Boletus frostii
Encyclopedia
Boletus frostii, commonly
known as Frost's bolete or the apple bolete, is a bolete
mushroom first described scientifically in 1874. A member of the Boletaceae
family, the mushrooms produced by the fungus have tubes and pores instead of gills on the underside of its cap
. The fruit bodies
may be recognized by their dark red sticky caps, the red pores, the network-like pattern of the stem
, and the bluing reaction to tissue injury. Another characteristic of young, moist fruit bodies are the amber
drops exuded on the pore surface.
Boletus frostii is a mycorrhiza
l species, and the fruit bodies are typically found growing near hardwood
trees, especially oak
. Boletus frostii is distributed in the eastern United States from Maine
to Georgia
, Mexico, and Costa Rica. A subspecies
, Boletus frostii ssp. floridanus, has been described and differs from the typical species in the color of the fruit body, and texture of the cap. Boletus frostii mushrooms are edible
, but generally not recommended because of the risk of confusion with other poisonous red-pored boletes.
, based on specimens found in Brattleboro, Vermont
. He named the fungus after his friend, another amateur American mycologist, Charles Christopher Frost
, who published a description of the species in his 1874 survey of the bolete
s of New England
. When the name of a species is contributed by an individual, but the name is formally published by another, the contributor's name can be cited, separated from the publishing author as apud. An example of this includes writings by American mycologist Rolf Singer
, who in 1947 referred to the species as Boletus Frostii Russell apud Frost. Bernard Ogilvie Dodge
made reference to this species in 1950 in his address to the Mycological Society of America
, when he spoke about the role of the amateur mycologist in discovering new species:
specimen, mycologist Roy Halling examined both the original material and the accompanying notes, and concluded that it was Frost who made the original species determinations, and further suggested "there is no evidence to show that Russell ever collected B. frostii or wrote a description of it." William Murrill
in 1909 placed the species in the genus Suillellus, while Sanshi Imai transferred it to Tubiporus in 1968; both of these genera have since been folded into Boletus. The mushroom is commonly known
as "Frost's bolete", or the "apple bolete". In Mexico, its vernacular name is panza agria, which translates to "sour belly".
of the young fruit body
ranges from a half sphere to convex, later becoming broadly convex to flat to shallowly depressed, with a diameter of 5 –. The edge of the cap is curved inwards, although as it ages it can uncurl and turn upwards. Under moist conditions, the cap surface is sticky as a result of having a cuticle
that is made of gelatinized hypha
e. If the fruit body has dried out after a rain, the cap is especially shiny, sometimes appearing finely areolate (having a pattern of block-like areas similar to cracked dried mud). Young specimens have a whitish bloom on the cap surface.The color is bright red initially, but fades with age. The flesh
is up to 2.5 cm (0.984251968503937 in) thick, and ranges in color from pallid to pale yellow to lemon-yellow. The flesh has a variable staining reaction in response to bruising, so some specimens may turn deep blue almost immediately, while others turn blue weakly and slowly.
The tubes comprising the pore surface (the hymenium
) are 9–15 mm deep, yellow to olivaceous yellow (mustard yellow), turning dingy blue when bruised. The pores are small (2 to 3 per mm) and circular, and until old age a deep red color that eventually becomes paler. The pore surface is often beaded with yellowish droplets when young (a distinguishing characteristic), and readily stains blue when bruised. The stem
is 4 to 12 cm (1.6 to 4.7 in) long, and 1 to 2.5 cm (0.393700787401575 to 0.984251968503937 in) thick at its apex. It is roughly equal in thickness throughout its length, or it may taper somewhat toward the top, though some specimens may appear ventricose (swollen in the middle). The stem surface is mostly red, or yellowish near the base; it is reticulate—characterized by ridges arranged in the form of a net-like pattern. Mycelia, visible at the base of the stem, is yellowish-white to light yellow.
