Gymnopus menehune Desjardin, Halling et Hemmes, sp. nov.
Pileus 8-30 (-45) mm latus, late convexus vel plano-convexus, umbilicatus, translucens striatus vel ruguloso-striatus, hygrophanous, glaber, initio castaneus vel brunneus, dein pallide brunneus vel pallide brunneo-aurantiacus. Lamellae adnatae vel subdecurrentes, confertae vel densae, angustatae, albae vel pallide aurantio-albidae. Stipes 15-60 X 1-3 mm, centralis, terete vel compressus, aequalis, pruinosus vel pubescens, pallide brunneo-griseus, basi brunneus vel atrobrunneus; rhizomorphis albidus vel pallide aurantio-albidus. Odore raphanoideae. Basidiosporae 7.5-9.5 X 3.5-4.2 µm, subfusoideae, leves, hyalinae, inamyloideae, acyanophilae. Basidia 19-24 X 6-7 µm, 4-spora. Cheilocystidia numerosae, 22-42 X 6.5-10.0 µm, subcylindracea vel late clavata, 1-4 lobateae, hyalinae, tenuitunicatae. Pleurocystidia nulla. Hyphae pileipellis 2.5-5.5 µm latae, cylindraceae, diverticulae sparsis, pallide ochraceo-brunneus incrustatae. Caulocystidia 16-64 X 3-5 µm, irregulariter cylindraceae vel sinuosae. Fibulae praesentes. Dispersus vel subcaespitosus ad folia dejecta et detritum Casuarinae. HOLOTYPUS: Hawai`i, MacKenzie Beach State Park, 3 Aug. 1993, D. E.Desjardin 5866 (SFSU; ISOTYPUS: BISH, NY).
Pileus (Figs. 5, 6, 24) 8-30 (-45) mm diam, when young broadly convex to plano convex and often slightly umbilicate, expanding at maturity to campanulate or plane, umbilicate; margin decurved but soon becoming straight to uplifted and wavy, pellucid-striate to rugulo-striate; surface dull, moist to dry, hygrophanous, glabrous; reddish brown (8D7-8), dark brown (7E-F7 8) or brown (6-7E6-8) overall when young and moist or with a slightly paler margin, fading in age and with moisture loss to paler reddish brown (8D5-6), light brown (7D5-6; "hazel"), pale brownish grey (6C3) or pale brownish orange (5C4-5; "clay color"), and becoming beige to dingy tan when dried in situ. Context very thin (< 1 mm), watery concolorous with the surface, or white to buff. Lamellae ascending, adnate to subdecurrent, rarely shallowly adnexed, close to crowded with 4-6 series of lamellulae, narrow (1-2 mm), dingy buff to pale orange white (5A2) when young, remaining so in age or becoming pale greyish orange (5B3) or pale greyish brown (6C3); edges minutely pruinose, concolorous with the sides. Stipe 15-60 X 1-3 mm, central, terete or compressed and sometimes once-cleft, apex often flared, ±equal below or seldom gradually narrowed downward, pliant, tough, hollow; surface dull, dry, apex pruinose, base pubescent to tomentose; vestiture buff to pale orange white (5A2); ground color ranging from dingy buff to pale brownish grey (6C3) overall when young, hysterochroic, with base becoming brown (6-7E4-8) to dark brown (6-7F5-8) in age. Rhizomorphs copious, coarse, branched, white to pale orange white. Odor strong, like rancid radishes; taste somewhat sour, astringent.
