Tetrapyrgos nigripes (Fr.) E. Horak, Sydowia

Honan, Amy H., Desjardin, Dennis E., Perry, Brian A., Horak, Egon & Baroni, Timothy J., 2015, Towards a better understanding of Tetrapyrgos (Basidiomycota, Agaricales): new species, type studies, and phylogenetic inferences, Phytotaxa 231 (2), pp. 101-132 : 110-111

Tetrapyrgos nigripes (Fr.) E. Horak, Sydowia 39: 102. 1987 [1986]. Fig. 3a–f

Basionym: Marasmius nigripes Fr., Epicr. Syst. Mycol. (Upsaliae) : 383. 1838 [1836–1838].

Replaced synonym: Agaricus nigripes Schwein., Schr. Naturf. Ges. Leipzig 1: 678. 1822, nom. illegit. (non Agaricus nigripes Bull., Herb. Fr. 8: tab. 344. 1788.).

Synonyms: Chamaeceras nigripes (Fr.) Kuntze, Revis. Gen. Pl. (Leipzig) 3(2): 456. 1898. Heliomyces nigripes (Fr.) Morgan, J. Mycol. 12: 93. 1906. Marasmiellus nigripes (Fr.) Singer, Pap. Mich. Acad. Sci. 32: 130. 1946, (publ. 1948). Pterospora nigripes (Fr.) E. Horak, Sydowia 36: 133. 1983. Marasmius caesius Murrill, Bull. Torrey Bot. Club 67: 148. 1940.

Holotype: Not extant. Type locality: USA, North Carolina.

Description based on newly collected specimens: Pileus 4–18 mm diam., convex and sometimes with incurved to inrolled margin when young, becoming convex, broadly convex to plano-convex or plano-depressed, with straight to upturned margin, rarely with a small papilla or umbo, sometimes shallowly umbilicate, at first even overall, soon rugulose-striate or sulcate-striate to the disc; surface dull, dry, opaque, glabrous to minutely pruinose, white overall, discoloring irregularly or at disc in age with grey spots or splotches. Context very thin (<0.5 mm), watery white. Lamellae adnate to subdecurrent, close to subdistant, with 1–3 series of lamellulae, not or becoming forked and intervenose in age, 0.5–1.75 mm broad, pure white or staining grey irregularly in age, edges occasionally minutely scalloped. Stipe 5–30 × 0.3–2 mm, central to eccentric, terete, rarely cleft and compressed, with equal or flared apex, gradually tapering downward, tough, pliant, hollow, subinsititious from a flattened circular pad of grey appressed mycelium; surface dull, dry, white pruinose or granulose overall; apex pure white; base becoming dark grey (7–8F2) to nearly black or bluish black. Odor and taste not distinctive.

Basidiospores (6.0–) 7.2–11.2 × 5.6–9.6 μm [x mr = 6.8–9.5 × 6.0–8.0 μm, x mm = 8.5 ± 0.9 × 7.3 ± 0.7 μm, Q = 1.0–1.6, Q mr = 1.1–1.2, Q mm = 1.2 ± 0.03, n = 20, s = 7], tetrahedral, hyaline, inamyloid, thin-walled. Basidia clavate, 4-spored, hyaline, inamyloid, thin-walled. Basidioles 20–37 × 3–8 μm, clavate, hyaline, inamyloid, thin-walled. Pleurocystidia absent. Cheilocystidia 23–44 × 2.8–6.4 μm; apex bulbous and smooth, often branched, elsewhere diverticulate, hyaline, inamyloid, thin-walled; diverticula 0.8–8.5 × 0.8–3.5 μm, cylindrical or knob-like, occasionally branched. Pileipellis a Rameales -structure of loosely interwoven diverticulate hyphae 2–9 μm diam, with a nearly trichodermium layer of erect terminal cells 15–38.5 × 2–8 μm, occasionally cells branched with diverticulate apex, most often cells with a smooth, bulbous apex that is often branched, hyaline, inamyloid, thin-walled; diverticula 0.8–7.2 × 0.8–4.8 μm, cylindrical to knob-like, occasionally branched. Lamellar trama interwoven; hyphae cylindrical, smooth. Stipe tissue monomitic; hyphae 2.4–8 μm diam, parallel, cylindrical, tightly packed, inamyloid, thin-walled; cortical hyphae yellowish brown; medullary hyphae hyaline. Caulocystidia 34–48 × 4–8 μm diam., usually with a smooth, bulbous apex, occasionally branched, elsewhere diverticulate, hyaline, inamyloid, thin-walled; diverticula 0.4–4 × 0.4–3.2 μm, cylindrical or knob-like, occasionally branched. Clamp connections present.

