Auriscalpium greyorum L.J.Vaughan, B.Clauss & T.W.May sp. nov.

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MB 848128

Type: AUSTRALIA, VICTORIA, Blackwood, Jack Cann Reserve, 1 July 2007, Field Naturalists Club of Victoria Fungi Group 69 (holotype MEL 2323326). GenBank: ITS = OQ750677.

Synonymy: Auriscalpium sp. ”Blackwood” as used in May (2019).

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Figure 2 Macroscopic features of Auriscalpium greyorum. a,b Sporing bodies in habitat, on bark of living Eucalyptus radiata (MEL 2524521). Photographs by Reiner Richter (CC) BY-NC-SA c Pileus shape in side-view (MEL 2524521) d Cross-section of sporing body embedded in bark substrate, stipe and pileus surface with a layer of dense fine fibrils (MEL 2524521) e Detail of spines (MEL 2524522) f Cross-section of sporing body when drying, with stipe embedded in bark substrate (MEL 2524894). Scale=1 mm.

Figure 3 Microscopic features of Auriscalpium greyorum. a–c,e–i in 5% KOH; d in Melzer's reagent.

a (H: MEL 2323326) b,c (MEL 2305170) Basidia and basidioles d Amyloid spores with finely verrucose ornamentation, on spine (MEL 2305170) e Pileipellis with bristle at low magnification (H: MEL 2323326) f Pileipellis at higher magnification with interwoven, erect, hyaline bristle formation, pigment-banded subpellis and emergent gloeoplerous hyphae (H: MEL 2323326) g Pileus trama just below pileipellis (H: MEL 2323326) h Spine with pleurogloeocystidia at edge, and cheilogloeocystidia at apex (MEL 2524522) i Pleurogloeocystidia emergent above hymenium, with right-angle bend and bump near bend, arising from parallel hymenophoral trama (MEL 2305170). Scale a–d,f–i=10 μm; e=100 μm.

Basidiomes annual, pileate, laterally attached to substrate with reduced stipe. Pileus (3–)6–19 mm wide, 6–10(–14) mm deep horizontally from bark attachment to margin, up to 4 mm high from top of pileus to margin, semi-circular to kidney-shaped in top-view, side view hemispherical or campanulate, then plano-convex to almost plane; at first reddish brown (8D7), then chocolate brown (6F4), with darker patches of dark brown (9F8) at margin and in radial fibrils, often paler toward margin when young, often very dark brown when old; surface texture sparsely hispid, often more dense near attachment to bark and on younger specimens, bristles up to 1 mm, erect or forming appressed radial fibrils when flattened, hyaline to pale buff (4A2–3) to greyish red (8B6); margin wavy, becoming campanulate, splitting radially, sometimes becoming inrolled when dry, not transluscent-striate. Spines pendant, up to 4 mm long, 0.2–0.5 mm diameter at base, close, terete, tapering slightly toward apex, apex rounded or acute, if acute, with vinaceous portion at apex; at first spines strongly decurrent running down stipe, spines more well-developed on stipe than underside of pileus, then later sometimes not decurrent, spines more well-developed close to stipe and less-developed closer to margin; almost white (1A1) to greyish white (1B1) to pale buff (1B3), sometimes with reddish tinge, with white dusting under lens. Stipe 1–4(–7) mm long, 1–2(–3) mm diameter, mostly embedded in bark, up to depth of 2–3 mm, sometimes narrowing in middle with slightly bulbous base; brown (6F4), with similar variations to pileus; surface with a layer of dense fine fibrils, from which arises erect, hispid processes that are up to 1 mm long, hyaline to pale buff (4A2) to greyish red (8B6); the fibrous layer with hispid processes contiguous with similar layer at base of pileus. Context. In pileus, 0.5–2 mm deep, concolourous with surface, or with very fine scattered pale buff mottling, when drying, pale buff (4A2–3), contiguous with stipe context; in stipe, similar in colour to pileus context; in spine, buff (4A3), to greyish red (8B6) when old.

