Hydnum alboaurantiacum Swenie & Matheny

Swenie, Rachel A., Baroni, Timothy J. & Matheny, P. Brandon, 2018, Six new species and reports of Hydnum (Cantharellales) from eastern North America, MycoKeys 42, pp. 35-72 : 35

Hydnum alboaurantiacum Swenie & Matheny sp. nov. Figs 3C, D, 6B

Diagnosis.

Most similar to Hydnum albidum but differs from it by the slightly stouter basidiomes that stain bright orange within minutes of handling. Differs from H. subtilior and H. vesterholtii by smaller basidiospores.

Type.

UNITED STATES. North Carolina: Great Smoky Mountains National Park, Smokemont, Bradley Fork Trail (35.5634; -83.3092), scattered under Betula , Fagus , with Tsuga nearby, 28 Jul 2017, R.A. Swenie RAS186 (holotype: TENN 073053).

Etymology.

alboaurantiacum (L.) white-orange, referring to the coloration of the basidiomes, which stain bright orange.

Description.

Pileus 20-70 mm wide, irregularly round, convex, becoming shallowly convex to depressed, occasionally umbilicate; margin thin, wavy to lobed, incurved becoming decurved; surface matt, glabrous, pale to cream white ("Pale Ochraceous Buff"), quickly bruising orange ("Zinc Orange" or "Xanthine Orange", 6A6-8). Spines 1-7 mm long, brittle in mass and breaking easily, adnate to subdecurrent, white to cream-orange ("Pale Ochraceous Buff" to "Light Ochraceous Buff", 4A2-5A3). Stipe 17-50 × 6-21 mm, central or eccentric, terete or clavate, concolorous with the pileus, easily bruising orange (5A2). Context thin, firm, cream white, staining orange ("Xanthine Orange" to "Mars Yellow", 6A8 to 5B6-B7), especially in young specimens at base of stipe within five minutes when cut in half. Odor mild or sweet and fruity. Taste mild.

Basidiospores 4 –4.8– 6(7) μm × 3 –3.9– 5(6) μm, Q=1.00 –1.25– 1.52(1.54) (n=44/6), globose to ellipsoid, smooth, hyaline in KOH. Basidia 36-42 × 4.5-7 μm with 5-7 sterigmata. Pileipellis an interwoven cutis, hyphae smooth, cylindrical, thin-walled, mostly 3-5 μm wide. Clamp connections present.

Distribution.

Southeastern U.S. - North Carolina (type), Tennessee, and West Virginia (GenBank KU612600).

Ecology.

In mixed woods with Quercus , Tsuga , Pinus , Betula , Liriodendron , Fagus . May to August.

Other specimens examined.

UNITED STATES. North Carolina: Great Smoky Mountains National Park, Deep Creek, Indian Creek, on soil in mixed woods, 610 m, 9 Jul 1974, J.H. Restivo JHR1459 (TENN 040599). Great Smoky Mountains National Park, Smokemont, Bradley Fork Trail, scattered under Betula , Fagus , Tsuga , 700 m, 28 Jul 2017, R.A. Swenie RAS186 (TENN 073053). Great Smoky Mountains National Park, Heintooga Round Bottom Road, scattered on embankment with Quercus , Betula , Tsuga , 1525 m, 17 Aug 2017, R.A. Swenie RAS208 (TENN 071751). Macon County, vicinity of Highlands, Glen Falls Trail, 1100 m, 14 Jul 2000, E.B. Lickey TFB9833 (TENN 058812). Transylvania County, Pisgah National Forest, Yellow Gap Road, 310 m, 18 Jul 2000, R.H. Petersen TFB9764 (TENN 058665). Duke Forest, scattered in mixed duff with Quercus , Pinus , 150 m, 25 May 2016, B.P. Looney BPL876 (TENN 073003). Blue Ridge Parkway, near mile marker 342, side of road on embankment, deciduous woodlot, 1225 m, 19 Aug 2016, J. Schieb RAS104 (TENN 073014). Buncombe County, Bent Creek Experimental Forest, near Boyd Branch Road, mossy acidic forest with Quercus alba , Q. rubra , Liriodendron tulipifera , Betula lenta , Tsuga canadensis , 670 m, 22 Aug 2016, M. Hopping MH16004 (TENN 073548). Tennessee: Great Smoky Mountains National Park, Cades Cove, Gregory Ridge Trail, 550 m, 18 Aug 2005, E.B. Lickey TFB12761 (TENN 061328). Great Smoky Mountains National Park, Maddron Bald Trail, on mossy soil with Tsuga , Quercus , Fagus , Pinus , 550 m, 4 Aug 2012, S.A. Trudell SAT1221712 (TENN 067355). Sevier County, University of Tennessee Biology Field Station, on mossy soil with Quercus , Tsuga , Pinus , 450 m, 27 Jul 2009, A.D. Wolfenbarger AW0119 (TENN 064272).

Discussion.

Hydnum alboaurantiacum has probably been mistaken for the closely related H. albidum due to the initial pale white coloration and similar basidiospore size and shape. However, H. alboaurantiacum quickly stains bright rusty orange on all parts of the basidiomes where handled, whereas H. albidum slowly stains a lighter brown-orange hue. In addition, H. alboaurantiacum often displays a larger and more stout stature than H. albidum . The two species are readily distinguished as separate clades in Fig. 2. Hydnum alboaurantiacum is known only from the southeastern US and appears derived from a grade of Central American taxa including the recently described H. zongolicense ( Niskanen et al. 2018).