polyphyletic, and the original number of genera within the family had been underestimated. As a result, several new species and genera have been described from Asia, Europe and North America, while many existing species have been transferred to different genera, in concordance with phylogenetic results.
Description
Most species of Boletaceae produce large, fleshy mushrooms, with a more or less central stipe. The fruit bodies typically have tubular hymenophores, although a small number of species (e.g. Phylloporus) are lamellate. The spore deposit colours are commonly olivaceous (yellowish-green), yellowish, brownish, or vinaceous (red-wine coloured), and when viewed under the microscope spores are usually fusiform or subfusiform. In many species, parts of the fruit body will turn blue, red, or black when bruised or exposed to the air, as a result of the oxidation of pulvinic acid derivatives, like variegatic, xerocomic, and atrotomentinic acids.
Taxonomy Boletaceae were first described by the French botanist François Fulgis Chevallier in 1826, as a family distinct from Agaricaceae. Five genera were initially included in Chevallier's circumscription: Boletus (which is the type genus of the family), Cladoporus (now synonymous with LaetiporusKirk et al., (2008), p. 146.), Physisporus (now PerenniporiaKirk et al., (2008), p. 535.), Polyporus, and Fistulina. However, all of the original genera except Boletus have since been transferred to different families, and several new Boletaceae genera have been described.
Genera Rolf Singer, in the 4th edition (1986) of his Agaricales in Modern Taxonomy, included 26 genera and 415 species in Boletaceae. In the Dictionary of the Fungi (10th edition, 2008), 35 Boletaceae genera were recognised, which collectively contained 787 species.Kirk et al. (2008), p. 96. Molecular phylogenetic studies in the 2000s have revised the concept of the family; in a highly cited 2006 publication, Manfred Binder and David Hibbett recognised 38 genera within the family, many of which had remained at the time undescribed. The number of Boletaceae genera increased significantly in the following years, as some of the early-established genera (Boletus, Leccinum, Xerocomus), further revealed to be highly polyphyletic. In the comprehensive work of Wu and colleagues (2014), seven major clades at subfamily level and 59 generic lineages were uncovered, including four new subfamilies (Austroboletoideae, Chalciporoideae, Leccinoideae, and Zangioideae) and 22 potential new genera. To formally name the generic lineages unravelled by molecular phylogenies, several new genera have since been described from Asia, Europe and North America including, among others, Baorangia, Butyriboletus, Cacaoporus, Caloboletus, Exsudoporus, Imperator and Rubroboletus.
Some characters traditionally emphasised in morphology-based taxonomy, such as basidiospore ornamentation and "stuffed" pore morphology, revealed to be incongruent with molecular taxonomy, suggesting that certain traits evolved more than once within the family.
GenusAuthority YearNo. of speciesDistributionAfroboletusPegler & T.W.K.Young 19817tropical AfricaAlessioporusGelardi, Vizzini & Simonini 20141southern EuropeAureoboletusPouzar 195717widespreadAustralopilusHalling & Fechner 20121AustraliaAustroboletusWolfe 1980America, AustralasiaBaorangiaG. Wu & Zhu L. Yang 2015East Asia, North AmericaBoletellusMurrill 1909widespreadBoletochaeteSinger 19443 Africa, Southeast AsiaBoletusFr. 1821widespreadBorofutusHosen & Zhu L.Yang 20121 BangladeshBothiaHalling, T.J.Baroni, & Binder 20071 North AmericaBuchwaldoboletusPilát 19623 Europe, AustraliaButyriboletusD.Arora & J.L.Frank 201418widespreadCacaoporusRaspé & Vadthanarat 20192ThailandCaloboletusVizzini 201413widespreadChalciporusBataille 190825widespreadChamonixiaRolland 18998 widespreadCorneroboletus N.K.Zeng & Zhu L.Yang 20121 Singapore, Malaysia, tropical ChinaCrocinoboletus N.K. Zeng, Zhu L. Yang & G. Wu 20152 East Asia, South AsiaCyanoboletus Gelardi, Vizzini & Simonini 2014 3 widespreadDurianella A.W.Wilson & Manfr.Binder 2008 1 Malaysia, BorneoErythrophylloporus Raspé, Vadthanarat & Lumyong 2019 3China, ThailandExsudoporus Vizzini, Simonini & Gelardi 2014 3North America, EuropeFistulinellaHenn. 190115pantropicalGastroboletusLohwag 196213widespreadGastroleccinumThiers 19891North AmericaHarrya Halling, Nuhn & Osmundson 2012 2Asia, North America, Central AmericaHeimioporusE.Horak 2004widespreadHeliogaster(Kobayasi) Orihara & Iwase 20101JapanHemileccinumŠutara 20083Europe, North AmericaHortiboletusSimonini, Vizzini & Gelardi 20154Europe, North AmericaImleriaVizzini 20144Europe, Asia, North AmericaImperatorAssyov et al. 2015 3Europe, West AsiaKaziboletusIqbal Hosen, Zhu L.Yang 20211South AsiaLanmaoaG. Wu, Zhu L. Yang, Halling 2015>5East Asia, North AmericaLeccinellumBresinsky & Manfr. Binder 200310widespreadLeccinumGray 1821widespreadMucilopilusWolfe 19794North America, New ZealandMycoamaranthusCastellano, Trappe & Malajczuk 19923Australasia, Africa, Southeast AsiaNeoboletusGelardi et al. 20149Europe, AsiaNigroboletusGelardi, Vizzini, E. Horak, T.H. Li & Ming Zhang 20151ChinaOctavianiaVittad. 