Hydnellum fagiscabrosum A.M. Ainsw. & Nitare, 2021

Nitare, J., Ainsworth, A. M., Larsson, E., Parfitt, D., Suz, L. M., Svantesson, S. & Larsson, K. - H., 2021, Four new species of Hydnellum (Thelephorales, Basidiomycota) with a note on Sarcodon illudens, Fungal Systematics and Evolution 7 (1), pp. 233-254 : 238-245

Hydnellum fagiscabrosum A.M. Ainsw. & Nitare , sp. nov.

MycoBank MB 837984. Figs 4A, C–F , 9A .

Etymology: Epithet derived from fagi -, referring to the association with Fagales (e.g. Castanea , Fagus and Quercus ) and scabrosum , referring to the morphological similarity to Hydnum scabrosum Fr.

Typus: Sweden, Blekinge, Ronneby, north-eastern shore of lake Listersjön , close to a picnic area, near Fagus sylvatica , 56.320946 / 15.350357, 3 Sep. 2014, J. Nitare (holotypus GB-0195805 ; isotypi K(M)264450 , UPS); GenBank accession: MW144294 .

Misapplication: Sarcodon scabrosus (at least in part) sensu European authors.

Selected illustrations (all labelled as S. scabrosus ): Breitenbach & Kränzlin [1986: 235 (no. 279)], Maas Geesteranus (1975a: taf. 34 abb. a), Pegler et al. (1997: fig. 77 showing micromorphology of specimen K(M)30165 sequenced by Brock et al. 2009).

Description: Basidiomata terrestrial, stipitate, medium to rather large and fleshy, solitary or clustered, ofen in small groups. Pileus 50–140 mm broad, irregularly rounded to lobate, initially convex, umbonate or plane, usually developing a depressed centre at maturity;margin thin,undulating and initially incurved; cuticle radially fibrillose, showing superficial tearing to produce marginal areolae and zones of concentric scales, sometimes terminating in an upturned pointed darker tip, and deeper tearing to produce radial fissures in the underlying paler context and a central zone of coarse block-like scales; initially pinkish red brown, sometimes showing lilac or pale violaceous tints, with whitish growing edge, becoming progressively darker towards the centre and entirely chestnut brown or black brown with age. Stipe 30–100 × 10–30 mm, cylindrical or basally tapered with smooth, scaly, longitudinally fibrillose texture or covered by rudimentary or entire spines; concolourous with the pileus at the apex and distinctly bluish-green to black at the base with whitish mycelium binding the soil. Spines not, slightly or strongly decurrent,up to 10 × 1 mm, light greyish brown with whitish tips at first, becoming progressively browner from the base. Flesh not zoned, whitish, with distinctive greyish- or bluish-green patch within the base of the stipe, smell farinaceous, taste farinaceous and bitter. Chemical reaction: when a drop of 3 % KOH is added to dry specimens, the pileipellis becomes darker brown and the flesh becomes pale brown. Hyphal system monomitic,all hyphae simple septate, tramal hyphae of spines up to 8 µm wide. Basidia clavate, with four sterigmata. Basidiospores brown, subglobose or short ellipsoid, irregularly tuberculate, with oblique apiculus, 4.5‒6.3(‒6.4) × (3.5‒)3.8‒5.3(‒5.6) µm, av. = 5.4 × 4.7 µm, Q = 0.9‒1.5 (n = 4/100, measurements from the lateral side without tubercles), tubercles numerous, up to 1.3 µm high, with rounded, flat-topped or exsculpate apices.

Ecology and distribution: We conclude that this species is ectomycorrhizal from the placement of GenBank sequence MF946050 which was obtained from an American ectomycorrhizal root tip of Quercus section Lobatae and identified as S. scabrosus in Rasmussen et al. (2018). From field observations we infer that H. fagiscabrosum is a mycorrhizal partner of Fagus sylvatica , Quercus spp. and Castanea sativa , including coppiced non-native Castanea in the UK. It is mostly found in the nemoral vegetation zone in sandy or gravelly soils, usually with other stipitate hydnoids, and ofen on mossy embankments, tracksides, ditchsides or in similarly nutrient poor microhabitats. The true extent of its European distribution is currently unknown due to its former inclusion within the circumscription of S. scabrosus , but we have produced molecular evidence for its presence in Norway, Sweden, UK and Italy and therefore suspect it is a very widespread, albeit relatively uncommon, member of the European Fagaceae -associated stipitate hydnoid community. Placement of GenBank sequences in Fig. 3 demonstrate that H. fagiscabrosum is also present in the southeastern USA in Florida, North Carolina and Tennessee where it has been assigned to S. scabrosus ( Hughes et al. 2009, Baird et al. 2013, Rasmussen et al. 2018).

