Heteroradulum australiense L.W. Zhou, Q.Z. Li & S.L. Liu, 2022

Li, Qian-Zhu, Liu, Shi-Liang, Wang, Xue-Wei, May, Tom W. & Zhou, Li-Wei, 2022, Redelimitation of Heteroradulum (Auriculariales, Basidiomycota) with H. australiense sp. nov., MycoKeys 86, pp. 87-101 : 87

Heteroradulum australiense L.W. Zhou, Q.Z. Li & S.L. Liu sp. nov.

Figures 2 , 3

Etymology.

australiense (Lat.), refers to Australia.

Type.

Australia, Tasmania, Tahune Adventures, Arve River Picnic Area , on fallen angiosperm branch, 15 May 2018, L.W. Zhou, LWZ 20180515-26 (holotype in MEL, isotype in HMAS) .

Diagnosis.

Heteroradulum australiense differs from other species in this genus by the generative hyphae having a mixture of simple septa and clamp connections.

Description.

Basidiomes annual, resupinate, adnate, without odor or taste when fresh, leathery, covering 24.5 cm in widest dimension and up to 0.4 mm thick. Hymenophore odontioid, covered by irregularly arranged spines, up to 0.2 mm long, 3-5 per mm, pale red to reddish lilac when fresh, pale orange to brownish gray upon drying. Margin smooth, adnate, yellowish white, 0.5 mm wide.

Hyphal system dimitic; generative hyphae with simple septa or clamp connections; skeletal hyphae IKI-, CB+; tissue unchanged in KOH. Subicular generative hyphae hyaline, thin to thick-walled, rarely branched, 2-4 μm in diam; skeletal hyphae hyaline to brownish, thick-walled, interwoven, occasionally branched, 2.5-4 μm in diam, sometimes irregularly inflated up to 6 μm. Subhymenial generative hyphae hyaline to brownish, thin-to slightly thick-walled, 2-3.5 μm in diam; skeletal hyphae brownish, thick-walled, encrusted by grainy crystals, subparallel and vertical along substrate, compact, 2-4.5 μm in diam. Clavate to subcylindrical cystidia abundant, septate with or without clamp connections, thin-walled, 24-56 × 3-8 μm. Skeletocystidia present as endings of subicular skeletal hyphae, distinctly thick-walled, heavily encrusted by grainy crystals, 4-7 μm in diam. Dendrohyphidia abundant, scattered among hymenial cells, covering the hymenial surface, branched, up to 54 μm long, 2-3 μm in diam. Basidia narrowly ovoid to obconical, longitudinally septate, four-celled, 29-34.5 × 10-13.5 μm, with enucleate stalk up to 14 × 4 μm. Basidiospores cylindrical, slightly or distinctly curved, hyaline, thin-walled, smooth, occasionally with oily inclusions, IKI-, CB-, (14.5-)15-20(-20.5) × 5-7(-7.5) μm, L = 17.0 μm, W = 6.2 μm, Q = 2.66-2.88 (n = 90/3).

Specimens (paratypes) examined.

Australia, Victoria, Yarra Ranges National Park, Dandenong Ranges Botanic Garden, on a fallen branch of Eucalyptus , 12 May 2018, L.W. Zhou, LWZ 20180512-20 (HMAS), on fallen angiosperm branch, 12 May 2018, L.W. Zhou, LWZ 20180512-25 (HMAS).

Remarks.

Heteroradulum australiense is characterized by pale red to reddish lilac basidiomes, a dimitic hyphal system, generative hyphae with simple septa or clamp connections, abundant skeletocystidia in the hymenium, and basidia with an enucleate stalk. Heteroradulum kmetii and H. spinulosum resemble H. australiense by odontoid hymenophores, a dimitic hyphal system and the presence of skeletocystidia ( Malysheva and Spirin 2017). However, H. kmetii has longer spines (up to 1 mm long) and slightly larger basidiospores (14.3-22.3 × 6-9.2 μm), and generative hyphae always with clamp connections; and H. spinulosum differs by basidia with a shorter enucleate stalk (up to 6 μm long) and generative hyphae always with clamp connections ( Malysheva and Spirin 2017).

In regard to previously described Australian species against which H. australiense should be compared, the coriaceous, resupinate species of the Auriculariales are poorly sampled from Australia. May et al. (2003) listed records from Australia of a number of species of Eichleriella , Exidiopsis and Heterochaete that were originally described from the Northern Hemisphere. Such records remain suspect unless confirmed. Only two new species have been described on the basis of type materials from Australia that may fall within these three genera: Heterochaete cheesmanii Wakef. and Irpex depauperatus Massee.