Habitat and known distribution: Gregarious on leaves and twigs of Quercus spp . ( Fagaceae ) and various dicotyledonous plants. Eastern Canada, eastern United States.

Material examined:— UNITED STATES. Florida: Alachua County, Rochelle Hammock, 8 miles east of Gainesville , 24 July 1958, HD Thiers 4786 ( SFSU) ; New York: Essex County, Pettigrew Brook, TJ Baroni 6020 ( CORT) ; North Carolina: Swain Co., vicinity Bryson City, Great Smoky Mountains National Park ( GSMNP), end of Indian Creek Road, N35˚30 ’06”, W83˚24 ’03”, 8 August 2004, coll. by K. W. Hughes, TFB 12137 ( TENN 60065 ) ; Ohio: Lorain, Co., 8 miles West of Oberlin, Green St. , Girl Scout Camp , 11 September 1989, DE Desjardin 4958 ( SFSU) ; Tennessee: Blount Co., GSMNP, Parsons Branch Rd. near Cades Cove, 31 July 1991, DE Desjardin 5326 ( SFSU) ; Knox Co., S of Knoxville, Cherokee Dr., University of Tennessee Woodlot, 15 September 1987, DE Desjardin 4519 ( SFSU) ; Knox Co., Knoxville, University of Tennessee, near old library, 7 July 1991, DE Desjardin 5136 ( SFSU) ; Sevier Co, GSMNP, Roaring Fork trail area, 9 July 1987, DE Desjardin 4347 ( SFSU) .

Commentary: Tetrapyrgos nigripes was described originally from North Carolina ( USA) and is recognized by a white pruinose pileus that may discolor grey in spots, diverticulate cystidial elements with bulbous apex, and a black or blue-black stipe covered with pruinae and arising from a dark basal disc. This species, the first agaric ever to be described with tetrahedral basidiospores, is rather common on hardwood leaves and twigs in eastern North America. Redhead (1989) reported numerous specimens from eastern Canada (Ontario, Quebec) and eastern United States (District of Columbia, Florida, Illinois, Indiana, Iowa, Louisiana, Massachusetts, Michigan, Minnesota, Missouri, New York, North Carolina, Pennsylvania, Tennessee, Texas, Vermont, Virginia, Wisconsin). Marasmius caesius , described from Florida, is herein accepted as a synonym of T. nigripes (see type studies below).

Tetrapyrgos nigripes differs from T. longicystidiata in having shorter cheilocystidia and in lacking a pileus disc that is consistently grey to olivaceous grey. Specimens from Mexico and Colombia reported as T. nigripes by Redhead (1989) may represent T. longicystidiata . Specimens from the Old World reported in the literature as Marasmiellus nigripes ( Pegler 1986, Corner 1996) probably represent T. subcinerea .

A specimen from the British Virgin Islands [ Tortola Island: below entrance of Sage Mountain National Park, 6 Oct, 2001, DJ Lodge 20, TOR-89 (SFSU)] and one from Hawaii [Kauai, along road up to Kokee, elev. 914 m, 24 November 1990, G Wong 888 (SFSU)] are morphologically indistinguishable from T. nigripes but have ITS sequences that vary by 2–3% from topotypical material of T. nigripes . Tentatively recognized as T. aff. nigripes , together with T. nigripes they form a grade basal to other Tetrapyrgos species ( Fig. 1 ). Additional material from the Caribbean region and the Hawaiian Islands, and sequences of additional genes may help determine whether they represent distinct species.

Figures

FIGURE 1. Maximum likelihood (-lnL = 3590.75887) topology of Tetrapyrgos specimens sampled as part of this investigation based on ITS sequence data. Numbers separated by “/” represent non-parametric maximum likelihood bootstrap (BS) proportions and Bayesian posterior probablilites (PP), respectively. Branches highlighted in bold received combined support values of ≥70%/0.95.

FIGURE 3. Macroscopic and anatomical features for Tetrapyrgos nigripes (DED 5326). a. Basidiomes. b. Basidiospores. c. Basidium and basidioles. d. Cheilocystidia. e. Pileipellis terminal cells. f. Caulocystidia. Scale bars: a = 10 mm, b–f = 10 μm. Illustrated by D.E. Desjardin.