Hydnum cuspidatum 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 cuspidatum Swenie & Matheny sp. nov. Figs 4B, 5M

Diagnosis.

Closely related to Hydnum umbilicatum but differs from it by ITS sequence divergence as well as more elliptic basidiospores. Known so far in the southeastern and upper midwest United States. Differs from H. aerostatisporum by the smaller basidiomes and slightly larger basidiospores.

Type.

UNITED STATES. Tennessee: Big South Fork National River & Recreation Area, John Litton Farm Trail (36.4960; -84.6700), on soil with Quercus , Tsuga , Pinus , 425 m, 29 Oct 2017, R.A. Swenie RAS246 (holotype: TENN 073068).

Etymology.

cuspidatum (L.), tapering to a fine, sharp point, in reference to the spines.

Description.

Pileus (11)15-50 mm wide, round to oval or irregular and reniform, convex when young, becoming plane or depressed, margin incurved and entire, becoming irregularly wavy or degraded; surface glabrous, sometimes floccose-scaly or scabrous near the umbilicus, dull orange to deep orange-brown (5A6 –6B7– 6D8, “Tawny” to "Mikado Brown"), olive-brown with KOH, at times faded in color towards the margin. Spines 1-8 mm long, shorter near the margin, adnate, pale buff, cream-orange, or tan-orange (7.5YR 8/4-8/6 or 5A3-A5). Stipe 15-50 × 3-10(12) mm, central or eccentric, equal or enlarged towards base, sometimes curved, texture smooth, buff to peach-brown (5A2-A3 to 5B6-C6), sometimes with hazy thin white patches especially towards apex, staining only very slightly light brown (10YR 7/4-7/6 or 5 A–B 7); cottony white basal mycelium often present. Context often hollow, flesh white to cream. Odor not distinctive or sweet and fruity. Taste not distinctive.

Basidiospores (7)7.5 –8.5– 9.5(10.0) μm × 6 –7.2– 8.5 μm, Q=1.01 –1.18– 1.38(1.52) (n=99/6), subglobose to irregularly rounded-elliptic, smooth, thin-walled, hyaline in KOH. Basidia 39-56 × 7-9 μm with 3-4 sterigmata. Pileipellis an interwoven cutis, hyphae smooth, cylindrical, thin-walled, mostly 4-7 μm wide. Clamp connections present.

Distribution.

Eastern U.S. - Michigan (KU612606, MG162266), North Carolina, Tennessee (type), and Georgia.

Ecology.

In deciduous or mixed woods with Quercus , Pinus , Tsuga , Fagus , Betula , Carya , Carpinus , Picea . June to October.

Other specimens examined.

UNITED STATES. Georgia: White County, Unicoi State Park, Unicoi to Helen Trail, solitary with Pinus and mixed hardwoods, 460 m, 16 Jul 2017, R.A. Swenie RAS167 (TENN 073046). North Carolina: Blue Ridge Parkway near Little Switzerland, deciduous woodlot with Quercus and Rhododendron maximum , 1050 m, 19 Aug 2016, H. Hopping RAS106 (TENN 073016). McDowell County, Armstrong Creek, mixed woods, 450 m, 19 Aug 2016, J. Roberts RAS098 (TENN 073008). Great Smoky Mountains National Park, Big Creek Campground, under Tsuga , Carpinus , Betula , Fagus , Quercus , 525 m, 29 Jul 2017, B.P. Looney BPL989 (TENN 073033). Great Smoky Mountains National Park, Cataloochee Divide Trail, solitary with Quercus , Betula , Tsuga , 1525 m, 9 Sep 2017, RAS218 (TENN 073059). Great Smoky Mountains National Park, Balsam Mountain Road, 1525 m, 15 Aug 2005, E.B. Lickey TFB12725 (TENN 073033). Great Smoky Mountains National Park, Heintooga Round Bottom Road, scattered on embankment with Betula , Picea , 1525 m, 17 Aug 2017, R.A. Swenie RAS205 (TENN 073056). Tennessee: Great Smoky Mountains National Park, Tremont, Buckeye Trail, with Tsuga , Betula , 490 m, 23 Jun 2017, R.A. Swenie RAS151 (TENN 073038). Great Smoky Mountains National Park, Schoolhouse Gap Trail, scattered on embankment with Quercus , Betula , Pinus , 550 m, 18 Jul 2017, R.A. Swenie RAS160 (TENN 073043). Anderson County, Oak Ridge, UT Arboretum, on soil in forest with Quercus , Carya , 300 m, 26 Oct 2009, J. Heggan JRH102609-3 (TENN 071998).

Discussion.

Hydnum cuspidatum is closely related to H. umbilicatum and is difficult to distinguish by morphology alone. As in H. umbilicatum , there is high variability in basidiome stature and color. The basidiospores of H. cuspidatum have a slightly higher Q value on average (1.18) than H. umbilicatum (1.06), otherwise phylogenetic analysis of ITS data is needed to distinguish the two species reliably. Hydnum cuspidatum occurs in deciduous or mixed forests in the midwest and southeastern U.S., where it can co-occur with H. umbilicatum .

The ITS sequences of H. cuspidatum have relatively high intraspecific variation (up to 3%) compared to other North American Hydnum species. The lack of distinguishing morphological or ecological features deters further differentiation into separate taxa at this time.