|Major Groups > Boletes > Leccinum > Leccinum holopus|
Leccinum holopus (Rostkovius) Watling, 1960
= Leccinum holopus var. americanum Smith & Thiers, 1971
by Michael Kuo
Leccinum holopus is easily recognized by its association with birch in wet, boggy areas, and its whitish (or occasionally pale brownish) cap. In most collections the flesh in the base of the stem blues slightly when sliced, and in many collections the mature cap demonstrates greenish to bluish hues, especially near the margin. The scabers are initially whitish, but usually darken to brown or blackish. In many collections the flesh stains pinkish (and eventually grayish) when sliced--but this feature is variable, and in other collections the flesh does not change. Under the microscope it features a pileipellis disposed as a cutis, and long-necked caulocystidia that are hyaline to yellowish in KOH.
Ecology: Mycorrhizal with birch; often appearing in the outer zones of bog-fill ecosystems; growing alone or gregariously in (June) July, August, September, and October. Analysis of 126 collection records from online herbaria demonstrates overwhelming support for the birch-bog hypothesis. Collections that document tree associations either list birch or list trees that are often found growing with birch; collections that are silent on tree associations often list bogs or swamps, or are made in locations named for such ecosystems ("Reese's Bog," for example)--or come from locations in northern Michigan with which I am familiar, and which feature birch, especially in the outer zones of bogs.
Distribution: Apparently distributed throughout the range of Betula papyrifera in North America. Figure 1 represents the states and provinces for the 126 Leccinum holopus records in MICH, TENN, BPI, NY, and EIU, as well as the range of Betula papyrifera.
Macromorphology: Pileus 3-12 cm; convex becoming broadly convex or nearly plane; usually tacky, often becoming viscid with age; very finely tomentose (especially when young) or glabrous; whitish to yellowish or brown, sometimes developing greenish to bluish hues with age, especially near the margin--and/or developing pinkish hues over the disc; with a tiny (.5-1 mm) sterile margin but without substantial overhanging flaps. Context whitish, not changing or changing to pinkish or reddish (eventually grayish) when sliced and exposed to air; often bluish in the base of the stipe. Tubes to 2.5 cm long; whitish, becoming brownish to pinkish; pore surface whitish, becoming pinkish to brownish, often bruising yellowish to brown, depressed at the stipe; 1-2 pores per mm. Stipe 6-14 cm long; 10-23 mm wide; equal or subclavate; whitish; scabrous with whitish scabers that usually darken to brown, grayish, or blackish; sometimes bluing near the base. Odor and taste not distinctive. Exsiccata with a dirty whitish to pale tan or brownish pileus surface, a brown pore surface, and a pale yellowish brown stipe surface adorned with light brown scabers. Spore print cinnamon brown to brownish.
Chemical reactions: KOH negative on pileus surface or with a "pink flash lasting less than a second, then negative" (Grund & Harrison); negative to brownish on context. Ammonia pinkish on pileus surface; negative on context. Iron salts negative on pileus surface; negative to slightly olive on context.
Micromorphology: Basidiospores fusoid to subfusoid; inamyloid; yellowish in KOH; smooth; (13) 15-18 (21) x (4) 5-7 µ. Basidia clavate; four-sterigmate; up to 35 x 12.5 µ. Hymenial cystidia (Figure 2) lageniform to fusoid-ventricose or fusiform; up to 45 x 12 µ; hyaline in KOH. Pileipellis (Figure 2) a cutis of intertwined cylindric elements 3.5-7 µ wide; hyaline to grayish-ochraceous or brownish in KOH; terminal elements with rounded or subacute apices, not substantially swollen. Caulocystidia (Figure 2) in bundles with caulobasidia; variously shaped but mostly cylindric, fusoid-ventricose, or fusoid; often with a long, twisted neck; up to 70 x 14 µ or longer; hyaline to ochraceous or brownish in KOH.
Molecular Data: 22 partial sequences have been deposited in GenBank with the label Leccinum holopus. 12 of these sequences represent collections from various locations deposited by den Bakker and collaborators in preparation of an unpublished manuscript with the working title "Phylogeographic patterns in Leccinum sect. Scabra and the status of the arctic/alpine species L. rotundifoliae." The remaining 10 deposits represent sequences that have been aligned in Binder & Besl (2000), den Bakker and collaborators (2004a, 2004b, 2005), and Binder & Hibbett (2004).
I suspect that many herbarium collections labeled "Leccinum albellum" are actually Leccinum holopus, and vice-versa. The species are easily separated on the basis of their ecology (dry oak woods versus wet birch woods), but this fact has been subordinated to putative morphological differences in North American literature, making identification more difficult than it needed to be.
Smith & Thiers (1971) described Leccinum holopus var. americanum as differing from the typical variety in its pink-staining flesh, but the contemporary concept of Leccinum holopus (den Bakker & Noordeloos, 2005) allows the possibility of pink staining in the typical variety; I am treating var. americanum as a synonym.
References and Material Studied:
Collections Examined: MICHIGAN: Kuo 09120402 (Emmet County). WISCONSIN: A. S. Methven 8267 (1997, Lincoln County; EIU).
Online Herbarium Records Examined: NY: 6; MICH: 99; OSU: 0; TENN: 5; BPI: 16.
Field Guides and Online Treatments: Smith, Smith & Weber, 1981; Breitenbach & Kränzlin, 1991; Phillips, 1991/2005; Barron, 1999; Bessette, Roody & Bessette, 2000; McNeil, 2006; den Bakker & Noordeloos, 2007; Kuo, 2007; Phillips, 2007.
Technical References: Smith, Thiers & Watling, 1967; Snell & Dick, 1970; Smith & Thiers, 1971; Grund & Harrison, 1976; Both, 1993; Lannoy & Estades, 1995; Binder & Hibbett, 2004; den Bakker and collaborators (2004a, 2004b); den Bakker & Noordeloos, 2005. Full citations for these works can be found here.
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Cite this page as:
Kuo, M. (2007, April). Leccinum holopus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/leccinum_holopus.html