Additional specimens examined: Italy, Liguria, Savona, Sassello,Badami, on soil near Castanea sativa , 2 Sep. 2010, F. Boccardo K(M)197487 (as S. regalis ) . Norway, Agder, Tvedestrand, N of Øynesvann, trackside in Quercus forest, 23 Aug. 2014, I.-L. Fonneland & D. Pettersen O-F-251442 . Sweden, Bohuslän, Lysekil par., Vägeröds dalar, on soil with Quercus sp. and Tilia cordata, E. Larsson GB-0195727 ; Sotenäs and Tossene par., Hogsäm, on soil under Fagus sylvatica , R.-G. Carlsson GB-0195621, GB-0195625 ; Tanum par., Lindö, on soil with Quercus sp. , Tilia cordata , and Corylus avellana, J. Olsson GB-0195622 ; Västergötland, Sätila par., Ramhultafallet, on soil with Quercus sp. and Corylus avellana , R.-G. Carlsson GB-0195621 . UK, Berkshire (VC22), Windsor Crown Estate, on soil near Castanea sativa , 28 Sep. 1979, R. Phillips K(M)119189 (as S. scabrosus ) ; Windsor Crown Estate, Buttersteep area (dry ditch), (SU9065), on soil near Castanea sativa , 2 Sep. 2005, A.M. Ainsworth K(M)197477 (as S. scabrosus ) ; Windsor Crown Estate, Buttersteep Hill, (SU9066), on soil near Castanea sativa , 29 Sep. 2008, A.M. Ainsworth K(M)197472 (as Sarcodon sp. ) ; East Norfolk (VC27), St Faith’s Common (TG181173), on soil near Castanea sativa , 22 Sep. 2011, A. Crotty K(M)197476 (as S. scabrosus ) ; South Hampshire (VC11), New Forest, Brock Hill area (SU27020553), on soil near Quercus sp. and Fagus sylvatica , 9 Oct. 2011, M. Nesbitt K(M)172590 (as S. scabrosus ) ; New Forest, Roydon Woods (SU313000), on soil, 11 Sep. 2002, A. Leonard K(M)181351 (as S. scabrosus ) ; New Forest, Vinney Ridge (SU26290518), on soil near Quercus sp. , 17 Sep. 2010, A. Lucas Hyd229 (as S.scabrosus ) ; Surrey (VC17), Witley Common (SU92553982), on soil near Quercus sp. and Castanea sativa , 13 Sep. 2008, L. Goodwin K(M)160940 (as S. scabrosus ) ; Woking (TQ018605), on soil near Quercus sp. , Castanea sativa and Pinus sylvestris , 31 Jul. 2007, R.A. Alder K(M)162048 (as S. scabrosus ) ; ibid., 6 Sep. 2011, R.A. Alder K(M)171979 (as S. scabrosus ) ; West Kent (VC16), Seal Chart (TQ567557), on soil near Quercus petraea , 11 Oct. 2010, J. Pitt K(M)197490 ; Tudeley Woods, on soil near Castanea sativa , 24 Sep. 1994, N. Fletcher K(M)30165, (as S. scabrosus ) ; ibid., 15 Oct. 1999, J. Weightman K(M)64653 (as S. scabrosus ) .

