Gymnopus ponderosae R.H. Petersen, 2016

Petersen, Ronald H. & Hughes, Karen W., 2016, Micromphale sect. Perforantia (Agaricales, Basidiomycetes); Expansion and phylogenetic placement, MycoKeys 18, pp. 1-122 : 67-75

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Gymnopus ponderosae R.H. Petersen

sp. nov.

7. Gymnopus ponderosae R.H. Petersen sp. nov.


United States, California, Humboldt Co., Rte 299, Grey’s Falls Campground, N40°54.422', W123°42.420', 16.XI.1996, coll RHP, TFB 9020 ( TENN-F-55669).


ponderosae = Latinized, referring to Pinus ponderosa , fruiting habitat of the species.


1) fruiting on dead needles of Pinus ponderosa ; 2) pileipellis with diverticulate hyphae and broom cell-like hyphal termini; 3) pileipellis broom cell-like hyphal termini and cheilocystidia arbuscular, with conspicuous stalk but hardly swollen distal portion; 4) rhizomorphs conspicuous, hairlike, curly, unbranched, -35 × 0.1-0.4 mm; 4) spores perhaps dimorphic.


Basidiomata (Figs 53 View Figure 53 , 54A View Figure 54 ) scattered on needle duff, usually solitary on individual needles, occasionally two per needle. Pileus 3-13 mm broad, applanate but with wide inflexed margin, occasionally slightly depressed, delicately tuberculate, not umbonate, subtly sulcate-striate, matt; disc brown ("Mars brown" 8F7, “bister” 5F8), grayish avellaneous to dull deep avellaneous; limb light brown ("sayal brown" 6 C5, "tawny olive" 5C5) to near "tilleul buff" 7B2. Lamellae adnexed to adnate, subdistant, not anastomosing, not pseudocollariate but seceding and appearing pseudocollariate after drying, subventricose, total lamellae (Fig. 54B View Figure 54 ) = 22-28, through lamellae = 13-15, (fresh) light brownish orange (6C4-3) to avellaneous, (dry) gray with hint of olive ("deep olive buff" 3C3, "light grayish olive" 30B2); lamellulae in one rank, rudimentary. Stipe 24-40(-60) × 0.5-0.8 mm broad, glabrous-shining over all, tapering gradually downward from mid-section to base, insititious, upward “avellaneous” (concolorous with lamellae, 7B3), socket at lamellar junction dark brown, downward black ("fuscous black" 6F4, "chaetura black" 2F3). Rhizomorphs (Fig. 54A View Figure 54 ) common, -35 × 0.1-0.4 mm, hair-like, black, glabrous-shining, kinked but not branched, attached to substrate with basal pad, sparse, not attached to basidiomata but closely associated. Odor negligible; taste negligible.

Habitat and phenology.

Fruiting on dead needles, twigs and debris of Pinus ponderosa (three-needle pine); distribution probably following distribution of Pinus ponderosa (at least California, Idaho, Washington); late autumn.

Pileipellis constructed of three elements involved in a minimal slime matrix over central areas: 1) hyphae 3-7 µm diam, firm- to thick-walled [wall 0.7-1 µm thick, subhyaline singly, pigmented dull yellow-olive brown in mass (PhC)], conspicuously clamped, strongly encrusted (Fig. 55A, B View Figure 55 ); crust material in thick scabs with profile calluses -1.5 µm thick or as annular ornamentation (Fig. 52B View Figure 52 ) or with profile calluses -1 µm thick or minute “flakes” adherent to a slime sheath; 2) free-form hyphae 4-6 µm diam, tibiiform to meandering, thin- to firm-walled (wall -1 µm thick, hyaline), often diverticulate with a combination of lobes and diverticula (Figs 55C,D View Figure 55 , 56A, B View Figure 56 ); diverticula -8 × 1-1.2 µm, digitate, often dichotomous, subrefringent; lobes -8 × 2-3 µm at base, fin-shaped (triangular), non-refringent; and 3) broom cell-like termini (Fig. 56C-F View Figure 56 ), arbuscular, stalked (stalk 4-13 × 3-5 µm), hardly or not inflated dis tally, branched in 1-2 ranks, beset with setulae 3-12 × 1-1.5 µm, digitate, often somewhat catenulate, often dichotomous, subrefringent, apparently free (not in slime). Pileus trama loosely interwoven; hyphae 2.5-6.5 µm diam, firm-walled, conspicuously clamped, weakly encrusted in “flakes.” Pleurocystidia (Fig. 57A-D View Figure 57 ) 24-37 × 7-9.5 µm, fusiform, conspicuously clamped; contents homogeneous, often with partitioned contents at apex. Basidioles clavate to ampulliform; basidia (Fig. 57E-H View Figure 57 ) (25-)32-38 × (7-)8-10 µm, clavate, often with slight constriction to produce capitulate morphology, clamped, 4-sterigmate; contents minutely heterogeneous. Basidiospores (Fig. 54C View Figure 54 ) possibly dimorphic: 1) (5-)5.5-7(-8.5) × (3-)3.5-5 µm (Q = 1.11-2.43; Qm = 1.67; Lm = 6.2 µm); 2) (6.5-)7-8.5 × 3.5-4.5 µm (Q = 1.75-2.43; Qm = 2.01; Lm = 7.7 µm), broadly ellipsoid to rotund-ellipsoid, pip-shaped, smooth, thin-walled, inamyloid; contents minutely granular. Cheilocystidia (Fig. 58 View Figure 58 ) 18-35 × 10-17 µm, broom cell-like, stalked [stalk (9-)15-27 × 4-5 µm, sometimes minutely roughened], without dilated distal portion, branched in 1-2 ranks, obscurely clamped; setulae -8 × 1-1.5 µm, often gnarled and/or branched, subrefringent (PhC). Stipe medullary hyphae 3-10 µm diam, hyaline, thick-walled (wall -2 µm thick), obscurely clamped, with minimal slime matrix, strictly parallel. Stipe cortical hyphae 4-10 µm diam, thick-walled [wall -2 µm thick, pigmented yellow brown (PhC)], obscurely clamped; surface hyphae encrusted in minute scabs, making surface cells appear rough. Caulocystidia not observed.


