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Page number:324 
Remarks (internal):Gymnopus fuscotramus is characterized by a brown-incarnate colors in pileus and lamellae, sulcate pileus, free and distant lamellae, floccosesquamulose, mostly black stipe, well-developed black rhizomorphs, growing only on woody substrate (not arising from rhizomorphs), non-hymeniform pileipellis (cutis with diverticulate hyphae), abundant clamp connections, diverticulate to coralloid cheilocystidia, moderately thick-walled caulocystidia with obtuse apex, dextrinoid hyphae in cortex of stipe, and gray-brown pileal and hymenophoral trama.
Among other species in the section Androsacei with clamp connections, black rhizomorphs, non-glabrous stipe, and colored pileus and lamellae (not white or cream), Marasmius bactrosporus Singer, M. campinaranae Singer, and Setulipes brevistipitatus Antonín have (among others) much smaller basidiomata and more elongated spores. M. nigroimplicatus has thinner (?0.2 mm) and minutely pubescent rhizomorphs, adnate lamellae sometimes attached to a pseudocollarium, more elongated spores, and caulocystidia with thicker walls (1.8-5 µm). M. rigidichorda Petch has basidiomata arising also from the rhizomorphs, adnate lamellae, white context, hyaline hymenophoral trama, and caulocystidia with pointed apex. M. subrigidichorda has basidiomata arising also from the rhizomorphs, lamellae attached to a pseudocollarium, longer and wider rhizomorphs (?410 x 0.9 mm), hyaline hymenophoral trama, and caulocystidia with thicker walls (2-5 µm). M. thiersii Desjardin has crowded, adnate to adnexed lamellae, rare or absent rhizomorphs, and lacks cheilocystidia. Setulipes rhizomorphicola Antonín has much shorter (?3 mm) and eccentric stipe arising from rhizomorphs, adnate lamellae, and longer spores.
According to morphological characters, Gymnopus fuscotramus belongs to section Androsacei. However, our phylogenetic analysis using only ITS rDNA sequences do not place our taxon on the same clade with the two sequenced species from that section, G. androsaceus (L.) J.L. Mata & R.H. Petersen and G. quercophilus (Pouzar) Antonín & Noordel. However, G. fuscotramus is placed close to G. peronatus (Bolton) Gray (sect. Vestipedes). To further clarify phylogenetic relationships between G. fuscotramus and other Gymnopus species (especially from sect. Androsacei), more species (reliably identified) and more DNA sequences should be included in analyses. Our gymnopoid clade also includes Marasmiellus and Rhodocollybia species, which is in accordance with results of Moncalvo et al. (2002), Mata et al. (2004) and Wilson & Desjardin (2005). All these results indicate that Gymnopus and Marasmiellus (as conceived recently) are polyphyletic and that new taxonomic concepts inferred from DNA sequences should be proposed. However, since past phylogenetic analysis included only a small number of species from these two genera, further taxonomic solutions should be based on more extensive phylogenetic research with more species and DNA sequences included.
 
Description type:Original description 
Description:Gymnopus fuscotramus Meši?, Tkal?ec & Chun Y. Deng, sp. nov. Figs 1-7
MycoBank MB 519324
Pileus 12-21 mm broad, campanulate, sometimes with applanate or slightly depressed center, sulcate almost to the center, weakly translucently striate when moist, hygrophanous, brownish incarnate to incarnate-brown when moist (from 10B4 to 11D5), pale incarnate on drying, with darker, mostly dark red-brown to blackish-brown center, surface dull, dry. Lamellae free (without a collarium or pseudocollarium), distant (L = ca. 12, l = 1), ?2 mm broad, ventricose, reaching the margin of the pileus or almost so, sometimes slightly intervenose, brownish incarnate, with entire, concolorous edge. Stipe 15-30 x 1-1.5 mm, subcylindrical, orange- to red-brown in the upper part, downward brown-black to black, entirely pale brown floccose-squamulose, dry, hollow, insititious, arising directly from substrate (not from rhizomorphs). Context grayish-brown and very thin in pileus, whitish in stipe medulla, concolorous with surface in stipe cortex. Smell and taste not recorded. Rhizomorphs abundant, filiform, unbranched, ?135 mm long and ?0.5 mm thick, glabrous, black, with black to black brown inner context, hollow, apex with white globule or tapering and concolorous.
Spores [50/2/1] (6.7-)6.8-8.2-9.6(-9.8) x (3.0-)3.0-3.7-4.4(-4.8) µm, SD = 0.71 x 0.34, Q = 1.73-2.23-2.70, oblong to subcylindrical, in side view often amygdaliform or even lacrymoid, smooth, hyaline, thin-walled, non-amyloid, non-dextrinoid. Basidia 23-36 x 4.5-6 µm, narrowly clavate, (2)4-spored, thin-walled, hyaline, clamped. Basidioles narrowly clavate, cylindrical or fusoid. Lamellar edge sterile, composed of repent, diverticulate, hyaline to gray-brown, 1.5-8 µm broad hyphae, with clusters of cheilocystidia. Cheilocystidia 20-60 x 5-15(-25) µm, subcylindrical to irregularly clavate with irregular finger- to knob-like projections or coralloid, thin- to moderately thick-walled (?0.8 µm thick), hyaline to pale gray-brown. Pleurocystidia absent. Hymenophoral trama irregular, composed of 1-6(-8) µm broad, thin- to moderately thick-walled (?1 µm thick), subhyaline to pale gray-brown (gray-brown in mass) hyphae, pigment intracellular. Pileipellis a subregular cutis composed of 1.5-10 µm broad, mostly thin-walled, less frequently moderately thick-walled (?0.8 µm thick), subhyaline to brown, mostly diverticulate hyphae, with occasional coralloid elements, dark brown pigment often coarsely encrusted. Pileal trama composed of pale gray-brown (graybrown in mass), non-gelatinized, thin- to moderately thick-walled (?0.8 µm thick), 1-7 µm broad hyphae, pigment intracellular. Stipitipellis a cutis of parallel, 1.8-7 µm broad, brown hyphae with intracellular, sometimes also encrusted pigment. Caulocystidia very abundant, 5-100 x 4-12 µm, mostly cylindrical, subcylindrical or narrowly clavate, with obtuse apex, sometimes diverticulate, moderately thick-walled to thick-walled [walls 0.5-2(-2.5) µm thick], sometimes with one septa, often in groups, subhyaline to brown, with intracellular, sometimes also encrusted pigment. Stipe trama composed of parallel, thin- to thick-walled (?1.2 µm thick), 2-10 µm broad hyphae, hyaline in stipe medulla. Clamp connections present and abundant in all tissues. Chemical reactions: all parts of basidioma non-amyloid and non-dextrinoid except hyphae in cortical layer of stipe and caulocystidia, which are dextrinoid (red-brown in Melzer's reagent).
Habitat - In small clusters on a twig, in humid subtropical forest of Fagus longipetiolata and Castanopsis lamontii.
Distribution - Known only from the type locality in China.
 
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