Basidiospores (Fig. 25) (7.0-) 7.5-9.5 X 3.5-4.2 µm [range of means = 8.1--8.7 X 3.7--3.9 µm, mean of means = 8.3 ± 0.35 X 3.8 ± 0.1 µm, Q = 1.8-2.6, range of Q means = 2.1-2.4, mean of Q means = 2.2 ± 0.14, n = 15-20 spores per 8 specimens], elongate-ellipsoid to subfusoid, inequilateral in profile, smooth, hyaline, inamyloid, acyanophilic, white to pale cream in deposit. Basidia (Fig. 26) 19-24 (-27) X 6-7 µm with sterigmata up to 4.5 µm long, 4-spored, clavate. Basidioles (Fig. 26) fusoid to subacerose. Pleurocystidia absent. Cheilocystidia (Fig. 27) abundant (lamellar edge sterile), (16- ) 22-42 X (3.8--) 6.5-10.0 µm, subcylindrical, clavate, broadly clavate or irregular in outline, sometimes lobed (1-4 times), sometimes two-celled, hyaline, thin-walled, non-refractive. Pileipellis (Fig. 28) a cutis; hyphae 2.5-5.5 µm diam, slightly interwoven, radially arranged, cylindrical, non-inflated, with scattered cylindrical to clavate or sinuous outgrowths or branchlets and a few diverticula, not a Ramealis-structure; walls thin, non-gelatinous, incrusted with pale yellowish brown to brown pigments, inamyloid; terminal cells ranging from irregularly cylindrical to contorted or lobed, sometimes with knobby diverticula, hyaline to pale yellow, non-incrusted. Pileus trama interwoven; hyphae 3-8 µm diam, cylindrical, smooth or weakly incrusted, non gelatinous, hyaline, inamyloid, with moderately thick walls. Hymenophoral trama regular; hyphae 2.5-6.5 µm diam, cylindrical to contorted, otherwise like pileus tramal hyphae; subhymenium ramose. Stipe tissue monomitic; cortical hyphae 2.5-5 µm diam, parallel, cylindrical, non gelatinous, non-incrusted, hyaline to pale greyish brown, inamyloid, giving rise to erect caulocystidia; medullary hyphae 5--8 µm diam, like cortical hyphae. Caulocystidia (Fig. 29) 16- 64 (-88) X 3-5 (-7) µm, irregularly cylindrical to sinuous, obtuse, seldom apically lobed, thin walled, hyaline, inamyloid. No tissues turn green in 3% KOH. Clamp connections abundant in all tissues.
Habit, habitat and distribution. Scattered to subcespitose, in small clusters and often in "fairy rings" in duff under Casuarina equisetifolia in Coastal Casuarina Forest or in soil and leaf mulch in mixed Lowland Alien Forest, or in dense subcespitose clusters on wood chips in horticultural areas. June to February. Hawai`i, Maui.
Specimens Examined. U.S.A. HAWAII: Hawai`i, Hilo, American Savings parking lot, 5 Jul. 1996, DEH 1148; same location, 11 Jul. 1996, DEH 1169; same location, 6 Aug. 1996, DEH 1194; same location, 19 Aug. 1996, DED 6515 (NY, SFSU); same location, 17 Sep. 1996, DEH 1245; same location, 5 Nov. 1996, DEH 1296; Hawai`i, Hilo, Bayfront area, 17 Sep. 1996, DEH 1246; Hawai`i, Hilo, Mountain View area, Mike Au's Farm, 7 Nov. 1996, DEH 1302; Hawai`i, Hilo, 333 Kalili St., 19 Jul. 1993, DEH 239; same location, 2 Aug. 1993, DED 5862; Hawai`i, Hilo, Univ. of Hawai`i Campus, 29 Jun. 1994, DEH 485; Hawai`i, Hilo, Panaewa Zoo, N19°ree;39.273', W155°ree;04.341', 4 Jul. 1992, DEH 7.4.92.1; Hawai`i, Lava Tree State Park, N19°ree;29.0', W154°ree;54.5', 4 Jan. 1996, DED 6334; Hawai`i, MacKenzie Beach State Park, N19°ree;26.32', W154°ree;51.768', 3 Aug. 1993, DED 5866 (HOLOTYPE: SFSU; ISOTYPE: BISH, NY); same location, 28 Sep. 1993, DEH 270; same location, 19 Feb. 1994, DEH 421; same location, 4 Jan. 1996, DED 6339; same location, 25 Jun. 1996, DEH 1119; same location, 19 Aug. 1996, DED 6517; same location, 7 Nov. 1996, DEH 1303. Maui, Iao Valley State Park, N20°ree;52.975', W156°ree;32.700', 16 Jan. 1992, DED 5519.
