Boletaceae

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.<ref name=Nelson2010/>

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 Laetiporus<ref>Kirk et al., (2008), p. 146.</ref>), Physisporus (now Perenniporia<ref>Kirk et al., (2008), p. 535.</ref>), Polyporus, and Fistulina.<ref name=Chevallier1828/> However, all of the original genera except Boletus have since been transferred to different families,<ref name="Donk 1964"/><ref name=Singer1986/> 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.<ref name=Singer1986/> In the Dictionary of the Fungi (10th edition, 2008), 35 Boletaceae genera were recognised, which collectively contained 787 species.<ref>Kirk et al. (2008), p. 96.</ref> 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.<ref name=Binder2006/> 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.<ref name="Nuhn 2013"/> In the comprehensive work of Wu and colleagues (2014),<ref name="Wu 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,<ref name="Wu 2015"/> Butyriboletus,<ref name="Arora 2014"/> Cacaoporus,<ref name="Vadthanarat 2019"/> Caloboletus,<ref name="Vizzini 2014a"/> Exsudoporus,<ref name="Vizzini 2014c"/> Imperator<ref name="Assyov 2015"/> and Rubroboletus.<ref name="Zhao 2014"/>

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.<ref name="Wu 2014"/><ref name="Wu et al. 2016"/>