Hyphal system monomitic, with septate, thick-walled generative hyphae (2–)3–6(–10) μm wide, and aseptate, thin-walled gloeoplerous hyphae 3–7 μm wide. Clamp connections detected in all tissues except gloeoplerous hyphae. Trama in pileus and stipe, consisting of interwoven generative hyphae, cylindrical or varying in diameter, sometimes inflated in sections, often slightly flexuose, branching, sometimes with right-angled branches, with occasional gloeoplerous hyphae, cylindrical; in spine consisting of parallel generative hyphae, cylindrical to slightly inflated or fusiform, often with short segments, gloeoplerous hyphae cylindrical, often slightly flexuose, sometimes with right-angled bend, terminating as cystidia arising above basidia. Subhymenium narrow, consisting of interwoven, parallel, generative hyphae. Pileipellis an interwoven layer of hyaline, thick-walled generative hyphae, cylindrical, flexuose, with rounded terminal elements, coalescing perpendicular to pileus surface in places, forming interwoven erect bristle formations up to 1300 μm; gloeoplerous hyphae arising from context and terminating in surface layer, to half-way up bristles, as pileocystidia, widening to 7–10 μm toward apex, apex rounded to slightly inflated. Subpellis of roughly parallel thick-walled generative hyphae with bands of reddish-brown pigment. Stipitipellis like pileipellis with thicker interwoven hyaline surface layer, bristles up to 2000 μm. Stipe context like pileus context. Basidia (15–)20–30(–34) × (4–)5–7(–8) μm, narrowly clavate to clavate, 2–4 μm wide at base, 4-spored; sterigmata 3–5 μm long, 1–1.5 μm wide at base, tapering toward tip. Basidiospores (4.5–)5.0–7.0 ×4.0–6.0 μm (60/6), means 5.45–5.75–6.18 × 4.37–4.73–4.95 μm, Q: 1.00–1.38(–1.46), means 1.12–1.22–1.27, globose to ellipsoid, ornamentation finely verrucose, amyloid, apiculus to 1 μm. Pleurogloeocystidia (5–)8–10 μm wide, cylindrical to clavate, apex rounded to subcapitate, originating from parallel gloeoplerous hyphae in the spine context, often with abrupt right-angled bend, sometimes with bump near bend, or rarely branching without septa, arising parallel with basidia and terminating above hymenium, 30–60 μm long from bend to apex. Cheilogloeocystidia of similar size and shape, mostly without abrupt bend, also originating from parallel gloeoplerous hyphae in the spine context and extending conspicuously beyond basidia at spine apex.

Specimens examined: AUSTRALIA, VICTORIA: Blackwood, Jack Cann Reserve, 3 July 2005, Field Naturalists Club of Victoria Fungi Group 11 (MEL 2524519); Blackwood, Jack Cann Reserve, 2 July 2006, Field Naturalists Club of Victoria Fungi Group 55 (MEL 2305170); Blackwood, Jack Cann Reserve, 1 July 2007, Field Naturalists Club of Victoria Fungi Group 69 (MEL 2323326); Macedon, Lagoon Park, 27 August 2022, T.W. May 2142 (MEL 2524894); Gembrook, Kurth Kiln Regional Park, Shortcut Track, 30 August 2022, L.J. Vaughan 2, T.W. May & R. Richter (MEL 2524521); Gembrook, Kurth Kiln Regional Park, Scout Loop Track, 30 August 2022, L.J. Vaughan 3, T.W. May, R. Richter (MEL 2524522).

Figure 3 Microscopic features of Auriscalpium greyorum. a–c,e–i in 5% KOH; d in Melzer's reagent.

Diagnostic features. Auriscalpium greyorum is distinctive because of the combination of the habit on the trunk of living stringybark eucalyptus, the reduced stipe, the base of which is embedded in bark, and the small sporing bodies that are eventually dark brown with a hispid to appressed fibrillose surface.

Distribution & habitat. Found in Victoria in mixed Eucalyptus forest with Eucalyptus obliqua, E. radiata and E. viminalis and understory of species of Acacia, Banksia, Olearia, Pomaderris, Pteridium esculentum and grasses. Occurring from single sporing bodies to large colonies on the bark of living E. radiata, between 1–6 metres above ground, long-lived, persistent on tree from April–October.