Collections accepted as four separate species ( G. " scoticus " nom. prov., G. " adventitius " nom. prov., G. pinophilus , G. ponderosae ) fruit on dead needles of Pinus spp. Of these, the former two are found in Gymnopus sect. Androsacei , while the latter two belong in sect. Perforantia . Both G. ponderosae and G. adventitius fruit on needles of Pinus ponderosae and superficially resemble one another. Both exhibit black, glabrous-shining stipes and dark brown pilei, but the pileipellis of G. ponderosae comprises repent, encrusted hyphae, diverticulate hyphae and broom cell-like hyphal termini, while G. adventitius pileipellis does not show diverticulate hyphae and broom cell-like hyphal termini. Moreover, stipes of G. adventitius often produces adventitious rhizomorphic structures from wounds, not seen in G. ponderosae .

The small clade comprising G. pinophilus and G. ponderosae is found sister to that of core sect. Perforantia . Pileipellis construction, which includes diverticulate hyphae and pileipellis "broom cells" is characteristic of a " Rameales structure," indicative of sect. Androsacei , but hardly that of traditional Perforantia , although involved in minimal slime. Marasmioid cheilocystidia also separate this pine-loving alliance from sect. Perforantia . Rhizomorphs, while not typically as long as basidiome stipe, are common, obvious and arise from the same needles as basidiomata.

TENN53488-TFB5627 (Idaho, G. ponderosae ) was the only representative of mating group III of " Marasmius androsaceus " by Gordon (1994) and Gordon and Petersen (1997). The taxonomic concept of the latter, however, was broad ([see Desjardin and Petersen (1989); Gilliam (1976)], including two separate taxa now known to be members of sect. Androsacei (as well as G. ponderosae in sect. Perforantia ), and perhaps other organisms for which haploid isolates were unavailable for pairing experiments.

The possibility of dimorphic spores is reported here also for G. pinophilus . Although reported for other mushroom groups (notably hygrophoroids) the cause of this phenomenon is not known in the group treated here. Basidia are uniformly 4-spored and basidia are conspicuously clamped, indicative of normal nuclear number and behavior.

Specimens examined.

United States, California, Humboldt Co., Rte 299, Grey's Falls Campground , N40°54.422', W123°42.420', 16.XI.1996, coll RHP (as Marasmius sp.), TFB 9020 ( TENN-F-55669; holotype) GoogleMaps . Idaho, Bonner Co., vic. Priest River, Priest River Experimental Forest , 25.IX.1992, coll RHP (as Marasmius sp.), TFB 5627 ( TENN-F-53488); same locale, same date, coll RHP (as Marasmius sp.), TFB 5633 ( TENN-F-52411); Valley Co. , vic. McCall , N44.911 W116.097, 16.IX.1977, coll. SD Libonati-Barnes (as Marasmius androsaceus ), SDLB 1461 ( WTU-F-9083) GoogleMaps . Washington, Pend Oreille Co., Roosevelt Grove , N48°45'15.89", W117°03'30.33", 29.VI.1993, coll L. Norvell (as Marasmius androsaceus ), LN93.06.29-16 ( WTU-F-8918) GoogleMaps .