Rossbeevera pachydermis (Zeller & C.W. Dodge) T. Lebel, in Lebel et al., Fungal Diversity 52(1): 54 + 73 (2012)
Basidiomata hypogeal to often emergent, solitary or caespitose, (12–) 20–50 mm diameter, tuberiform, pyriform or subglobose, smooth to roughened with exposure, sometimes cracking, from off-white to yellow ochre to brilliant iodine greenish-blue in large patches, not cyanescent when bruised, drying pallid ferruginous. Pileus well developed, 1–2 mm thick, white or cream coloured in section, not cyanescing. Hymenophore initially off-white becoming rusty dark brown to chocolate brown at maturity, firm to rubbery, loculate, chambers fine, 2–3 to 1 mm, gelfilled. Stipe-columella reduced to a few narrow branches arising from a small, 2–6 mm wide×2–3 mm high, inserted sterile basal pad, white to translucent, cartilaginous, more conspicuous in immature sporocarps. Odour strongly earthy and slightly of bleach.
Basidiospores (10.5–) 11–14 (−15)×(6–) 8–10 μm, (mean 13.2×8.3 μm), Q=1.38–1.61; ellipsoid to short fusoid, golden brown to brown in KOH, with a thickened wall, apex bluntly pointed, with 4–5 longitudinal ridges, 1.5–3 μm tall, which are rounded or with a wavy edge, and spiraling slightly on some spores. Basidia 14–21×6– 13 μm, cylindrical to clavate, 4-spored; basidioles 10– 15×5–11 μm, clavate to broadly clavate. Hymenial cystidia absent. Subhymenium poorly developed. Hymenophoral trama broad, 150–325 μm thick, of gelatinized, interwoven hyaline hyphae, 3–9 μm diam. Peridiopellis a narrow 50–75 μm thick, repent epicutis, of subparallel or partially interwoven hyaline, subgelatinised thin-walled hyphae, 3–9 μm diam., which become yellow in 3% KOH, with scattered slightly inflated hyphal elements, 5– 13 μm diam.; overlying a broad context, up to 1200 μm thick, of interwoven gelatinised hyaline hyphae 3–6 μm diam.
Habitat, distribution and season: Hypogeal or more often emergent, in beech (Nothofagus fusca, N. solandrii and N. menziesii) forest. New Zealand. February–October.
Index fungorum number: IF547272
Notes: Rossbeevera pachydermis is restricted in distribution to New Zealand, and differs from other Australasian species in the non-cyanescent, greenish-blue pileus, generally larger emergent sporocarps, more deeply coloured spores, and the much broader pileus and hymenophoral trama. In our examination of type material and recent collections, the structure of the pileus was found to be consistently hyphal with some scattered inflated elements, but never pseudoparenchymatous as described in the protologue of Hymenogaster pachydermis (Zeller and Dodge 1934). Analyses of DNA did not provide any support for differentiation of R. pachydermis from Australasian or Japanese taxa. The type of Hymenogaster pachydermis (NY) from Mt Dun, and one of the collections cited by Cunningham (1979) from Mt Reeves (PDD8334) are immature specimens of the species, the spores are shorter and the ornamentation not as high or robust, and paler in colour. The Australian collection placed under this name by Beaton et al. (1985) is a specimen of R. vittatispora. The Zeller 2260 collection from the USA listed in Beaton et al. (1985) is a Chamonixia sp., with broadly ellipsoid spores that have 8 distinct ridges. All material of Rossbeevera pachyderma examined occurred in association with the three main species of Nothofagus found in New Zealand. Nothofagus species occur on a range of soil types, and altitudinal zones, from the coast to sub-alpine areas; as such R. pachydermis appears to have a broad ecological requirement.
Figure 1. Bayesian 50% majority rule consensus topology based on nuclear LSU rDNA dataset of 66 sequences. Bayesian posterior probabilities (pp) are indicated above or below branches at nodes
Figure 2. Bayesian 50% majority rule consensus topology based on nuclear ITS1–5.8S–ITS2 rDNA dataset of 55 sequences. Bayesian posterior probabilities (pp) are indicated above or below branches at nodes