Descolea alienata Horak & Desjardin

Holotypus: U.S.A., Hawai`i, Kaua`i, 8 Jan. 1994, D. E. Desjardin 6025 (SFSU).
Isotypus: ZT 5206; BISH.

Etymology. alienatus (Lat.) = alien, stranger; indicating that the species is not a component of the native mycota of the Hawaiian Islands.
Pileus (FIG. 3) 20-30(-40) mm diam, campanulate when young, expanding in age to broadly campanulate, then often plano-umbonate, often with a depression on 2-3 sides of the umbo but not all the way around; margin decurved to horizontal, often splitting in age, not striate; surface weakly radially corrugated-wrinkled to the smooth disc, hygrophanous, glabrous; at first dark brown (7F7-8) to dark reddish brown (8F7-8) overall, remaining so on disc and margin fading to brown (7E7-8), then fading overall to light brown (6D5-6) or brownish yellow (5C5-6; "clay color") with moisture loss. Context thin (<1.5 mm), watery concolorous with pileus surface. Odor not distinctive; taste mildly mealy or slightly fungal. Lamellae ascending-adnate to adnexed, distant with 3 series of lamellulae, convex, broad (4-7 mm), light brown (7D5-6) when young, brown (6-7E7-8) in age with a buff colored margin. Stipe 15-28 X 2-3 mm, central, terete, ±equal, silky-canescent overall with a few velar squamules below the annulus, hollow; surface at first buff or dingy buff overall, soon pale greyish orange (5B3) then light brown (6-7D4-5; "hazel") to brown (7E4-6) in age, often with a narrow white to buff zone at apex; annulus membranous, relatively thick, non-striate, with tomentose margin, persistent but easily removed, central to inferior, greyish orange (6B3) to brownish grey (6C3).
Basidiospores (14.0-)15.0-17.5(-18.5) X 7.5-9.5 µm (mean = 16.1 ± 1.0 X 8.7 ± 0.6 µm, Q = 1.6-2.0, Q mean = 1.8 ± 0.1), amygdaliform to limoniform, dark rusty brown, coarsely roughened overall or with a smooth distal end, with a distinct perispore 0.4-0.8 µm thick (not included in spore measurements), no germ pore, no plage, with a prominent hyaline hilar appendage, inamyloid. Basidia 40-47 X 9.5-11.5 µm with sterigmata 5-8 X 2.5-3.5 µm, 2 spored, subcylindric to clavate, hyaline, clamped. Basidioles subclavate. Lamellar edge sterile; cheilocystidia numerous, 25-35 X 6.5-10.0 µm (at broadest), consistently lecythiform; capitulum 3.3-4.0 µm diam with supporting neck 1.0-1.8 µm diam, hyaline, thin-walled. Pleurocystidia similar to cheilocystidia but typically slightly narrower, common to uncommon, inconspicuous and not projecting among basidia and basidioles. Pileipellis a palisade or poorly developed epithelium composed of subcylindric, clavate or broadly clavate cells, 16-40(-50) X 8-24 µm; cells in 1-2 layers; walls pale tawny, mostly nonincrusted or weakly incrusted on lower portion of cell, nongelatinous; pileipellis cells arising from a thin subcuticular layer of interwoven, repent to curved-erect, cylindric hyphae 3-9 µm diam, heavily incrusted with dark brownish orange to brown pigments, with walls thin, brownish orange, nongelatinous. Pileipellis on pileus disc overlaid by a thin universal veil tissue composed of repent, loosely interwoven, cylindric hyphae 4.0-6.5 µm diam, with hyaline to pale yellowish walls incrusted with pale yellowish brown to brownish orange pigments. Pileus and lamellar tramas composed of subparallel to slightly interwoven hyphae; hyphae 6-18 µm diam, cylindric to inflated, typically nonincrusted or weakly incrusted nearest to subcutis, with hyaline to pale tawny walls, nongelatinous. Stipe tissue monomitic; cortical and medullary hyphae similar, parallel, cylindric, 3-8 µm diam, hyaline to pale brownish orange, nongelatinous, with cortical hyphae weakly incrusted and medullary hyphae nonincrusted. Stipitipellis undifferentiated or of a few loosely interwoven cortical hyphae; caulocystidia absent. Partial veil tissue from annulus of interwoven hyphae 3-8(-10) µm diam, hyaline to very pale brownish orange, smooth or weakly roughened. Clamp connections common in all tissues.