Etymology. menehune: legendary race of small people who worked at night, i.e., Hawaiian fairies; referring to the common habit of the species growing in large `menehune' rings.
Commentary. Gymnopus menehune is characterized by the production of small, subcespitose basidiomes with brown, pellucid-striate, umbilicate pilei, crowded, narrow, pale orange white to pale greyish brown lamellae, a pubescent to tomentose, buff to brown stipe, elongate-ellipsoid basidiospores ( mean of means = 8.3 X 3.8 µm), voluminous and sometimes lobed cheilocystidia, and irregularly cylindrical to sinuous, thin-walled and hyaline caulocystidia. Pileipellis and basidiospore anatomy suggest placement in sect. Vestipedes subsect. Vestipedes (see Antonín & Noordeloos 1997: 23). Phenetically similar taxa include Gymnopus subcyathiformis (Murrill) Desjardin, Halling et Hemmes, comb. nov. [Basionym: Marasmius subcyathiformis Murrill, N. Amer. Flora 9: 269. 1915; ∫ Collybia subcyathiformis (Murrill) Pegler, Kew Bull. Add. Ser. 6: 139-1977; Holotype: Mexico, Colima, 3-4 Jan. 1910, leg. W. A. & E. L. Murrill no. 615 (NY!)], and Gymnopus collybioides (Speg.) Desjardin, Halling et Hemmes, comb. nov. [Basionym: Clitocybe collybioides Speg., Bol. Acad. Nac. Ci. 11(4): 387. 1889; ∫ Collybia collybioides (Speg.) Singer, Lilloa 23: 162. 1950; Holotype: Brasil, Apiahy, Apr. 1888, leg. Puiggari no. 2893 (LPS!)]. Gymnopus subcyathiformis differs from G. menehune in lacking abundant cheilocystidia and in lacking diverticulate branches on the pileipellis hyphae. Gymnopus collybioides differs in forming a subpruinose (not pubescent to tomentose) stipe, and a pileus with white central umbilicus that contrasts sharply with the rest of the pileus.
There occur two subtly different forms of G. menehune on the island of Hawai`i. One form develops basidiomes with deeply umbilicate, convex pilei that become plane only at maturity, produce a white spore deposit, and sporulate in large subcespitose clusters of 10-25 basidiomes on wood chips in horticultural areas. A second form develops basidiomes with shallowly umbilicate pilei that are initially plano-convex and soon become plane-undulate, produce a pale cream spore deposit, and sporulate singly or in small clusters of 2-8 basidiomes in large menehune rings in duff in Coastal Casuarina Forests or Lowland Alien Forests. The micromorphology of these two forms is indistinguishable. We do not consider these differences taxonomically significant. The single known population on the island of Maui (DED 5519), however, differs slightly in forming shorter basidiospores (6-7 µm long). Until more material from Maui is discovered for an analysis of variation, we cannot assess the taxonomic significance of these data.
Gymnopus menehune is found only in association with alien plants and is considered by us an introduced species. We are aware of at least one other Gymnopus species that occurs in the Hawaiian Islands. This undetermined taxon collected on leaves of crepe ginger [Costus speciosus (J. König) Sm.] in Lowland Alien Forest is allied with members of sect. Vestipedes and has elongate-clavate pileocystidia and cheilocystidia. Unfortunately, no basidiospores were observed on the two basidiomes that comprise the single collection [Maui, Koolau State Forest Reserve, Kolea Trail off Hana Hwy at 10 mi marker, 16 Jan. 1996, DED 6447 (SFSU)].
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