Inonotus dependens (Murrill) Vlasák & Y.C. Dai 2013

Vlasák, Josef, Li, Hai-Jiao, Zhou, Li-Wei & Dai, Yu-Cheng, 2013, A further study on Inonotus linteus complex (Hymenochaetales, Basidiomycota) in tropical America, Phytotaxa 124 (1), pp. 25-36 : 27-30

Inonotus dependens (Murrill) Vlasák & Y.C. Dai , comb. nov. ( Figs.2 , 3 )

MycoBank MB 803766

Basionym.— Pyropolyporus dependens Murrill , North American Flora 9: 106 1908.

Synonyms.— Fomes dependens (Murrill) Sacc. & Trotter, Syll. fung. (Abellini) 21: 292 1912.

Cryptoderma dependens (Murrill) Imazeki, Bull. Tokyo Sci. Mus. 6: 107 1943.

Phellinus dependens (Murrill) Ryvarden, Norw. Jl Bot. 19(3–4): 234 1972.

Fulvifomes dependens (Murrill) Murrill, Mikol. Fitopatol. 26(1): 13 1992.

Fruitbody. —Basidiomata perennial, pileate, dimidiate or semicircular, triquetrous in longitudinal section, without odor or taste, hard corky when fresh, becoming woody hard upon drying. Pilei projecting up to 6.5 cm, 9 cm wide and 6.4 cm thick at base, applanate at first but later ungulate. Pileal surface soon becoming black, concentrically zonate and narrowly sulcate, with conspicuous sharp furrows about 4 per cm, radially cracked with age; margin obtuse, blackish. Pore surface buff-yellow to cinnamon-buff when fresh, cinnamonbuff to cinnamon when dry, glancing; sterile margin distinct, cinnamon-buff, up to 2 mm wide; pores circular,

5–7 per mm, on sloping surface often elongated up to 1 mm; dissepiments thin, entire. Context cinnamonbuff, woody hard, up to 8 mm thick, with a distinct black crust on the pileal surface. Tubes cinnamon-buff to cinnamon, up to 5.6 cm long, tube layers indistinct.

Hyphal structure. —Hyphal system dimitic both in context and trama; generative hyphae simple septate; tissue darkening in KOH, contextual hyphae swollen in KOH.

Context. —Generative hyphae yellow to golden brown, thick-walled, frequently septate, more or less straight, loosely interwoven to more or less regularly arranged, 3–4.5 Μm in diam., swollen to 4–7 Μm in KOH; skeleto-binding alike hyphae present [similar to those in Phellopilus nigrolimitatus ( Romell 1911: 18) Niemelä, T. Wagner & M. Fisch. in Niemelä et al. (2001: 54)], thick-walled with a narrow lumen, occasionally septate, frequently branched, strongly winding, 2–3 Μm in diam.

Tubes. —Generative hyphae yellowish, thin- to slightly thick-walled, occasionally branched, frequently septate, 2–3.3 Μm in diam.; skeletal hyphae dominant, yellowish to yellowish-brown, thick-walled with a wide to narrow lumen, unbranched, loosely interwoven to subparallel along the tubes, 3–4 Μm in diam. Hymenial setae rare to frequent, ventricose or subulate, dark brown, thick-walled, mostly 10–20 × 5–6 Μm, sometimes up to 30 × 8 Μm; basidia clavate, with four sterigmata and a simple septum at the base, 12–18 × 5.5–7 Μm; basidioles in shape similar to basidia, but slightly smaller.

Basidiospores. —Broadly ellipsoid, usually collapsed when mature, yellowish, thick-walled, smooth, CB–, IKI–, 4–4.8(–5) × (3–)3.4–4 Μm, L = 4.37 Μm, W = 3.74 Μm, Q = 1.17–1.18 (n = 60/2).

Specimens examined. — USA. US Virgin Islands, St. John Island , on angiosperm wood , 4 September 2004, J . Vlasák Jr., JV 0409 /12- J ( PRM 861181 , duplicates in JV and BJFC 14696 ) ; 3 September 2004, JV 0409 /1- J ( JV); 5 September 2004, JV 0409 /20- J ( JV); 2 July 2012, JV 1207 /3.4- J ( PRM 861182 , JV, BJFC 14697 ); 3 July 2012, JV 1207 /4.4-J (JV).

Notes.— Inonotus dependens is a common species in American tropics ( Overholts 1953) although it has rarely been collected in recent years (Global Biodiversity Portal, www.gbif.org). The few collections of this species might be caused by the aberrant description by Murrill (1908) that mentions cylindric, seemingly pendant basidiocarp and nearly colorless spores 4 Μm long at most. Other collections (not paratypes) of I. dependens have ungulate basidiocarps and somewhat larger spores as mentioned already by Overholts who knew the species very well and stressed its small setae and black pileus with sharp furrows as more reliable characters. He also suggested that Phellinus dependens may be just a tropical form of P. everhartii that has many similar macro- and microscopical features. However, tramal skeletal hyphae in P. everhartii are frequently simple septate, while they are rarely septate in I. dependens . Moreover, previous phylogenetic study based on mitochondrial small subunit rDNA ( Rizzo et al. 2003) separated P. everhartii from Inonotus , while our phylogeny ( Fig. 1 ) showed I. dependens is a member of Inonotus .

Inonotus linteus and I. cubensis are quite similar to I. dependens and they also occur in Central America. However, I. linteus has subglobose and thicker basidiospores (4.3–5.2 × 3.8–4.7, from holotype). Inonotus cubensis has thick dissepiments (almost as the diameter of pores), thicker context (up to 47 mm), and longer hymenial setae (27–43 × 5–10 Μm, Tian et al. 2013). Inonotus dependens resembles I. weirianus by similar sizes of pores and spores, but I. weirianus has subglobose to ovoid basidiospores (4–5.5 × 3.5–4.5 µm) and grows exclusively on Juglans in southwestern USA ( Gilbertson and Ryvarden 1987).

Figures

FIGURE 1. Phylogeny of Inonotus focusing on the Inonotus linteus complex inferred from ITS sequences. Topology is from maximum likelihood analysis, while bootstrap values are from maximum likelihood (the former) and maximum parsimony (the latter) analyses (only values above 50%). The new species and combinations are in boldface.

FIGURE 2. Basidiocarps of Inonotus dependens (JV 0409/12-J).

FIGURE 3. Microscopic structures of Inonotus dependens (drawn from JV 0409/12-J). a: Basidiospores; b: Basidia and basidioles; c: Setae; d: Hyphae from trama; e: Hyphae from context.