The spore print
of B. frostii is olive-brown. The spores
are thick-walled, smooth, and spindle-shaped, with dimensions of 11–15 by 4–5 µm
. Larger spores up to 18 µm long may also be present. The cap cuticle, or pileipellis
, is made of a tangled layer of gelatinized hypha
e that are 3–6 µm wide. The spore-bearing cells, the basidia, are four-spored and measure 26–35 by 10.5–11.5 µm. Cystidia are non-fertile cells interspersed among the basidia, and they are prevalent in the hymenial tissue of B. frostii. These hyaline
(translucent) cells can range in shape from somewhat like a spindle (tapering at each end, but with one end typically rounded), to subampullaceous—shaped somewhat like a swollen bottle; they are 30–53 long by 7.5–14 µm wide.
, and David Arora
mentions that it is commonly sold in farmers' markets in Mexico; a 1997 study suggests that it is only consumed in rural areas in Querétaro
state. Its taste and odor have been described as "pleasant" and somewhat like citrus
, although the cuticle of the cap may taste acidic.
Chemical analysis
of fresh fruit bodies collected in Mexico showed them to have the following composition: moisture
94.53%; ash
3.23 milligrams per gram of mushroom (mg/g); dietary fiber
30.24 mg/g; fat
3.68 mg/g; and protein 15.81 mg/g. The free fatty acid content of dried fruit bodies was 45 mg/g, slightly more than the common button mushroom, which had 35 mg/g. The majority of this total was oleic acid
(19.5 mg/g), linoleic acid
(16.8 mg/g), and palmitic acid
(16.9 mg/g).
he found in Florida
during his 1942–3 tenure of a Guggenheim Memorial Fellowship. Boletus frostii ssp. floridanus differs from the typical form in the lighter color of the cap and in texture of the cap surface: the subspecies is tomentose
(covered with dense, short, soft, matted hairs) or velutinous (like velvet), compared to the relatively smooth surface of the typical. Singer notes that although the physical characteristics between the two taxa may be blurred and are hard to define, the area of origin is a reliable indicator of subspecies status. Subspecies floridanus is found on shaded lawns and scrubland in open oak stands in non-tropical regions of Florida, typically on grassy or sandy soil. It grows under or near several oak species, including chapman oak (Quercus chapmanii), swamp laurel oak (Q. laurifolia), and southern live oak
(Q. virginiana), and it fruits between May and October.
s in eastern North America and southern Arizona
. Often confused with B. frostii is B. permagnificus, but the latter species is known only known from France and Italy, and always grows in association with oaks. The fruit bodies of young specimens of B. kermesinus, newly described from Japan in 2011, are similar in appearance to B. frostii. In addition to its distribution, B. kermesinus can be distinguished from B. frostii by having flesh that does not bruise blue, and a stem in which the reticulum is not as deep and coarse. B. pseudofrostii, found in Belize
, produces smaller caps that are 1.7 to 2 cm (0.669291338582677 to 0.78740157480315 in) in diameter.
nutrients from the soil and channels these into the plant, while the plant provides the fungus with sugars, a product of photosynthesis
. The characteristic feature of the mycorrhiza is the presence of a sheath of fungal tissue that encases the terminal, nutrient-absorbing rootlets of the host plant. The fungus forms an extensive underground network of hypha
e that radiate outwards from the surface of the root sheath, effectively increasing the surface area for nutrient absorption. The hyphae also invade between the root cortical cells
to form a Hartig net
. Using pure culture
techniques, Boletus frostii has been shown to form mycorrhizae with Virginia pine
(Pinus virginiana, while a field study confirms the same association with the oak Quercus laurina.
The fruit bodies grow solitary, scattered, or in groups on the ground under hardwood trees; the fungus fruits in summer to early autumn. William Murrill
noted its preference for growing in "thin oak woods, where the light is sufficient to enable grass to grow", and Alexander H. Smith
mentioned its preference for growing in "thin, sandy soil under scrub oak." In the United States, it is distributed from Maine
south to Georgia
, extending west to Tennessee
, Michigan
, and southern Arizona
. In Mexico, it is often found under Madrone. It has also been collected in Costa Rica
, where it associates with the oak species Quercus copeyensis
, Q. costaricensis
, Q. rapurahuensis
, and Q. seemanii. A 1980 publication tentatively suggested that the fungus was also present in Italy, but the author later determined that the putative B. frostii was actually Boletus siculus.
