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Leccinum chromapes (Frost) Singer, 1947

= Tylopilus chromapes (Frost) A.H. Sm. & Thiers (1968)
= Boletus chromapes Frost (1874)
? = Tylopilus cartagoensis Wolfe & Bougher (1993)

by Michael Kuo

Synopsis:

Here is a gorgeous bolete, easily recognized by its pinkish cap, its chrome yellow stem base, and the pink scabers on the surface of its stem. It is mycorrhizal--but unlike most species of Leccinum it appears to be "generalist," able to form mycorrhizae with a wide variety of trees, including both hardwoods and conifers. Leccinum chromapes is found in eastern North America, in Texas, and in Mexico--and a similar if not identical species is recorded from the oak forests of Central America. This mushroom has been shifted between Leccinum and Tylopilus so many times that one is tempted to call it "Leccilopilus chromapes"; see below for details. Leccinum chromapes is edible. I have not tried it.

Technical Description:

Ecology: Mycorrhizal with a wide variety of hardwoods and conifers (apparently a generalist; analysis of 229 collection records from online herbaria produced a long list of diverse trees without supporting any hypotheses regarding mycorrhizal limits), appearing in diverse ecosystems; often solitary, but also frequently growing scattered or gregariously; (June,) July, August, and September--and December on the Gulf Coast. My collections have been made under Populus grandidentata, Populus tremuloides, and Pinus resinosa in August and September.

Distribution: Apparently widely distributed east of the Great Plains; also found in Texas and recorded by amateur collectors in Mexico. Among the 229 collections found in online herbaria, only two were made outside of this range: a poorly documented collection from 1901 in California, and a Washington collection made by Smith (AHS 72375), both housed in MICH. These two records may represent data entry or identification errors, since Thiers (1975) did not include Leccinum or Tylopilus chromapes in his treatment of California boletes, and other West-Coast treatments (Arora, 1986; Scates, 2004; Wood & Stevens, 2006) either specify the taxon as eastern in distribution or do not include it. Figure 1 represents the distribution of Leccinum chromapes based on online herbarium collection locations, Metzler & Metzler (1992; Texas), and Both (1993; "Georgia"). My collections have been made in Emmet and Cheboygan counties, in Michigan.

Macromorphology: Pileus 3-11 cm; convex becoming broadly convex or nearly plane; surface dry or tacky, finely tomentose or nearly glabrous; occasionally somewhat pitted; when young pink to pale red, fading to pinkish tan, tan or ochraceous; without a sterile margin. Context whitish or faintly pinkish; often pinkish beneath the cuticle; unchanging when sliced and exposed to air, or rarely faintly bluish (Snell & Dick, Grund & Harrison) or yellowish in limited areas; quickly invaded in the stipe by larvae and frequently brown and cavernous in the lower portion at maturity. Tubes to 14 mm long; whitish, becoming pinkish and finally brownish; pore surface creamy white becoming pinkish, then brownish to reddish brown, not bruising, depressed at the stipe; 1-3 round to angular pores per mm. Stipe 4-17 cm long; 1-2.5 cm wide; at maturity more or less equal or tapering to apex, but with a pinched-off base; whitish to pinkish apically, chrome yellow basally (occasionally yellow overall); finely pruinose or subreticulate apically; densely scabrous except over the base; scabers pink to reddish brown; basal mycelium chrome yellow. Odor and taste not distinctive. Exsiccata ochraceous overall, retaining the yellow on the stem (even in the 1874 type collection, according to Halling [1983]) and becoming reddish brown in the tubes. Spore print pinkish brown to cinnamon brown or purplish brown.

Chemical reactions: Iron salts greenish to olive on context; KOH brownish on pileus surface and flesh; ammonia yellow on pileus surface.

Micromorphology: Basidiospores subfusoid; inamyloid; hyaline or yellowish in KOH; smooth; (8-) 11-17 x 4-6 µ. Basidia clavate; four-sterigmate (also two-sterigmate per Grund & Harrison); up to 36 x 14 µ. Hymenial cystidia fusoid-ventricose to fusoid; up to 50 x 12 µ or larger; often scarcely projecting beyond the basidia; hyaline in KOH; scattered. Pileipellis (Figure 2) a tangled layer of repent or suberect hyphae up to 7 µ wide; the terminal elements with rounded apices, not swollen; hyaline to yellow or golden yellow in KOH. Caulocystidia (Figure 2) scattered; in bundles with caulobasidia; variously shaped (subclavate, fusoid, cylindric, subcapitate, irregular); up to 48 x 15 µ; hyaline to yellowish in KOH.

Molecular Data: Two partial sequences have been deposited in GenBank: AY612834 (28S ribosomal RNA, deposited by T. Y. James et al. with a voucher of "RV98.107," which is presumably a Rytas Vilgalys collection in the Duke herbarium), aligned by Binder & Hibbet (2004) and by den Bakker & Noordeloos (2005); and AF139709 (28S large subunit ribosomal RNA, deposited by Binder & Besl without a voucher citation), aligned by Binder & Besl (2000), Binder & Hibbet (2004), and den Bakker & Noordeloos (2005). In the Binder & Hibbett alignment AF139709 is placed near Leccinum while AY612834 is sister to a clade containing Tylopilus rhoadsiae, Boletus gertrudiae, Boletus violaceofuscus, and Boletus separans. In the den Bakker & Noordeloos alignment, both AF139709 and AY612834 are sister to the remainder of Leccinum, and the authors conclude that the taxonomic position of Leccinum chromapes "is still doubtful," citing the contradictory Binder & Hibbett results (however, den Bakker & Noordeloos refer to the taxon as "Leccinum chromapes," and include it throughout their treatment in the Leccinum clade).