Genus	Authority	Year	No. of species	Distribution
Afroboletus	Pegler & T.W.K.Young	1981	7	tropical Africa
Alessioporus<ref name="Gelardi 2014"/>	Gelardi, Vizzini & Simonini	2014	1	southern Europe
Aureoboletus	Pouzar	1957	17<ref name="Halling 2015"/>	widespread
Australopilus<ref name="Halling 2012b"/>	Halling & Fechner	2012	1	Australia
Austroboletus	Wolfe	1980	Template:Sort	America, Australasia
Baorangia<ref name="Wu 2015"/>	G. Wu & Zhu L. Yang	2015	Template:Sort	East Asia, North America
Boletellus	Murrill	1909	Template:Sort	widespread
Boletochaete	Singer	1944	3	Africa, Southeast Asia
Boletus	Fr.	1821	Template:Sort	widespread
Borofutus<ref name="Hosen 2013"/>	Hosen & Zhu L.Yang	2012	1	Bangladesh
Bothia	Halling, T.J.Baroni, & Binder	2007	1	North America
Buchwaldoboletus	Pilát	1962	3	Europe, Australia
Butyriboletus<ref name="Arora 2014"/>	D.Arora & J.L.Frank	2014	18	widespread
Cacaoporus<ref name="Vadthanarat 2019"/>	Raspé & Vadthanarat	2019	2	Thailand
Caloboletus<ref name="Vizzini 2014a"/>	Vizzini	2014	13	widespread
Chalciporus	Bataille	1908	25	widespread
Chamonixia	Rolland	1899	8	widespread
Corneroboletus<ref name="Zeng 2012"/>	N.K.Zeng & Zhu L.Yang	2012	1	Singapore, Malaysia, tropical China
Crocinoboletus<ref name="Zeng 2014"/>	N.K. Zeng, Zhu L. Yang & G. Wu	2015	2	East Asia, South Asia
Cyanoboletus<ref name="Vizzini 2014d"/>	Gelardi, Vizzini & Simonini	2014	3	widespread
Durianella<ref name="Desjardin 2010"/>	A.W.Wilson & Manfr.Binder	2008	1	Malaysia, Borneo
Erythrophylloporus<ref name="Vadthanarat 2019b"/>	Raspé, Vadthanarat & Lumyong	2019	3	China, Thailand
Exsudoporus<ref name="Vizzini 2014c"/>	Vizzini, Simonini & Gelardi	2014	3	North America, Europe
Fistulinella	Henn.	1901	15	pantropical
Gastroboletus	Lohwag	1962	13	widespread
Gastroleccinum	Thiers	1989	1	North America
Harrya<ref name="Halling 2012b"/>	Halling, Nuhn & Osmundson	2012	2	Asia, North America, Central America
Heimioporus	E.Horak	2004	Template:Sort	widespread
Heliogaster<ref name=Orihara2010/>	(Kobayasi) Orihara & Iwase	2010	1	Japan
Hemileccinum<ref name="Šutara 2008"/>	Šutara	2008	3<ref name="Halling 2015"/>	Europe, North America<ref name="Halling 2015"/>
Hortiboletus<ref name="Vizzini 2015"/>	Simonini, Vizzini & Gelardi	2015	4	Europe, North America
Imleria<ref name="Vizzini 2014b"/>	Vizzini	2014	4<ref name="Zhu2014"/>	Europe, Asia, North America<ref name="Zhu2014"/>
Imperator	Assyov et al.	2015	3	Europe, West Asia
Kaziboletus<ref name="Hosen 2021">Template:Cite journal</ref>	Iqbal Hosen, Zhu L.Yang	2021	1	South Asia
Lanmaoa<ref name="Wu 2015"/>	G. Wu, Zhu L. Yang, Halling	2015	>5	East Asia, North America
Leccinellum	Bresinsky & Manfr. Binder	2003	10	widespread
Leccinum	Gray	1821	Template:Sort	widespread
Mucilopilus<ref name="Wu 2014"/>	Wolfe	1979	4<ref name=Wolfe1979/>	North America, New Zealand<ref name=Wolfe1979/>
Mycoamaranthus	Castellano, Trappe & Malajczuk	1992	3	Australasia, Africa, Southeast Asia
Neoboletus	Gelardi et al.	2014	9	Europe, Asia
Nigroboletus<ref name="Gelardi 2015"/>	Gelardi, Vizzini, E. Horak, T.H. Li & Ming Zhang	2015	1	China
Octaviania	Vittad.	1831	15	widespread
Parvixerocomus<ref name="Wu 2015"/>	G. Wu & Zhu L. Yang,	2015	2	East Asia
Paxillogaster	E.Horak	1966	1	South America
Phylloboletellus	Singer	1952	1	Central and South America
Phyllobolites	Singer	1942	1	South America
Phylloporus	Quel.	1888	Template:Sort	cosmopolitan
Pseudoaustroboletus<ref name="Li2014"/>	Yan C. Li & Zhu L. Yang	2014	1	East Asia, South Asia
Pseudoboletus	Šutara	1991	2	north temperate regions
Pulchroboletus<ref name="Gelardi 2014"/>	Vizzini, Simonini & Gelardi	2014	1	southern Europe
Pulveroboletus	Murrill	1909	25	cosmopolitan
Retiboletus	Manfr. Binder & Bresinsky	2002	5	north temperate regions
Rheubarbariboletus<ref name="Vizzini 2015"/>	Vizzini, Simonini & Gelardi	2015	2	Europe
Rhodactina	Pegler & T.W.K.Young	1989	2	India, Thailand
Rossbeevera<ref name="Lebel 2012"/>	T.Lebel & Orihara	2011	9	Asia, Australia
Royoungia	Castellano, Trappe & Malajczuk	1992	1	Australia
Rubroboletus<ref name="Zhao 2014"/>	Kuan Zhao & Zhu L.Yang	2014	8	Widespread
Rugiboletus<ref name="Wu 2015"/>	G. Wu & Zhu L. Yang	2015	2	East Asia
Setogyroporus	Heinem. & Rammeloo	1999	1	tropical Africa
Singerocomus<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	T.W.Henkel & M.E.Sm.	2016	3	??
Singeromyces	M.M.Moser	1966	1	Argentina
Sinoboletus	M.Zang	1992	10	China
Solioccasus<ref name="Trappe 2013"/>	Trappe, Osmundson, Manfr.Binder, Castellano & Halling	2013	1	Australasia
Spongiforma<ref name=Desjardin2009/>	Desjardin, Manf. Binder, Roekring & Flegel	2009	2	Thailand, Malaysia
Strobilomyces	Berk.	1851	Template:Sort	cosmopolitan
Suillellus	Murrill	1909	11	North America, Europe
Sutorius<ref name=Halling2012/>	Halling, Nuhn & Fechner	2012	3	North America, Costa Rica, Africa, S.E. Asia, Australia
Tubosaeta	E.Horak	1967	5	Africa, Asia
Tylopilus	P.Karst	1881	Template:Sort	widespread
Veloporphyrellus	L.D.Gómez & Singer	1984	1	Central America
Wakefieldia	Corner & Hawker	1952	2	Asia, Europe
Xanthoconium	Singer	1944	7	cosmopolitan
Xerocomellus<ref name="Šutara 2008"/>	Šutara	2008	24	North and South America, Europe
Xerocomus<ref name="Šutara 2008"/>	Quel	1887	>20	widespread
Zangia<ref name="Li 2011"/>	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

