Armillaria altimontana, previously considered North American biological species (NABS) X, is described as new. To date, it appears that A. altimontana prefers higher-elevation, mesic sites within the dry, conifer forest zone of western interior North America. This species has been found on hardwoods and conifers and is associated most commonly with Abies-dominated forest types in southern British Columbia, Washington, Oregon, Idaho and northern California. Partial elongation factor 1-alpha (tef1) sequences were generated from six isolates of A. altimontana originating from three locations in northern Idaho. Phylogenetic analyses of all 10 North American Armillaria species were carried out with maximum parsimony and maximum likelihood. Results indicate that isolates of A. altimontana formed a monophyletic group and clustered with A. calvescens, A. cepistipes, A. gallica and A. nabsnona, which is in agreement with recent phylogenetic studies of Armillaria.
Brazee, N. J., Ortiz-Santana, B., Banik, M. T., & Lindner, D. L. (2012). Armillaria altimontana, a new species from the western interior of North America. Mycologia, 104(5), 1200-1205.
Basidiomata tricholomatoid, pileus plane in mature specimens, up to 3 cm broad in dried samples, rust brown (5E) with cream-colored scales and short fibrils present. Context 0.5-1 mm thick. Dried stipe 4-7 cm long, 8-10 mm broad at base and narrowing to 3-5 mm at the apex; annulus present, cottony, white to cream, robust and thick on two specimens examined, while difficult to observe on the remaining specimen. Rhizomorphs monopodial, and thin, cylindrical on attached substrates.
Basidiospores 7.2-11.7 × 5.4-6.3 µm (n = 20, 9.1 ± 1.5 × 5.8 ± 0.4; Qm = 1.6 ± 0.2), broadly elliptical, smooth, guttulate, hyaline in KOH; nonamyloid in Melzer’s reagent (Fig. 2). Basidia 34.2-55.8 × 6.3-10 µm, cylindro-clavate, four-sterigmate, hyaline in KOH; sterigmata 2.7-4.5 µm long (Fig. 2). Marginal cells among the basidia 24.3-50.4 × 5.4-8.1 µm, clavate to cylindro-clavate, hyaline in KOH (Fig. 2). Pleurocystidia absent. Pileipellis a tangled layer of repent to erect hyphae 4-18 µm broad, subparallel and hyaline in KOH. Hyphae of the pileal scales 6.3-20 µm broad, multiseptate, thin to moderately thick-walled, hyaline or yellowish in KOH. Clamp connections absent.
Holotype. - United States, Idaho: Bonner County, Poirier Creek. Herbarium specimen POR100 designated as the holotype, was recovered on an unknown host in autumn 1983 (collector G.I. McDonald). Dried herbarium sample and live culture have been maintained at the CFMR herbarium (POR100), and a partial tef1 sequence has been deposited in GenBank (accession number JN944606). Isotype deposited at BPI (BPI number 883541).
Habitat. - Found on hardwoods and conifers in higher elevation forests, especially in forest types dominated by Abies species.
Known distribution. – Known from the Cascade, Great Basin and Rocky Mountain ranges in western North America (California, British Columbia, Idaho, Oregon and Washington).