Albomagister subaustralis Sanchez-Garcia, Birkebak & Matheny

Albomagister subaustralis (A.H. Sm. & Hesler) Sánchez-García, Birkebak & Matheny, Taxon 63: 1000 (2014) Figs. 5A–5B, 7A– 7C. = Hygrophorus subaustralis A.H. Sm. & Hesler, Lloydia 5: 46 (1942) Habit tricholomatoid, resembling small forms of Tricholoma columbetta. Pileus 27–44 mm wide, bluntly conical with an inflexed margin when young, expanding to plano-convex or applanate with age, with a broad umbo; surface dull, matte, felted and slightly radially fibrillose towards the margin; white, at times yellowish at the center, not hygrophanous; context white and dull, odor mild or somewhat unpleasant, not farinaceous. Lamellae sinuate, close with several tiers of lamellulae, slightly yellowish white, broad (up to 7 mm deep), edges concolorous and entire in appearance. Stipe 45–55 × 5–10 mm, equal, at times somewhat flexuous, fragile; surface dry but on occasion with beads of moisture at the apex, tomentose on the lower part, veil absent; white; stuffed to hollow. Basidiospores 4– 4.6 – 5(5.3) × 3.5– 3.8 –4(4.3) µm, Q 1.10– 1.25 –1.40 (n = 61/3), broadly elliptic to subglobose, at times with a guttule, hyaline, thin-walled, inamyloid and nondextrinoid, with a distinct apiculus, white in deposit. Basidia 20–28 × 5–6 µm, 4-spored, narrowly clavate to cylindric, hyaline, thin-walled. Pleurocystidia 26–56 × 8–15 µm, narrowly utriform or fusiform to utriform, rarely oblong to obovate, with rounded or obtuse apices, long pedicellate, thin-walled, hyaline; scattered, somewhat more frequent towards the fertile lamellar edges. Cheilocystidia similar to pleurocystidia, at times slenderly clavate, scattered and mixed with fertile basidia. Pileipellis a cutis giving rise to upright and constricted to flexuous cylindric hyphae, 3–9 µm wide, thin-walled, hyaline. Stipitipellis without caulocystidia, hyphae of stipe surface 3– 5 µm wide, hyphae appressed or somewhat recurved, smooth, thin-walled, hyaline. Clamp connections present in all tissues. TAXONOMIC NOTES: Albomagister subaustralis is the most commonly collected species of Albomagister in the southern Appalachians. It also produces the largest basidiomes among the white-colored species. Albomagister luteifolius is similar but is characterized by the smaller Inocybe geophylla- like basidiomes. Albomagister leucoloma differs from A. subaustralis by the pileus with grayish drab tints and unique phylogenetic position. DISTRIBUTION AND ECOLOGY: Albomagister subaustralis is known only from the southern Appalachians (Georgia, North Carolina, South Carolina, Tennessee) in rich and poor (acidic) cove hardwood forests (<1000 m elev) mixed with hemlock and/or pine and also in oak-hickory-beech forests on karst topography. Potential ectomycorrhizal trees include Tsuga, Betula, Carpinus, Carya, Fagus, Quercus, Pinus, and Tilia. Reports from outside the southern Appalachians have not been confirmed with molecular annotations. Most basidiomes were observed from August to October. ADDITIONAL SPECIMENS EXAMINED: USA, North Carolina, Swain County, Great Smoky Mountains National Park (GSMNP), Indian Creek, 23 August 1942, L. R. Hesler & A. J. Sharp LRH14423 (TENN-F-014423); ibid., 12 September 1947, L. R. Hesler LRH17951 (TENN-F-017951); ibid., L. R. Hesler & A. J. Sharp LRH18628 (TENN-F-018628); ibid., 14 August 1952, L. R. Hesler LRH020463 (TENN-F-020463); Martins Gap, GSMNP, beside the trail, 2 September 1938, A. H. Smith AHS10844 (holotype, MICH 10951); South Carolina, Oconee County, Oconee State Park, Mountain Rest, 22 September 2013, J. M. Birkebak JMB092213-01 (TENN-F-070997); Tennessee, Blount County, GSMNP, Cades Cove, 25 September 1957, L. R. Hesler LRH22663 (TENN-F-022663); ibid., 26 August 1958, L. R. Hesler LRH023195 (TENN-F-023195); ibid., campground area of Cades Cove, 6 August 1959, L. R. Hesler LRH23221 (TENN-F-023221); ibid., 26 September 1973, L. R. Hesler LRH39069 (TENN-F-039069); Cocke County, GSMNP, Maddron Bald Trail, 4 August 2012, S. A. Trudell SAT-12–217-02 (TENN-F-067343); Monroe County, Tellico Plains, Bald River Falls, Cherokee National Forest, 1 October 2011, W. Burnette WBU11 (TENN-F-066902); Sevier County, GSMNP, Elkmont area, Jakes Creek Trail, 4 August 2009, M. G. Wood MGW676 (TENN-F-064620); ibid., E. C. Vellinga ECV4049 (TENN-F-064621); Sevier County, GSMNP, Greenbrier area at intersection of Greenbrier Road and Ramsey Prong Road, Cemetery Trail, 2 September 2013, M. G. Wood MGW1296 (TENN-F-068710).