File:Weilangta Phylloporus sp.jpg

Phylloporus sp. Wielangta Forest, Tasmania

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.<ref name=Corner1972/> Over 100 species belonging to 52 genera have been reported from China, which has emerged as one of the worldwide hotspots of Boletaceae diversity.<ref name="Wu et al. 2016"/> The family is also reasonably well-represented in the Mediterranean region, where many rare or range-restricted species can be found.<ref name="Loizides 2019"/>

Ecology

As heterotrophic organisms, the majority Boletaceae species are symbiotic, and form mutually beneficial ectomycorrhizal associations with various trees and shrubs.<ref name="Aeger 2006"/><ref name="Tedersoo et al. 2010"/><ref name="Tedersoo et al. 2013"/> However, a number of ancestral species in genera Buchwaldoboletus and Pseudoboletus, are saprotrophic or parasitic.<ref name="Pilat 1969"/><ref name=Binder2006/><ref name="Tedersoo et al. 2010"/> Evidence suggests that some, if not all, species of Chalciporus might also have a mycoparasitic interaction with other fungi.<ref name="Tedersoo et al. 2010"/><ref name="Nuhn 2013"/> 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.<ref name=Singer1986/><ref name="Tedersoo et al. 2010"/>

Most frequently associated tree-hosts are members of the Fagaceae, particularly oak (Quercus), beech (Fagus) and chestnut (Castanea).<ref name="Alessio 1985"/><ref name="Munoz 2005"/><ref name="Galli 2007"/> 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).<ref name="Loizides 2019"/> Some boletes are also known to grow in association with Cistaceae shrubs, mainly Cistus<ref name=Coma06/> and Helianthemum,<ref name="Barden 2007"/> and at least one species (Leccinellum corsicum) is exclusively associated with rockrose.<ref name="Munoz 2005"/><ref name="Loizides 2016"/>

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,<ref name="Courtecuisse 1995"/><ref name="Munoz 2005"/> whereas the poisonous Rubroboletus satanas is predominantly calciphilous and mostly occurs on chalk.<ref name=Nilper/><ref name="Lannoy & Estadès 2001"/> Other species, such as Hemileccinum impolitum or Leccinellum lepidum, are indifferent to the substrate and frequently occur on both calcareous and acidic soil.<ref name="Loizides 2019"/>

Conservation

A number of Boletaceae species are considered rare, vulnerable or endangered, and some have been included in regional or national Red Lists. Rubroboletus dupainii is listed among the 33 threatened fungi of Europe, as part of Appendix I of the Bern Convention.<ref name="Dahlberg 2006"/> Rubroboletus rhodoxanthus is considered extinct in England<ref name="Kibby 2016"/> and critically endangered in the Czech Republic.<ref name="Mikšik 2012"/> Also critically endangered in the Czech Republic are Aureoboletus moravicus, Buchwaldoboletus sphaerocephalus, Butyriboletus fuscoroseus, Imperator rhodopurpureus, Leccinum roseotinctum and Rubroboletus rubrosanguineus.<ref name="Mikšik 2012"/> Eleven species of Boletaceae, Boletus aereus, Boletus pinophilus, Butyriboletus regius, Hemileccinum impolitum, Imperator luteocupreus, I. rhodopurpureus, I. torosus, Rubroboletus dupainii, R. lupinus, R. pulchrotinctus and R. satanas, are considered vulnerable or endangered in North Macedonia and have been included in the national Red List of fungi.<ref name="Karadelev & Rusevska 2013"/> Similarly, twenty species of Boletaceae are included in the Red List of fungi in Bulgaria.<ref name="Gyosheva et al. 2006"/>

Research from the Mediterranean region suggests that many boletes might be under threat from accelerated climate changes and long-term drought. In a ten-year study from the island of Cyprus, most bolete species were found to be rare, highly restricted by low soil moisture and exhibited very erratic fruiting patterns strongly correlating to annual, late summer and early autumn precipitation.<ref name="Loizides 2019"/>