Conservation status. This species was assessed as Endangered for the IUCN Red List of Threatened Species in 2019 based on an estimated population size of less than 250 mature individuals (May 2019). At that time it was known from only two sites, the type locality at Blackwood and at Olinda######, and at each site it was present on a single tree. It has since been found at several more sites in Victoria including in the Dandenong Ranges and at Lagoon Park, South of Woodend (#########). However, the population is highly fragmented. Threats to A. greyorum include fire and disturbance. In particular, it is unclear how A. greyorum responds to fire, which is a natural occurrence in eucalpyt forests. Some of the sites are close to motor- and mountain bike trails and sites where they are at risk of disturbance.

Etymology. Named in honour of Ed and Pat Grey, who have made significant contributions to the knowledge of Australian fungi, including recognition of the distinctiveness and rarity of this species which was first collected in 2005 by Ed and Pat during an excusion of the Field Naturalists Club of Victoria Fungi Group.

Notes.

In Victorian habitats, Auriscalpium greyorum is superficially morphologically similar to Pseudohydnum gelatinosum (Scop.) P. Karst. in the broad sense and Beenakia dacostae D.A.Reid, which are both small, hydnoid fungi that may grow on bark of trees in Eucalyptus forests. However, A. greyorum is easily differentiated from P. gelatinosum because it lacks a gelatinous texture, the pileus is smaller and dark brown, and the pendant spines are up to 4 mm long compared to 1 mm long in P. gelatinosum (Zhou et al. 2022; ####Other reference specifically for this species in Australia?). Beenakia dacostae is similar in size and general morphology to A. greyorum but typically has a more conspicuous stipe and a pale pileus, and is found growing on trunks of Dicksonia antarctica or on the soil under logs rather than on standing Eucalyptus. Microscopically, the amyloid spores separate A. greyorum from both P. gelatinosum and B. dacostae (Reid 1955; Zhou et al. 2022).

Auriscalpium greyorum is highly distinctive among species of the genus Auriscalpium because it lacks a conspicuous stipe, and Auriscalpium has historically included only stipitate species [with hydnoid basidiomes, gloeoplerous hyphae, and amyloid, ornamented spores]. The genus Gloiodon P.Karst. [also includes species with hydnoid basidiomes, gloeoplerous hyphae, and amyloid, ornamented spores but] strictly includes stemless or pileate-sessile or effused reflexed species. Several authors have discussed the morphological similarity of Auriscalpium and Gloiodon, and phylogenetic analyses of ITS and LSU regions support that Gloiodon is nested within Auriscalpium and requires taxonomic revision (Koski-Kotiranta & Niemelä 1987; Larsson & Larsson 2003).

Auriscalpium greyorum is morphologically most similar to Gloiodon nigrescens (Petch) Maas Geest., particularly the collection from Bali, Indonesia, documented by Desjardin and Ryvarden (2003). This is the only Gloiodon species known from the southern hemisphere and the specimen from Bali is the only collection with a publicly available sequence (GenBank: AF506450). This sequence was not included in the ITS phylogeny because it contains only partial 5.8S, complete ITS2 and partial 28S. Gloiodon nigrescens differs from A. greyorum with a growth habit on dead hardwoods, a deeply incised, digitiform margin, distinctly shorter spines, and smaller spores (Desjardin & Ryvarden 2003).

In the phylogenetic tree based on ITS sequences (Fig. 1), Auriscalpium greyorum is sister to a clade containing Auriscalpium barbatum from Western Australia and an undescribed Auriscalpium sp. from New Caledonia, Auriscalpium sp. NC-1, with percent identity of 90.02–91.45% and 90.38–91.33% respectively to Auriscalpium greyorum. Basal to this clade are two sequences of Auriscalpium sp. Aus 1, an undescribed Auriscalpium from Victoria with percent identity of 90.48–91.30% to A. greyorum. The most genetically similar species to Auriscalpium greyorum based on available sequence data is Auriscalpium sp. Aus 1. This taxon is morphologically easily distinguished from Auriscalpium greyorum because is has a stipe and is found growing on the ground amongst charcoal.