Notes: Historically, our species has been included in a broad concept of Sarcodon scabrosus which has an inferred association with both Fagaceae and Pinaceae , at least in Europe. However, based on its protologue, the discussion in Maas Geesteranus & Nannfeldt (1969) and the clustering of a sequence derived from its neotype with several sequences derived from coniferassociated basidiomata and mycorrhizal root samples (see Fig. 3 ), Hydnellum scabrosum sensu stricto was revealed to be an ectomycorrhizal partner of Pinaceae only. More specifically, it was detected in the roots of Pinus sylvestris in Estonia (UNITE UDB008050), of Pinus densiflora (GenBank AB251833) in Japan ( Lian et al. 2006) and of Pseudotsuga menziesii (GenBank KM402896) in Canada ( Kranabetter et al. 2015). Furthermore, European basidiomatal sequence and collection data indicate that it is usually found on poor sandy soils with P. sylvestris and never in pure stands of Fagaceae . It should also be noted in passing that the placement of GenBank sequence AF351870 in Fig. 3 indicates that, in Oregon at least, H. scabrosum sensu stricto can also form mycorrhizal associations with epiparasitic monotropoid plant roots ( Bidartondo & Bruns 2001).

Hitherto, H. fagiscabrosum was recognized as “ Sarcodon sp. 1 (with Fagaceae )” in the UK ( Smith et al. 2016) and as “ H. fagiscabrosum nom . prov. ” in Sweden ( Nitare 2019). We have not been able to find any usable existing name for this misinterpreted species, and old names such as Hydnum amarescens Quél. , a fairly pale and minutely scaly species with a non-existent type fide Maas Geesteranus (1956), are all dubious and have been applied to other species (see e.g. discussion in Maas Geesteranus & Nannfeldt 1969). Therefore, we prefer to give this widely distributed species a new name.

The basidiomata of H. fagiscabrosum , H. illudens and H. scabrosum are similarly coarsely scaly when fully mature, but these species differ in their pileal pigmentation and ecological associations. In the field, H. fagiscabrosum can be distinguished from H. scabrosum by the relatively persistent, ofen broad and contrastingly whitish pileal margin of the former and its association with Fagaceae . Hydnellum scabrosum has a more concolorous pileal margin and it associates with Pinaceae . Although H. illudens and H. fagiscabrosum might be found in similar habitats in southern Europe, they differ in basidiomatal colours. The pileal surface is yellowish brown in H. illudens and the dried flesh also assumes a yellowish colour, whereas the pileus is reddish brown in H. fagiscabrosum and the flesh remains greyish when dried. Furthermore, basidiomata of H. illudens have a strongly farinaceous taste, whereas those of H. fagiscabrosum are rather sour and acrid.

Hydnellum fagiscabrosum is distinguished from H. nemorosum and H. lepidum , both of which are associated with broadleaved trees, by its more coarsely scaly pileus. Of these species, H. nemorosum differs the most with its pinkish to vinaceous-brown pileus which is fissured but not really scaly, whereas in H. lepidum the scales are small and more or less adpressed all over the pileal surface.

Figures

Fig. 4. A. Hydnellum fagiscabrosum GB-0195727. B. Collecting site for GB-0195727. C. H. fagiscabrosum holotype, GB-0195805. D. H. fagiscabrosum O-F-251442, photo I.-L. Fonneland. E. H. fagiscabrosum Hyd229, photo A. Lucas F. H. fagiscabrosum GB-0195622, photo J. Olsson. G. Hydnellum lepidum DMS-680077, photo T. Borgen.H. H. lepidum GB-0202073.

Fig. 9. Hydnellum basidiospores. A. H. fagiscabrosum (holotype, GB-0195805). B. H. glaucopus (GB-0195722). C. H. illudens (GB-0195937). D. H. lepidum (GB-129373). E. H. nemorosum (O-F-242352). F. H. roseoviolaceum (holotype. GB-0195936).G. H. scabrosellum (holotype, GB-0195689). H. H. scabrosum (GB-0195731). Scale bar = 5 µm.

Fig. 3. Phylogram of Hydnellum section Scabrosi. Maximum Likelihood tree based on nuclear ribosomal ITS sequences. Numbers on branches represent reliable support values from SH-aLRT test (≥ 80 %), ultrafast bootstrap (≥ 95 %), and Bayesian inference posterior probability values (≥ 0.95),respectively.Terminal names are the original identification. Sequences from type specimens are marked in bold face.Sequences not generated from basidiomata are marked as env(ironmental).