Fruit bodies can be parasitized by the mold-like fungus Sepedonium ampullosporum. Infection results in necrosis
of the mushroom tissue, and a yellow color caused by the formation of large amounts of pigmented aleurioconidia (single cell conidia produced by extrusion from the conidiophores).
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
known as Frost's bolete or the apple bolete, is a bolete
Boletus
Boletus is a genus of mushroom, comprising over 100 species. The genus Boletus was originally broadly defined and described by Elias Magnus Fries in 1821, essentially containing all fungi with pores...
mushroom first described scientifically in 1874. A member of the Boletaceae
Boletaceae
Boletaceae are a family of mushrooms, primarily characterized by developing their spores in small pores on the underside of the mushroom, instead of gills, as are found in agarics. Nearly as widely distributed as agarics, they include the Cep or King Bolete , much sought after by mushroom hunters...
family, the mushrooms produced by the fungus have tubes and pores instead of gills on the underside of its cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
. The fruit bodies
Basidiocarp
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 not produce such structures...
may be recognized by their dark red sticky caps, the red pores, the network-like pattern of the stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
, and the bluing reaction to tissue injury. Another characteristic of young, moist fruit bodies are the amber
Amber (color)
Amber is an orange-yellow color that got its name from the material known as amber. Due to this, amber can refer not to one but to a series of shades of orange, since the natural material varies from nearly yellow when newer to orange or reddish-orange when older.-Amber:Amber is a pure chroma color...
drops exuded on the pore surface.
Boletus frostii is a mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
l species, and the fruit bodies are typically found growing near hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
trees, especially oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
. Boletus frostii is distributed in the eastern United States from Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
to Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, Mexico, and Costa Rica. A subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, Boletus frostii ssp. floridanus, has been described and differs from the typical species in the color of the fruit body, and texture of the cap. Boletus frostii mushrooms are edible
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
, but generally not recommended because of the risk of confusion with other poisonous red-pored boletes.
Taxonomy
This species was named by the Unitarian minister John Lewis Russell of Salem, MassachusettsSalem, Massachusetts
Salem is a city in Essex County, Massachusetts, United States. The population was 40,407 at the 2000 census. It and Lawrence are the county seats of Essex County...
, based on specimens found in Brattleboro, Vermont
Brattleboro, Vermont
Brattleboro, originally Brattleborough, is a town in Windham County, Vermont, United States, located in the southeast corner of the state, along the state line with New Hampshire. The population was 12,046 at the 2010 census...
. He named the fungus after his friend, another amateur American mycologist, Charles Christopher Frost
Charles Christopher Frost
Charles Christopher Frost was an American botanist. He described several species of fungi from the New England area of the United States. In one paper, Frost described 22 new species of boletes, and he was later credited with the discovery of three additional species. His personal herbarium of...
, who published a description of the species in his 1874 survey of the bolete
Bolete
A bolete is a type of fungal fruiting body characterized by the presence of a pileus that is clearly differentiated from the stipe, with a spongy surface of pores on the underside of the pileus...
s of New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
. When the name of a species is contributed by an individual, but the name is formally published by another, the contributor's name can be cited, separated from the publishing author as apud. An example of this includes writings by American mycologist Rolf Singer
Rolf Singer
Rolf Singer was a German-born mycologist and one of the most important taxonomists of gilled mushrooms in the 20th century....
