Tricholoma felschii Ovrebo, Hughes & Halling, 2019

Ovrebo, Clark L., Hughes, Karen W. & Halling, Roy E., 2019, Three new species of Tricholoma from Costa Rica, Phytotaxa 392 (1), pp. 33-44 : 34-38

Tricholoma felschii Ovrebo, Hughes & Halling sp. nov. ( Figs. 1 , 3 , 6 )

Mycobank no.:—MB 827631

Diagnosis:—Characterized by medium sized basidiomes, gray pileus, and presence of a pileal ixocutis, pseudoparenchymatous pileal subcutis and cheilocystidia. Differs from similar gray species by micromorphology and ITS sequences.

Holotype:— COSTA RICA. San Jose Prov.: Jardín de Dota, 3.5 km W of Interamerican Highway at Empalme, 9˚42’52” N, 83˚58’28” W, 2220 m, 7 June 1997, A.- G. Felsch 21 ( USJ 66016 ; Isotype NY).

Etymology:—Named in honor of A. -G. Felsch who collected and studied Tricholomas in Costa Rica.

Description:— Pileus 30–65 mm wide, convex when young, often with low umbo, expanding to plane and usually with a low, rounded umbo, occasionally rimose; surface moist, dull, with long radiating innate fibrils, smooth or rugulose, dark gray to dark dull smoky gray overall (10YR 4/1–2) or dark olivaceous brownish gray (6E2–3) especially when older, sometimes a little lighter near edge, occasionally with dark gray streaks; context 2–7 mm thick, light buff to light gray, odor and taste strongly farinaceous. Lamellae 3–8 mm wide, deeply sinuate to adnexed, off-white, or some pale grayish, occasionally dark grayish marginate in places, dingy yellowish buff when older, entire, close; lamellulae in numerous tiers. Stipe 25–100(120) mm long, 5–10 mm thick, equal, base rounded or sub-bulbous; surface silky fibrillose with occasional loose fibrils projecting, off-white to grayish white, dirty buff at base where handled; solid, context off-white. Macrochemical color reaction: —no reaction with 3% KOH.

Basidiospores 6–7.5(8) × (4.5)5–5.5 μm (mean=7.06 × 4.95, Q=1.33–1.56, mean Q=1.43), elliptical in profile and face views, smooth, thin-walled, colourless, inamyloid. Basidia 28–36 × 7–12 μm, 4-sterigmate, clavate, colourless. Cheilocystidia present but not necessarily projecting much above hymenium, 20–40 × 6–16 μm, broadly clavate, sphaeropedunculate or fusiform, often collapsed, colourless to light brown. Pleurocystidia absent. Lamellar trama composed of parallel colourless hyphae, 5–14 μm wide. Subhymenium composed of colourless hyphae, 3–4 μm wide. Pileipellis as an ixocutis, hyphae radially arranged or interwoven in a gelatinous matrix, 4–8 μm wide, smooth, thin-walled or occasionally roughed with incrustations, colourless, dull yellow to translucent refractive grayish yellow or yellowish brown. Subcutis made up of pseudoparenchymatous hyphae, cells 8–25 μm wide, broadly elliptic to slightly inflated, colourless but light to dark brown as a layer, some with brown plaque-like incrustations. Pileitrama made up of colourless hyphae 5–15 μm diam. Stipitipellis composed of smooth, thin-walled colourless hyphae 3–5 μm wide. Stipititrama composed of colourless hyphae 4–12 μm wide. Clamp connections absent.

Habitat:—Scattered on soil, mixed hardwoods/conifers in the United States; in Costa Rica beneath Quercus copeyensis and Q. seemannii .

Additional collections studied:— USA: Arkansas: Baxter Co.: Leatherwood Wilderness, Ozark-St. Francis National Forests, exact site unknown, approximate coordinates for center of Wilderness are 36° 05.5’ N, 92° 23’ W, 23 October 2013, coll. Alfredo Justo, Ovrebo 5177 (CSU). Tennessee: Sevier Co.: Great Smoky Mountains National Park: Greenbrier Trail to Whaley Cemetery, 35°42’27.2” N, 83°22’54.1” W, 21 October 2005, C. L. Ovrebo 4562 (CSU, TENN). Costa Rica: San Jose Prov.: Jardín de Dota, 3.5 km W of Interamerican Highway at Empalme, 9˚42’52” N, 83˚58’28” W, 2220 m, 15 June 1997, Ovrebo 3548 (USJ 109187) & Ovrebo 3549 (USJ 109188).

Discussion:— Tricholoma felschii is characterized by the gray pileus and medium-sized basidiomata. It has the strong farinaceous odor and taste, cheilocystidia, pseudoparenchymatous subcutis, and rugulose pileus that are shared with other species in the complex. The most similar Tricholoma species include T. marquettense and T. mutabile , both of which share the gray coloration with T. felschii . Tricholoma mutabile was described from California and has a gray to dark gray pileus with vinaceous or violaceous tones and discolors pink or orange at the stipe base ( Shanks 1996). Tricholoma marquettense was described from the upper peninsula of Michigan and has a medium gray pileus with a white margin and often is whitish over large areas ( Ovrebo 1986); however, the first author now has collections from Texas and Alabama. The two species can be distinguished from T. felschii by ITS sequences as well. Tricholoma griseoviolaceum Shanks (1996: 497) from California has a grayish violet pileus, cheilocystidia and a farinaceous odor and taste, but the pileus is not rugulose and it lacks a pseudoparenchymatous subcutis. Tricholoma atratum described in this paper from Costa Rica has a darker gray pileus, larger stature, larger spores and lacks cheilocystidia.

The T. felschii collections for which we have ITS sequences form a well-supported clade with three closely related entities, one from Costa Rica ( Fig. 1 , T. felschii clade a), one that appears to have a southeastern US distribution ( Fig. 1 , T. felschii clade b) and one that appears to have a more northern US / Canada extending into the Great Smoky Mountains National Park in Tennessee ( Fig. 1 , T. felschii clade c) based on available ITS sequences. Tricholoma felschii appears to be in the process of speciation based on ITS sequences but macromorphology is the same although there is a slight difference in spore dimensions (Ovrebo 5177 from Arkansas has the smallest spores, mean 6.55 x 4.73 μm). Tricholoma felschii clade a differs from clades b and c by a 13bp indel. Thus clades a, b and c may be considered subspecies or geographical variants.

Figures

FIGURE 1. PhyML analysis of the nuclear ribosomal ITS region. Collection locations where known are given by the US Postal code for states. GSM=Great Smoky Mountains NationalPark,Tennessee side; BC=Canada British Columbia; CR=Costa Rica; ENV=environmental sequence. Ecto=ectomycorrhizal root tip. Bootstrap values are given to the left of the supported node. Percent divergence calculations were calculated using all base pair differences (i.e., a 13bp insertion in CLO3549 and AGF21 was counted as 13 bp differences, not a single difference).

FIGURE 3. Basidiomes. Tricholoma felschii, Ovrebo 4562. Photo by C. L. Ovrebo. Scale line = 20 mm.

FIGURE 6. Microscopic features of Tricholoma species. Tricholoma felschii, holotype, A. basidiospores, B. cheilocystidia. Tricholoma costaricense, holotype, C. basidiospores, D. cheilocystidia. Scale line=10 μm. Drawings by C. L. Ovrebo.