Albomagister leucoloma Matheny, Sanchez-Garcia & Vellinga 2024, sp. nov.

Albomagister leucoloma Matheny, Sánchez-García & Vellinga, sp. nov. (Figs. 3B, 6D–F) MYCOBANK: MB851400. TYPE: USA, Tennessee, Cocke County, Great Smoky Mountains National Park, Cosby, Maddron Bald Trail (35.7652 -83.2680), on soil and needle leaf litter in acidic cove hardwood forest under Tsuga canadensis, 10 October 2010, E.C. Vellinga ECV4202 (holotype designated here, TENN-F-065323). DIAGNOSIS: Basidiomes with an inocyboid habit, white with underlying grayish drab ground color, in age with straw yellow to amber-yellow discolorations on the pileus and stipe, on acidic soil in a cove hardwood forest under Tsuga canadensis. Phylogenetically distinct and sister to the clade including A. subaustralis and A. luteifolius. Habit small, inocyboid. Pileus 10–23 mm wide, obtusely conical, expanding with age, slightly umbonate and subcampanulate, margin decurved; surface dry but with some adhering soil particles, dull, innately white silky fibrillose, fibrils thinning at the center and revealing a grayish drab ground color, thicker and whitish or indistinctly straw yellow or grayish drab in places towards the margin; conext thick, odor, and taste not remarkable. Lamellae sinuate, moderately close, thick, broad, whitish to pale grayish white, becoming buff or tinged cream with age, edges white and indistinctly fimbriate. Stipe 15–25 × 2–5 mm, terete, equal; dry, fibrillose white, in age revealing amber yellow discolored areas, base covered with soil and needle litter of Tsuga canadensis. Basidiospores 5– 6.0 –7 × (3.5–)4– 4.3 –5 µm, Q 1.16– 1.40 –1.68 (n = 21/1), broadly elliptic to subovate, smooth, thin-walled, with a distinct apiculus, inamyloid and nondextrinoid. Basidia 29–40 × 6–7 µm, 4- spored, slenderly clavate, hyaline, thin-walled. Pleurocystidia 48–60(–86) × 14–16 µm, ventricose with a long slender pedicel, smooth, walls slightly thickened (ca. 1.0 µm thick), hyaline. Cheilocystidia 22–55 × 6–17 µm, many shorter than the pleurocystidia and thin-walled, also subfusiform, utriform, or clavate, some ventricose and long-pedicellate like the pleurocystidia, frequent on the lamellar edges but mixed with fertile basidia. Pileipellis a cutis, hyphae smooth, cylindric, mostly 5–12 µm wide. Stipitipellis without caulocystidia, surface hyphae cylindric, mostly 4–6 µm wide, smooth, thin-walled. Clamp connections abundant in all tissues. TAXONOMIC NOTES: Albomagister leucoloma is described from a single collection made on acidic soil in a cove hardwood forest under Tsuga canadensis and various hardwoods in the Great Smoky Mountains. The species is phylogenetically distinct from, but most closely related to, the clade including A. subaustralis and A. luteifolius; indeed, all three species produce pleurocystidia. Based on the single gathering, we observed the pileus of A. leucoloma to reveal a grayish drab tone at the center, apparently as the thin white fibrillose vesture wears away. In age some yellow to amber-yellow discolorations were also noted on the pileus and stipe surfaces, but the dried specimens were off-white. The species may be distinguished from others by the grayish drab underlying tone to the pileus and somewhat larger spores, and, of course, with phylogenetic evidence. We have only recorded the species once despite years of collecting in the Great Smoky Mountains National Park, so it is comparatively rare or possibly overlooked or misidentified. Albomagister leucoloma equates to Albomagister sp. 3 in Sánchez-García et al. (2014, 2017). Although not analyzed here, an rpb1 sequence was also produced from the type of A. leucoloma —— KU139019 (Sánchez-García and Matheny 2017). ETYMOLOGY: leucoloma (Greek), white fringe, in reference to the overall whitish basidiome coloration DISTRIBUTION AND ECOLOGY: Albomagister leucoloma is known only from the type locality in east Tennessee in the Great Smoky Mountains. It occurred singly on acidic soil at relatively low elevations (<600 m) in a cove hardwood forest mixed with Tsuga canadensis. Basidiomes were recorded in October.