, who in 1947 referred to the species as Boletus Frostii Russell apud Frost. Bernard Ogilvie Dodge
Bernard Ogilvie Dodge
Bernard Ogilvie Dodge was an American botanist and pioneer researcher on heredity in fungi. Dodge was the author of over 150 papers dealing with the life histories, cytology, morphology, pathology and genetics of fungi, and with insects and other animal pests of plants...
made reference to this species in 1950 in his address to the Mycological Society of America
Mycological Society of America
The Mycological Society of America is a learned society that serves as the professional organization of mycologists in the U.S. and Canada. It was founded in 1932...
, when he spoke about the role of the amateur mycologist in discovering new species:
They would have informed us all about the man Russell, who named a fine new bolete for his friend Frost, and about the man Frost, who names a fine new bolete for his friend Russell. Boletus Frostii and Boletus Russelli are mushrooms with character, even though they were described by amateurs.However, in attempting to establish a lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
specimen, mycologist Roy Halling examined both the original material and the accompanying notes, and concluded that it was Frost who made the original species determinations, and further suggested "there is no evidence to show that Russell ever collected B. frostii or wrote a description of it." William Murrill
William Murrill
William Alphonso Murrill was an American mycologist, known for his contributions to the knowledge of the Agaricales and Polyporaceae.- Education :...
in 1909 placed the species in the genus Suillellus, while Sanshi Imai transferred it to Tubiporus in 1968; both of these genera have since been folded into Boletus. The mushroom is commonly known
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
as "Frost's bolete", or the "apple bolete". In Mexico, its vernacular name is panza agria, which translates to "sour belly".
Description
The shape of the capPileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
of the young fruit body
Basidiocarp
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 not produce such structures...
ranges from a half sphere to convex, later becoming broadly convex to flat to shallowly depressed, with a diameter of 5 –. The edge of the cap is curved inwards, although as it ages it can uncurl and turn upwards. Under moist conditions, the cap surface is sticky as a result of having a cuticle
Pileipellis
thumb|300px||right|The cuticle of some mushrooms, such as [[Russula mustelina]] shown here, can be peeled from the cap, and may be useful as an identification feature....
that is made of gelatinized hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e. If the fruit body has dried out after a rain, the cap is especially shiny, sometimes appearing finely areolate (having a pattern of block-like areas similar to cracked dried mud). Young specimens have a whitish bloom on the cap surface.The color is bright red initially, but fades with age. The flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
is up to 2.5 cm (0.984251968503937 in) thick, and ranges in color from pallid to pale yellow to lemon-yellow. The flesh has a variable staining reaction in response to bruising, so some specimens may turn deep blue almost immediately, while others turn blue weakly and slowly.
The tubes comprising the pore surface (the hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...
) are 9–15 mm deep, yellow to olivaceous yellow (mustard yellow), turning dingy blue when bruised. The pores are small (2 to 3 per mm) and circular, and until old age a deep red color that eventually becomes paler. The pore surface is often beaded with yellowish droplets when young (a distinguishing characteristic), and readily stains blue when bruised. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
is 4 to 12 cm (1.6 to 4.7 in) long, and 1 to 2.5 cm (0.393700787401575 to 0.984251968503937 in) thick at its apex. It is roughly equal in thickness throughout its length, or it may taper somewhat toward the top, though some specimens may appear ventricose (swollen in the middle). The stem surface is mostly red, or yellowish near the base; it is reticulate—characterized by ridges arranged in the form of a net-like pattern. Mycelia, visible at the base of the stem, is yellowish-white to light yellow.
The spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
of B. frostii is olive-brown. The spores
Basidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In grills under a cap of one common species in the phylum of...
are thick-walled, smooth, and spindle-shaped, with dimensions of 11–15 by 4–5 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
. Larger spores up to 18 µm long may also be present. The cap cuticle, or pileipellis
Pileipellis
thumb|300px||right|The cuticle of some mushrooms, such as [[Russula mustelina]] shown here, can be peeled from the cap, and may be useful as an identification feature....