Heterochaete cheesmanii was described by Wakefield (1915) from a collection on wood from New South Wales, characterized by the thin, orbicular basidiomes with a shortly reflexed margin, the pale hymenium with sparse, minute spines, the soft fulvous context, with 4-spored, cruciate basidia 15 × 10-12 μm, and curved, cylindrical spores, 14-15 × 5-5.5 μm, and hyphae 1.5-4 μm diameter. Reid (1957) examined the type at K and noted the presence of "conspicuous branched paraphyses". Heterochaete cheesmanii differs from H. australiense by the shorter basidiospores. It will be necessary to obtain sequences from H. cheesmanii to ascertain its correct generic placement, but it could well be a member of Heteroradulum .

Irpex depauperatus was introduced by Massee (1901) with a short description, based on a collection on dead bark by Rodway from Tasmania. Note that due to existence of the previously described Irpex depauperatus Berk. & Broome, the replacement name Irpex tasmanicus Syd. & P. Syd. was introduced for I. depauperatus Massee. According to Massee (1901), Irpex depauperatus Massee was characterized by the tawny hymenium with short, laterally incised spines forming orbicular then confluent patches with a white edge and basidiospores of 6 × 3-4 μm. No comparison against other species was provided in the protologue. Both Bodman (1952) and Reid (1957) placed I. depauperatus as a synonym of other species. Without examining the type, Bodman (1952) listed I. depauperatus as a possible synonym of Heterochaete delicata (Klotzsch) Bres. However, Reid (1957) considered that I. depauperatus was a synonym of Eichleriella spinulosa (Berk. & M.A. Curtis) D.A. Reid (basionym Radulum spinulosum Berk. & M.A. Curtis, now accepted as Heteroradulum spinulosum ). Reid (1957) provided a description of E. spinulosa (with I. depauperatus listed as synonym) that is evidently based on the cited Australian specimen (Miller s.n., K, Herb. F.P.S.M. No. 4996). Despite the fact that Massee (1901) originally described I. depauperatus as having basidiospores of 6 × 3-4 μm, Reid (1957) found that the type at K has basidiospores of 19 × 7 μm, matching the basidiospores from the Australian collection by Miller in 1954, but he did not provide any further details of the characters of the type collection of I. depauperatus .

Irpex depauperatus potentially belongs in Heteroradulum but due to slight morphological differences between species such as H. australiense and H. spinulosum , and the potential for further species to occur in the region, DNA sequences would be ideal to assist in interpretation of the old name. However, it is unlikely to be able to readily obtain DNA from the more than 100-year old type of Irpex depauperatus , which is borne out by unsuccessful attempts to amplify ITS and LSU sequences from several Australian collections in MEL filed under Heterochaete , collected in the 1950s and 1960s. Collections for which DNA amplification was unsuccessful included MEL 2313650 (which is a duplicate of the K collection Miller s.n., Herb. F.P.S.M. No. 4996). The morphology of Miller s.n. as recorded by Reid (1957) matches H. australiense in basidiospore size and shape and presence of skeletocystidia. However, the connection between this collection and the type of Irpex depauperatus is not definite, as only basidiospore dimensions of the latter were provided by Reid (1957). It remains possible that Irpex tasmanicus (= I. depauperatus ) represents an earlier name for Heteroradulum australiense . Given the lack of a sequence from the type and the meagre morphological details available, we choose to introduce a new species, well-characterized by the combination of morphology and sequence data. Perhaps with the application of next generation sequencing, it may become possible to recover sequences from older types more routinely as has been done already in some cases, such as by Delgat et al. (2019).

Figures

Figure 2. Basidiomes of Heteroradulum australiense. A-B LWZ 20180515 - 26 (holotype) C LWZ 20180512 - 20 (paratype) D LWZ 20180512 - 25 (paratype). Scale bars: 2 mm (A); 1 cm (B-D).

Figure 3. Microscopic structures of Heteroradulum australiense (drawn from the holotype, LWZ 20180515 - 26). A basidiospores B, C basidia and basidioles D cystidia E skeletocystidia F dendrohyphidia G hymenium H subicular hyphae. Scale bars: 10 μm (A-H).