Xylodon spathulatus (Schrad.) Kuntze, Revisio generum plantarum (Leipzig) 3(2):541 (1898)

Riebesehl, Janett, Yurchenko, Eugene, Nakasone, Karen K. & Langer, Ewald, 2019, Phylogenetic and morphological studies in Xylodon (Hymenochaetales, Basidiomycota) with the addition of four new species, MycoKeys 47, pp. 97-137 : 97

Xylodon spathulatus (Schrad.) Kuntze, Revisio generum plantarum (Leipzig) 3(2):541 (1898)

≡ Hydnum spathulatum Schrad., Spicilegium Florae Germanicae: 178, t. 4:3 (1794).

= Hyphodontia bubalina Min Wang, Yuan Y.Chen & B.K.Cui, Phytotaxa 309(1):50 (2017).

≡ Xylodon bubalinus (Min Wang, Yuan Y.Chen & B.K.Cui) C.C.Chen & Sheng H.Wu, Mycoscience 59:349 (2018).

= Hyphodontia chinensis C.C.Chen & Sheng H.Wu, Mycological Progress 16(5): 554 (2017).

≡ Xylodon chinensis (C.C.Chen & Sheng H.Wu) C.C.Chen & Sheng H.Wu, Mycoscience 59: 349 (2018).

Remarks.

Based on both molecular data and morphology, we place the taxa X. bubalinus and X. chinensis in synonymy under X. spathulatus . In our phylogenetic analysis of ITS sequence data, the recently described X. bubalinus (4 collections) and X. chinensis (2 collections) from China form a well-supported clade with X. spathulatus (4 collections) from Europe (97 BS, 1 PP) that is sister to X. apacheriensis (Fig. 1). Within this clade are several subclades, with very low bootstrap support (<55), thus subspecies or varieties cannot be identified. The 28S rRNA gene analysis also supports conspecificity between X. chinensis and X. spathulatus (99 BS, 0.65 PP) (Fig. 2). Xylodon spathulatus has three main diagnostic features: prominent (1-2 mm tall) aculei of varied shape, numerous apically acute cystidia with 1-4 slight constrictions and capitate cystidia with a resinous cap. It is described and illustrated by Eriksson and Ryvarden (1976) and Langer (1994). Minor morphological variation amongst the three taxa was observed. For example, X. chinensis has ventricose cystidia, similar to those in X. spathulatus , but they are sometimes septate at the constrictions. Distinctly ventricose cystidia were not observed in X. bubalinus , which instead had hyphoid or subulate cystidioles ( Wang and Chen 2017, Fig. 2f). Encrusted hyphal ends at apices of the aculei in X. bubalinus and X. chinensis are typical of those in X. spathulatus . Resinous caps enclosing capitate elements are often absent as in the case of X. bubalinus , X. chinensis , X. spathulatus KAS-GEL2690 (from Germany) and X. spathulatus MSK-F 12931 (from Russia). Spore shape and size are similar amongst the three taxa and the spore quotient 1.3 –1.4(– 1.5) overlaps ( Eriksson and Ryvarden 1976, Wang and Chen 2017, Chen et al. 2017). A few spores in X. chinensis were up to 6 × 5 μm and may be due to better climatic conditions. The description of X. spathulatus is modified to include variable aculei from conical and subulate to distinctly spathuliform and the variable presence of cystidia with resinous caps, mucronate apices and a submoniliform type that are aseptate with more or less blunt apices. Thus X. spathulatus is a highly variable but distinctive species that is widely distributed from northern Europe ( Eriksson and Ryvarden 1976) to southern China ( Chen et al. 2017) and has a preference for old-growth forests ( Dvořák et al. 2017). Reports of X. spathulatus from North and South America ( Ginns and Lefebvre 1993, Hjortstam and Ryvarden 2007b) should be confirmed by molecular sequence data.

Specimens examined.

Xylodon spathulatus - CZECH REPUBLIC: Zofinsky National Park, on dead deciduous wood, leg. M.M. Striegel, 16 Sep 2015 (KAS-MMS 7224); GERMANY: Baden-Wurttemberg, Bad Waldsee, on dead wood of Picea abies (L.) H.Karst., leg. E. Langer, G. Langer, 15 Oct 1992 (KAS-GEL 2690); SWEDEN: Gästrikland, Island Torrö, on dead wood of Betula sp., leg. K.H. Larsson, 29 Sep 1988 (GB KHL 7085, dupl. in KAS); RUSSIA: Udmurtia, near Izhevsk town, on Sorbus aucuparia L., leg. V.I. Kapitonov, 7 Aug 2012 (MSK-F 12931).