Comments:

Although recent molecular results (Binder & Hibbett, 2004; den Bakker & Noordeloos, 2005) suggest placement of this species in Leccinum, they are not entirely conclusive (see above); better support for the idea comes from Singer's contention (1947, 1986) that scabers in Leccinum need not darken to dark brown or black--an idea well supported by the European delineation of Leccinum albostipitatum (with white scabers that do not darken) and better molecular results (Binder & Hibbett, 2004; den Bakker & Noordeloos, 2005) nesting section Luteoscabra (including Leccinum longicurvipes and Leccinum subglabripes, with reddish to reddish brown scabers) within the Leccinum clade.

Several chromapes-like taxa have been described from outside North America. Leccinum cartagoensis (Wolfe & Bougher) Halling & Mueller, under oaks at high elevations in Costa Rica, has a pinkish gray to gray or nearly black cap, a grayish stem, and flesh that stains erratically pinkish; it shares the pink scabers and chrome yellow stipe base. Halling & Mueller (2003, 2007) note that Leccinum cartagoensis is generally smaller than Leccinum chromapes; they have given the provisional name of "subcartagoensis" to a black-capped form with darker scabers.

In Asia and in Australia, a wide variety of morphologically distinct taxa apparently belonging to the chromapes group have been described. Wolfe & Bougher (1993) describe 8 taxa (Tylopilus subchromapes, T. palumanus, T. queenslandianus, T. propriorichromapes, T. chlorinosmus, T. chromoreticulatus, T. pinophilus, and T. hongoi). At least one additional chromapes-like taxon, Tylopilus virens (W. F. Chiu) Hongo (illustrated), has been described from Asia; there may be others but I have not searched exhaustively for literature representing taxa outside North America. DNA from an undocumented "Tylopilus virens" specimen sequenced by Binder & Hibbet (2004) was placed near Leccinum with weak support. Wolfe & Bougher contend (without the support of molecular evidence) that the chromapes group

apparently originated in Laurasia. Populations of the subgenus migrated southwards from eastern Asia with their ectomycorrhizal hosts during Miocene/Pleistocene glaciations and subsequently adapted to different hosts in north-eastern Australia . . . Northern hemisphere populations disjuncted by the formation of the Atlantic Ocean are now recognised as new species in China . . . and in Japan. During Pleistocene glaciation North American populations may have diverged in North and Central America that are now recognised in Central America as T. cartagoensis and in North America as T. chromapes.

This is quite a lot to deduce from comparative morphological analysis, but fascinating nonetheless--and the authors have documented specific and diverse mycorrhizal associations ranging from Pinus to Accacia and Eucalyptus (among others) for seven of the eight taxa they describe (the eighth, Tylopilus chlorinosmus, is noted as associated with spruce-fir by Ron Petersen in collection records at TENN), basing their argument in large part on the biogeography of host trees. Since preliminary molecular results suggest the possibility that the chromapes group may be basal to the remainder of Leccinum, a DNA study focused on the worldwide taxa, accompanied by good ecological data, might provide essential information for an understanding of the genus.

Figure 1

Figure 2

Tylopilus chromapes, Japan

Tylopilus virens, Japan

Tylopilus virens, Japan

References and Material Studied:

Collections Examined: MICHIGAN: Kuo 09070101 (Emmet County), Kuo 09120400 (Cheboygan County). NEW YORK: A. S. Methven 4753 (Essex County; EIU). ILLINOIS: A. S. Methven 5791 (Clark County; EIU).

Collection Notes Examined: Bigelow 10473 (Maine, 1962; NYBG); Bigelow 16576 (Maine, 1971; NYBG).

Online Herbarium Records Examined: NY: 80; MICH: 110; OSU: 0; TENN: 2; BPI: 37.

Field Guides and Online Treatments: Cole, 1910; Graham, 1944; Miller, 1972; Smith, 1973; Glick, 1979; Smith, Smith & Weber, 1981; Arora, 1986; McKnight & McKnight, 1987; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; Halling, 2006; McNeil, 2006; Miller & Miller, 2006; Phillips, 2007.

Technical References: Atkinson, 1900; Coker & Beers, 1943; Singer, 1947; Smith & Thiers, 1968; Snell & Dick, 1970; Smith & Thiers, 1971; Halling, 1983; Both, 1993; Wolfe & Bougher, 1993; Halling & Mueller, 2003; Binder & Hibbett, 2004; den Bakker & Noordeloos, 2005; Ortiz-Santana et al., 2007. Full citations for these works can be found here.

Cite this page as:

Kuo, M. (2007, May). Leccinum chromapes. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/leccinum_chromapes.html

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