, is made of a tangled layer of gelatinized hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e that are 3–6 µm wide. The spore-bearing cells, the basidia, are four-spored and measure 26–35 by 10.5–11.5 µm. Cystidia are non-fertile cells interspersed among the basidia, and they are prevalent in the hymenial tissue of B. frostii. These hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
(translucent) cells can range in shape from somewhat like a spindle (tapering at each end, but with one end typically rounded), to subampullaceous—shaped somewhat like a swollen bottle; they are 30–53 long by 7.5–14 µm wide.
Edibility and nutritional composition
In 1910, Murrill wrote of this mushroom's edibility: "Usually viewed with suspicion because of its red hymenium, but its properties are not accurately known." Since then, several authors have advised against consuming the species, due to its resemblance to other toxic red-capped boletes. Despite this, Boletus frostii is edibleEdible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
, and David Arora
David Arora
David Arora is an American mycologist, naturalist, and writer. He is the author of two popular books on mushroom identification, Mushrooms Demystified and All That the Rain Promises and More.......
mentions that it is commonly sold in farmers' markets in Mexico; a 1997 study suggests that it is only consumed in rural areas in Querétaro
Querétaro
Querétaro officially Estado Libre y Soberano de Querétaro de Arteaga is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 18 municipalities and its capital city is Santiago de Querétaro....
state. Its taste and odor have been described as "pleasant" and somewhat like citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
, although the cuticle of the cap may taste acidic.
Chemical analysis
Food chemistry
Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. The biological substances include such items as meat, poultry, lettuce, beer, and milk as examples...
of fresh fruit bodies collected in Mexico showed them to have the following composition: moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
94.53%; ash
Ash (analytical chemistry)
In analytical chemistry, ashing is the process of mineralization for preconcentration of trace substances prior to chemical analysis. Ash is the name given to all non-aqueous residue that remains after a sample is burned, and consist mostly of metal oxides....
3.23 milligrams per gram of mushroom (mg/g); dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...
30.24 mg/g; fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
3.68 mg/g; and protein 15.81 mg/g. The free fatty acid content of dried fruit bodies was 45 mg/g, slightly more than the common button mushroom, which had 35 mg/g. The majority of this total was oleic acid
Oleic acid
Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. It has the formula CH37CH=CH7COOH. It is an odorless, colourless oil, although commercial samples may be yellowish. The trans isomer of oleic acid is called elaidic acid...
(19.5 mg/g), linoleic acid
Linoleic acid
Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...
(16.8 mg/g), and palmitic acid
Palmitic acid
Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated fatty acids found in animals and plants. Its molecular formula is CH314CO2H. As its name indicates, it is a major component of the oil from palm trees . Palmitate is a term for the salts and esters of...
(16.9 mg/g).
Subspecies
In 1945, Rolf Singer reported a subspeciesSubspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
he found in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
during his 1942–3 tenure of a Guggenheim Memorial Fellowship. Boletus frostii ssp. floridanus differs from the typical form in the lighter color of the cap and in texture of the cap surface: the subspecies is tomentose
Tomentose
Tomentose is a term used to describe plant hairs that are flattened and matted, forming a woolly coating known as tomentum. Often the hairs are silver or gray-colored...
(covered with dense, short, soft, matted hairs) or velutinous (like velvet), compared to the relatively smooth surface of the typical. Singer notes that although the physical characteristics between the two taxa may be blurred and are hard to define, the area of origin is a reliable indicator of subspecies status. Subspecies floridanus is found on shaded lawns and scrubland in open oak stands in non-tropical regions of Florida, typically on grassy or sandy soil. It grows under or near several oak species, including chapman oak (Quercus chapmanii), swamp laurel oak (Q. laurifolia), and southern live oak
Southern live oak
Quercus virginiana, also known as the southern live oak, is a normally evergreen oak tree native to the southeastern United States. Though many other species are loosely called live oak, the southern live oak is particularly iconic of the Old South....
(Q. virginiana), and it fruits between May and October.