Habit, habitat and distribution. Scattered, common in soil under black-wattle acacia (Acacia mearnsii De Wild.; Fabaceae) in mixed Native and Alien Forest dominated by black-wattle acacia, with scattered strawberry guava (Psidium cattleianum Sabine; Myrtaceae), ohi`a (Metrosideros polymorpha Gaud.; Myrtaceae) and koa (Acacia koa A. Gray; Fabaceae). Putatively mycorrhizal with black-wattle acacia (native to New South Wales and Tasmania, Australia), a tree now naturalized in the Hawaiian Islands that was first introduced onto Lana`i in 1911. Known from only the type locality. January.
Specimens Examined: U.S.A. HAWAII: Kaua`i, Koke`e State Park, Pu`u Ka `Ohelo Berry Flat Trail, between N22°ree; 07.158', W159°ree; 38.725' and N22°ree; 08.158', W159°ree; 38.585', 1120-1150 m, 8 Jan. 1994, DED 6025 (HOLOTYPE, SFSU; ISOTYPE, BISH, ZT 5206); same location, 7 Jan. 1995, DED 6193.
Commentary. Descolea alienata is characterized by the following combination of features: broadly campanulate, radially corrugated, dark reddish brown pileus; brown lamellae; small pallid stipe with a persistent central greyish orange annulus; large, coarsely roughened, amygdaliform basidiospores; bisporic basidia; lecythiform pleurocystidia and cheilocystidia; and growth with black-wattle acacia. The species is unusual in the genus because of the very large basidiospores and lecythiform hymenial cystidia, and it represents the only known species of Descolea putatively mycorrhizal with the Fabaceae; all other species reported are associated with Fagaceae, Myrtaceae or Pinaceae (Horak, 1971). Although several myrtaceous trees occur approximately 10 m from the population of D. alienata, we suspect that D. alienata is not mycorrhizally associated with them. Ohi`a (Metrosideros polymorpha), an endemic myrtaceous tree, does not support ectotrophic fungi (pers. obs.). Strawberry guava (Psidium cattleianum) is one of the more common, invasive alien plants that forms dense thickets on all major Hawaiian islands. Extensive collecting over many years in this habitat throughout the Hawaiian Islands has never yielded specimens of D. alienata. In addition, a concerted effort to find D. alienata in a thicket of strawberry guava located adjacent to the stand of black-wattle acacia from which all known specimens of D. alienata were collected proved unsuccessful. Although only circumstantial, these data suggest that D. alienata is associated with black-wattle acacia.
Descolea alienata is most closely allied with Descolea rheophylla (Bertault & Malençon) Malençon, a species associated with Eucalyptus in Morocco. Descolea rheophylla differs, however, in forming smooth, noncorrugated pileus, rhubarb-colored lamellae, shorter and broader basidiospores (14-16 X 9.2-10.8 µm, mean = 15.0 X 9.5 µm), and habit with exotic Eucalyptus (fide Malençon & Bertault, 1970; Malençon, 1979). This is the first report of a species of Descolea from the central Pacific region. We presume that D. alienata was introduced to the Hawaiian Islands along with black-wattle acacia probably of Australian origin. Lecythiform cystidia are unusual in Descolea, known from only two other species; viz., D. rheophylla as hymenial cystidia (Malençon & Bertault, 1970), and D. maculata Bougher where they occur only on hyphae associated with mycorrhizal rootlets but not on basidiomata (Bougher & Malajczuk, 1985). The genus Descolea, the center of biodiversity of which is in the southern hemisphere Pacific rim (Horak, 1971), has been found a number of times in northern hemisphere exotic plantations; e.g., D. antarctica Sing. from Faröes Islands under Nothofagus (J. Vesterholt pers. comm.), D. maculata Bougher from Spain under Eucalyptus (Moreno et al., 1994), D. rheophylla from Morocco under Eucalyptus (Malençon & Bertault, 1970), and Descolea sp. from Ireland under Nothofagus (R. Watling, pers. comm.).

Bougher, N. L., and N. Malajczuk. 1985. A new species of Descolea (Agaricales) from

Western Australia, and aspects of its ectomycorrhizal status. Australian J.
Bot. 33: 619-627.
Horak, E. 1971. Studies on the genus Descolea Sing. Persoonia 6: 231-248.
Malençon, G. 1979. Champignons du Maroc. Beih. Sydowia 8: 258-267.
________, and R. Bertault. 1970. Flore des champignons supérieurs du Maroc. 1.
Rabat. 601 pp.
Moreno, G., E. Horak, and M. Lago. 1994. Descolea maculata Bougher (Agaricales),
nueva cita para Europa. Crypt. Mycol. 15: 255-261.

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