183115widespreadParvixerocomusG. Wu & Zhu L. Yang, 20152East AsiaPaxillogasterE.Horak 19661South AmericaPhylloboletellusSinger 19521 Central and South AmericaPhyllobolitesSinger 19421South AmericaPhylloporusQuel. 1888cosmopolitanPseudoaustroboletus Yan C. Li & Zhu L. Yang 20141East Asia, South AsiaPseudoboletusŠutara 19912north temperate regionsPulchroboletusVizzini, Simonini & Gelardi 20141southern EuropePulveroboletusMurrill 190925cosmopolitanRetiboletusManfr. Binder & Bresinsky 20025 north temperate regionsRheubarbariboletusVizzini, Simonini & Gelardi 20152 EuropeRhodactinaPegler & T.W.K.Young 19892India, ThailandRossbeeveraT.Lebel & Orihara 20119Asia, AustraliaRoyoungiaCastellano, Trappe & Malajczuk 19921AustraliaRubroboletus Kuan Zhao & Zhu L.Yang 20148WidespreadRugiboletusG. Wu & Zhu L. Yang 20152East AsiaSetogyroporusHeinem. & Rammeloo 19991tropical AfricaSingerocomusT.W.Henkel & M.E.Sm. 20163 ??SingeromycesM.M.Moser 19661ArgentinaSinoboletusM.Zang 199210ChinaSirindhorneaLueangjaroenkit et al.20251ThailandSolioccasusTrappe, Osmundson, Manfr.Binder, Castellano & Halling 20131AustralasiaSpongiformaDesjardin, Manf. Binder, Roekring & Flegel 20092Thailand, MalaysiaStrobilomycesBerk. 1851cosmopolitanSuillellusMurrill 190911North America, EuropeSutorius Halling, Nuhn & Fechner 20123North America, Costa Rica, Africa, S.E. Asia, AustraliaTubosaetaE.Horak 19675Africa, AsiaTylopilusP.Karst 1881widespreadVeloporphyrellus L.D.Gómez & Singer 19841Central AmericaWakefieldia Corner & Hawker 19522Asia, EuropeXanthoconiumSinger 19447cosmopolitanXerocomellus Šutara 200824North and South America, EuropeXerocomusQuel1887>20widespreadZangia Yan C.Li & Zhu L.Yang 2011 6 China
(*) Note that the phylogenetic and taxonomic position of many taxa currently remaining in genus Boletus has not yet been clarified. The number of species in this genus will therefore significantly reduce in the following years, as more taxa will be transferred to different genera, or found to be synonyms.
Many other genera formerly part of this family have been moved into other, smaller families, as work with molecular phylogeny shows that they are more distantly related, even if morphologically similar. Representative of this adjustment, is the move of the slimy-capped genus Suillus to the family Suillaceae.
Distribution
Boletes are found worldwide, on every continent except Antarctica. Well-known and well-described in the temperate latitudes in the northern hemisphere, newer research has shown significant diversity in tropical and southern hemisphere regions as well. E. J. H. Corner found evidence of at least 60 species on the island of Singapore alone. In 1972 he described 140 species from the Malay Peninsula and Borneo and estimated there were at least as many yet to be documented. Over 100 species belonging to 52 genera have been reported from China, which has emerged as one of the worldwide hotspots of Boletaceae diversity. The family is also reasonably well-represented in the Mediterranean region, where many rare or range-restricted species can be found.
Ecology
As heterotrophic organisms, the majority Boletaceae species are symbiotic, and form mutually beneficial ectomycorrhizal associations with various trees and shrubs. However, a number of ancestral species in genera Buchwaldoboletus and Pseudoboletus, are saprotrophic or parasitic. Evidence suggests that some, if not all, species of Chalciporus might also have a mycoparasitic interaction with other fungi. The exact trophic status of some South American and African boletes, such as species of Phylloboletellus, is nonetheless not yet fully clarified, as fruit bodies are often found without the presence of ectomycorrhizal vegetation.
Most frequently associated tree-hosts are members of the Fagaceae, particularly oak (Quercus), beech (Fagus) and chestnut (Castanea). Fewer species are associated with conifers, mostly spruce (Picea) and fir (Abies). In the Mediterranean region, most boletes are strongly associated with evergreen oaks, particularly members of the "Ilex" group, such as the holm oak (Quercus ilex), the kermes oak (Q. coccifera), or the golden oak (Q. alnifolia). Some boletes are also known to grow in association with Cistaceae shrubs, mainly Cistus and Helianthemum, and at least one species (Leccinellum corsicum) is exclusively associated with rockrose.
Most boletes are sensitive to cold and fruit during warm spells in the summer and early months of the autumn, while some have very specific preferences with regards to substrate. For instance, the highly sought after Boletus aereus is mostly found on acidic soils, whereas the poisonous Rubroboletus satanas is predominantly calciphilous and mostly occurs on chalk. Other species, such as Hemileccinum impolitum or Leccinellum lepidum, are indifferent to the substrate and frequently occur on both calcareous and acidic soil.