Xerocomellus bolinii J.A. Bolin, A.E. Bessette, A.R. Bessette, L.V. Kudzma, J.L. Frank & A. Farid, sp. nov.
MycoBank number: MB 840863; Index Fungorum number: IF 840863; Facesoffungi number: FoF 10462;
Pileus 4-8 cm wide, convex becoming broadly convex to nearly plane in age; pileus appressed-fibrillose to squamulose with pinkish brown fibrils and white to creamy white context visible in the cracks, dry, staining blue, sometimes slowly or weakly; margin incurved at first remaining so well into maturity, sterile, sometimes undulating, becoming conspicuously cracked with age. Hymenophore tubulose, pale yellow, becoming dull yellow in age, quickly staining dark blue; pores 1–2 per mm, angular to irregular or slightly elongated; tubes 2-6 mm deep, rapidly staining blue when exposed. Stipe: 50–90 × 8–15 mm wide, nearly equal or slightly tapered downward, with a pinched based, solid; surface dry, weakly longitudinally striate, with reddish brown punctae over a whitish to pale yellow ground color often with reddish tints extending from the base upward, staining blue when bruised, basal mycelium white to creamy white. Context of pileus creamy white or a mixture of creamy white and yellow becoming yellow to orange in the stipe and rapidly stains blue when exposed. Odor and taste not distinctive. Macrochemical Testing: Pileus of mature specimens showed light green fading to yellow with NH4OH; younger specimens turn orange with faint green outline of stained area, eventually fading to yellow. Orange to amber, fading to brown with KOH. Older specimens light brown and younger specimens light green with FeSO4. Context in both mature and younger specimens pale orange to NH4OH, orange to amber fading to brown with the application of KOH and yellow with FeSO4. Cuticle stains light green, fading to yellow, reaction with NH4OH; younger specimens develop orange with a faint green outline that eventually fades to yellow; KOH produces orange to amber that fades to brown; with FeS04 mature specimens turn light brown, and younger specimens light green.
Basidiospores light brown to olive-brown in fresh deposit, (10–)12–13(–14) × 4.5–6 µm, n = 30, Q = 2.40, elliptical in face view, obscurely inequilateral in profile, thin-walled, smooth, lacking an apical pore, pale grayish yellow in KOH, dull yellow in Melzer’s. Basidia 32-36 × 9-12 µm, mostly clavate, occasionally cylindro-clavate, 2(4)-sterigmate, hyaline in KOH, grayish yellow in Melzer’s. Basidioles 21.5–30 × 6.5–10 µm, clavate. Hymenophoral trama boletoid, with lateral elements, 5-8 µm wide, moderately divergent, hyaline in KOH, grayish yellow in Melzer’s. Pileipellis a tangled layer or repent tubular hyphae, 5–9.5 µm wide, with cylindrical, rounded to slightly inflated end cells, thin-walled, smooth, hyaline in KOH, yellowish in Melzer’s. Pileus trama hyphae loosely interwoven, 5–11 µm wide, smooth, thin-walled, hyaline in KOH or Melzer’s. Cheilocystidia and pleurocystidia scattered, 36–48.5 × 9–11.5 µm, fusoid-ventricose, smooth, thin-walled, hyaline to ochraceous in KOH, ochraceous in Melzer’s. Stipitipellis hyphae mostly parallel, slightly interwoven, 4.5–9.5 µm wide, hyaline to yellowish in KOH or Melzer’s, with fascicles of clavate to distorted caulocystidia 34–52 × 9–21 µm, that are dull yellow to brownish yellow in KOH or Melzer’s. Stipe trama subparallel, interwoven, 5–11.5 µm wide, hyaline to yellowish in KOH or Melzer’s. Clamp connections absent.
Material examined: USA, Florida, Broward County, Davie, Tree Tops Park, 14 Oct 2017, J.A. Bolin 124 (USF holotype 301494); Lake County, Lake Louisa State Park, Clermont, 13 Jun 2020, A. Farid 1047 with R.E. O’Donovan, C. Matson, and J.A. Bolin (USF 301498); Palm Beach County, Delray Beach, Morikami Museum and Japanese Gardens, 23 Sep 2017, Jason Bolin 110 (USF 300098); ibid., 17 Oct 2018, J.A. Bolin 232 (USF 300082); ibid., 12 Sep 2018, J.A. Bolin 208 (USF 301486); West Palm Beach, Okeeheelee Park, 20 Nov 2017, J.A. Bolin 133 (USF 300094); ibid., 13 Nov 2018, J.A. Bolin 238 (USF 301485); ibid., 23 Nov 2018, J.A. Bolin 274 (USF 301484).
Distribution: Solitary or scattered in sandy soil associated with Quercus and Pinus, along woodland edges, typically near saw palmetto (Serenoa repens) and/or cabbage palm (Sabal palmetto). Currently only documented from Florida. There are several images that we believe to be X. bolinii on the citizen science platform MushroomObserver.org (observation nos.: 430943, 412138, 293427, 289394), but no herbarium samples were made.
Notes: Xerocomellus chrysenteron is similar but has a dark olive to olive-brown or greyish-brown cracked cap with exposed red to pinkish context, stains slowly or erratically greenish-blue on the hymenophore and cap context and has a more northern distribution. Xerocomellus zelleri has a dull black to blackish-brown or dark olive-brown pileus, context that is white to pale yellow that is unchanging or sometimes bluing and is reported from the Pacific Northwest south to California and into Mexico.