Edibility

A large number of boletes are edible, few are delicious and some are considered to be true culinary delicacies. The much sought after king bolete (Boletus edulis), in particular, is a species of high commercial value and has been described as "the wild mushroom par excellence".<ref name=Carluccio2003/> In the Province of Parma in northern Italy, the four most sought after boletes, Boletus edulis, B. aereus, B. reticulatus and B. pinophilus, have been collected and commercially exploited for centuries.<ref name="Sitta 2008"/> Boletes are widely collected and sold in markets throughout Spain, particularly the province of Aragon.<ref name="De Roman 2004"/> Scandinavian cuisine praises boletes. Template:Citation needed They are a regular feature of Finnish cuisine and, especially the king bolete, is considered an unsurpassed culinary mushroom, widely used in various soups, sauces, casseroles and hotpots.Template:Citation needed Bolete mushrooms are sometimes also used as pizza topping, not unlike champignons, shiitake, or portobellos.

Two species of Butyriboletus, the royal bolete (B. regius) and the butter bolete (B. appendiculatus) are also culinary valued, though much less common than the ceps. In northern Europe, two of the commonest and most frequently collected edible boletes are the bay bolete (Imleria badia), whose pores bruise blue-green, and the orange birch bolete, which is a Leccinum with an orange cap and which bruises a bluish grey.Template:Citation needed

Several guidebooks recommend avoiding all red-pored boletes, but both Neoboletus luridiformis (= Neoboletus erythropus) and Suillellus luridus are edible when well-cooked and widely consumed in certain parts of Europe.

Lookalikes

Poisonous or otherwise inedible species are also present in the family, however, such as the unpalatable bitter species Caloboletus calopus and the aptly named bitter bolete (Tylopilus felleus), with a taste compared to bile, as well as some orange-capped species of Leccinum. As the bitter bolete resembles somewhat the king bolete, it can produce literally a bitter disappointment to the mushroom hunter. The rule of thumb is that the bitter bolete has pink pores, and a brownish stipe with a dark brown (sometimes approaching black) reticulum, while the cep has whitish pores, which in maturity become yellowish or sometimes with a faint olivaceous tint, a light-colored (white and/or similar in color to the rest of the stipe) reticulum and white hyphae tufts at the base of the stipe. The bitter bolete also lacks the stuffed or plugged pore appearance (caused by a hyphal mat of cheilocystidia) that is common in the cep and its allies. If uncertain, tasting a small piece of cap context should clinch the identification, since Tylopilus felleus has a strong, foul bitter taste.

Toxicity

File:Boletus satanas.JPG

Devil's bolete (Rubroboletus satanas)

Rubroboletus satanas has long been considered to be poisonous, though it is not known to have been responsible for any fatalities and the symptoms are predominantly gastrointestinal in nature. A glycoprotein, bolesatine, is thought to be responsible for the poisonings.<ref name="pmid1707561">Template:Cite journal</ref> When given to mice, Bolesatine causes massive thrombosis,<ref>Template:Cite journal</ref> while at lower concentrations it is a mitogen, inducing cell division to human T lymphocytes.<ref>Licastro F, Morini MC, Kretz O, Dirheimer G, Creppy EE; Stirpe F. (1993). "Mitogenic activity and immunological properties of bolesatine, a lectin isolated from the mushroom Boletus satanas Lenz". International Journal of Biochemistry. 25 (5): 789–792.</ref> A similar compound, bolevenine, has been isolated from the poisonous Neoboletus venenatus in Japan.<ref name=Matsuura2007/>

More recent studies have associated the poisoning caused by R. satanas with hyperprocalcitonemia,<ref>Merlet A, Dauchy FA, Dupon M. (2012). Hyperprocalcitonemia due to mushroom poisoning. Clin Infect Dis. 54: 307–308.</ref> and classified it as a distinct syndrome among fungal poisonings.<ref>Template:Cite journal</ref> Several other boletes are known to cause varying degrees of gastrointestinal symptoms, especially if eaten raw or insufficiently cooked.

One incident of death associated with Rubroboletus pulcherrimus was reported in 1994; a couple developed gastrointestinal symptoms after eating this fungus, with the husband finally succumbing. An autopsy revealed infarction of the midgut.<ref name=Benjamin1995/>

See also

• Bolete eater
• List of North American boletes

References

Cited texts

• Template:Cite book