Similar species
Other red-capped boletes include the poisonous B. flammans and B. rubeoflammeus; the former grows most commonly under conifers, the latter in association with hardwoodHardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
s in eastern North America and southern Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. Often confused with B. frostii is B. permagnificus, but the latter species is known only known from France and Italy, and always grows in association with oaks. The fruit bodies of young specimens of B. kermesinus, newly described from Japan in 2011, are similar in appearance to B. frostii. In addition to its distribution, B. kermesinus can be distinguished from B. frostii by having flesh that does not bruise blue, and a stem in which the reticulum is not as deep and coarse. B. pseudofrostii, found in Belize
Belize
Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...
, produces smaller caps that are 1.7 to 2 cm (0.669291338582677 to 0.78740157480315 in) in diameter.
Habitat, distribution, and ecology
Boletus frostii is a mycorrizhal species, meaning that the fungus forms associations with the roots of various species of trees. This association is mutualistic, because the fungus absorbs mineralDietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
nutrients from the soil and channels these into the plant, while the plant provides the fungus with sugars, a product of photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. The characteristic feature of the mycorrhiza is the presence of a sheath of fungal tissue that encases the terminal, nutrient-absorbing rootlets of the host plant. The fungus forms an extensive underground network of hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e that radiate outwards from the surface of the root sheath, effectively increasing the surface area for nutrient absorption. The hyphae also invade between the root cortical cells
Cortex (botany)
In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells...
to form a Hartig net
Hartig net
Hartig net is a hyphal network, that extends into the root, penetrating between epidermal and cortical cells. This network is a site of nutrient exchange between the fungus and the host plant...
. Using pure culture
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
techniques, Boletus frostii has been shown to form mycorrhizae with Virginia pine
Virginia Pine
Pinus virginiana is a medium-sized tree, often found on poorer soils from Long Island in southern New York south through the Appalachian Mountains to western Tennessee and Alabama. The usual size range for this pine is 9–18 m, but can grow taller under optimum conditions. The trunk can be...
(Pinus virginiana, while a field study confirms the same association with the oak Quercus laurina.
The fruit bodies grow solitary, scattered, or in groups on the ground under hardwood trees; the fungus fruits in summer to early autumn. William Murrill
William Murrill
William Alphonso Murrill was an American mycologist, known for his contributions to the knowledge of the Agaricales and Polyporaceae.- Education :...
noted its preference for growing in "thin oak woods, where the light is sufficient to enable grass to grow", and Alexander H. Smith
Alexander H. Smith
Alexander Hanchett Smith was an American mycologist known for his extensive contributions to the taxonomy and phylogeny of the higher fungi, especially the agarics.-Early life:...
mentioned its preference for growing in "thin, sandy soil under scrub oak." In the United States, it is distributed from Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
south to Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, extending west to Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
, Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
, and southern Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. In Mexico, it is often found under Madrone. It has also been collected in Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
, where it associates with the oak species Quercus copeyensis
Quercus copeyensis
Quercus copeyensis is a species of oak endemic to the Talamancan montane forests of Costa Rica and Panama. It is often found with Quercus costaricensis in the upper montane forests, to elevation.-External links:*...
, Q. costaricensis
Quercus costaricensis
Quercus costaricensis is a species of oak endemic to the Talamancan montane forests of Costa Rica and Panama. It is often found with Quercus copeyensis in the upper montane forests, to 3100 meters elevation.-External links:*IUCN Red List: *...
, Q. rapurahuensis
Quercus rapurahuensis
Quercus rapurahuensis, the Talamanca Oak, is a tropical species of oak in the red oak group . It is native to Costa Rica and northern Panama in tropical premontane and montane forests.-Source:...
, and Q. seemanii. A 1980 publication tentatively suggested that the fungus was also present in Italy, but the author later determined that the putative B. frostii was actually Boletus siculus.
Fruit bodies can be parasitized by the mold-like fungus Sepedonium ampullosporum. Infection results in necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
of the mushroom tissue, and a yellow color caused by the formation of large amounts of pigmented aleurioconidia (single cell conidia produced by extrusion from the conidiophores).
External links
- Mushroom Observer Photographs