Hydnum subtilior 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 subtilior Swenie & Matheny sp. nov. Figs 3G, H, 6D

Hydnum = Hydnum repandum var. album ( Quél.) Rea sensu Am. auct.

Diagnosis.

Hydnum subtilior is most closely related to European H. vesterholtii but differs from it based on ITS molecular data and geographic distribution in eastern North America.

Type.

UNITED STATES. Tennessee: Anderson County, Norris Dam State Park, Clear Creek Trail (36.2124; -84.0681), scattered on soil along trail under Fagus , Carya , Quercus , 24 Jun 2017, P.B. Matheny PBM4093 (holotype: TENN 073034).

Etymology.

subtilior (L.) finer, more slender, in reference to the slim basidiomes.

Description.

Pileus 20-90 mm wide, round or occasionally reniform, convex becoming plano-convex to depressed, sometimes umbilicate; surface matt, glabrous, sometimes cracking into scales at the center, light cream yellow to cream orange buff ("Marguerite Yellow" to "Light Ochraceous Buff", 4A3-A5 to 5A2-A4), yellow with KOH, negative with FeSO4; margin thin, entire, incurved when young then decurved and sometimes wavy in age, staining rusty orange-brown ( “Ochraceous-Orange” to "Mars Yellow", 6A5 to 5B6-B7). Spines 1-8 mm long, adnexed to decurrent, cream white to pale orange-cream (5A1-A2). Stipe 20-60 × 5-21 mm, central or eccentric, sometimes curving, equal or enlarging towards base, cream white or slightly lighter than pileus, staining rusty orange-brown (5B6-B8). Context spongy, cream white to pale orange-cream, slowly staining orange (5A4-6) throughout after five minutes where cut. Odor mild or sweet. Taste mild or pleasant.

Basidiospores 7 –8– 9 μm × 5 –6.3– 7.5 μm, Q=1.07 –1.27– 1.52 (n=51/5), subglobose to broadly ellipsoid, smooth, thin-walled, hyaline in KOH. Basidia 32-44 × 7-9 μm with 3-5(6) sterigmata. Pileipellis an interwoven cutis. Hyphae smooth, cylindrical, thin-walled, mostly 3-7 μm wide. Clamp connections present.

Distribution.

Eastern U.S. - Illinois, North Carolina, Tennessee (type), Georgia, and Florida. Also Michoacán, Mexico (GenBank KY574324).

Ecology.

In hardwoods under Quercus , Carya , Fagus , Carpinus or in mixed woods with these trees or Betula and conifers such as Tsuga or Pinus or less frequently Picea . June to August.

Other specimens examined.

UNITED STATES. Florida: Alachua County, San Felasco Hammock Preserve State Park, Moonshine Sink Trail, in soil with deep layer of leaf litter, forest almost entirely Carya , 75 m, 23 Jul 2017, R.A. Swenie RAS180 (TENN 073050). Alachua County, Sweetwater Preserve off 16th Street entrance, mixed hardwood forest of Quercus , Carya , Carpinus and occasionally Pinus , 35 m, 6 Aug 2017, B. Kaminsky & G. LaPierre (FLAS 61253). Georgia: Putnam County, Rock Eagle 4-H Camp, with Quercus , Pinus , Carpinus , 200 m, 20 Jul 2017, R.A. Swenie RAS170 (TENN 073049). Illinois: Coles County, Lakeview Park, scattered under Quercus alba , Carya , 215 m, 8 Aug 2009, M. Kuo MK08080904. North Carolina: Great Smoky Mountains National Park, Big Creek, Baxter Creek Trail to Mt. Sterling, on soil under Tsuga , 500 m, 9 Aug 2012, P.B. Matheny PBM3868 (TENN 067482). Great Smoky Mountains National Park, Smokemont, Bradley Fork Trail, scattered under Betula , Fagus , Quercus , Tsuga , 700 m, 28 Jul 2017, R.A. Swenie RAS184 (TENN 073051). Great Smoky Mountains National Park, Heintooga Round Bottom Road, solitary with Betula , Picea , 1525 m, 17 Aug 2017, R.A. Swenie RAS207 (TENN 073057). Tennessee: Great Smoky Mountains National Park, Tremont, Middle Prong Trail, scattered singly in mixed woods next to river with Tsuga , Betula , 450 m, 14 Jul 2013, P.B. Matheny PBM3923 (TENN 071999). Great Smoky Mountains National Park, Cades Cove Road, 610 m, 31 Jul 2004, R.H. Petersen TFB12107 (TENN 060045). Great Smoky Mountains National Park, Elkmont, solitary under Quercus , Tsuga , 670 m, 4 Aug 2009, J.M. Birkebak JMB080409-09 (TENN 064273). Great Smoky Mountains National Park, Tremont Institute, Lagoon Trail, solitary under Tsuga , Carpinus , Betula , 450 m, 23 Jun 2017, R.A. Swenie RAS148 (TENN 073035). Great Smoky Mountains National Park, Greenbrier picnic area, solitary in riparian forest under Tsuga , Betula , 500 m, 28 Jul 2017, B.P. Looney BPL987 (TENN 073032). Anderson County, Norris Dam State Park, Clear Creek Trail, solitary in litter on slope under Quercus , Carya , Fagus , 275 m, 31 Aug 2009, A.J. Floden AJF2 (TENN 069607).

Discussion.

Hydnum subtilior is a common species in the southeastern U.S. found in deciduous and mixed forests with a variety of tree associates, often in deep layers of leaf litter. Environmental sequencing has recovered this species from Quercus root tips in central Mexico ( García-Guzmán et al. 2017). The stipe is usually longer than the diameter of the pileus, and the overall coloration can range from light cream-yellow to peach or tan. The best diagnostic features for this species are the coloration and often elongated stature in combination with broadly ellipsoid spores averaging 8 × 6.3 μm. In addition, the context of fresh basidiomes stains orange throughout within five minutes when cut in half (Fig. 3H).

Earlier authors ( Coker and Beers 1951, Smith et al. 1981, Harrison and Grund 1987, Roody 2003) referred to this species as H. repandum var. album , a taxon originally described from Europe.