OCELLOMMA ¹²

Gintaras Kantvilas ³

Ocellomma Ertz & Tehler, in D. Ertz et al., Fungal Diversity 70: 45 (2015).

Type: O. picconianum (Bagl.) Ertz & Tehler

Thallus crustose, ecorticate, lacking a prothallus. Photobiont trentepohlioid, with cells irregularly roundish, 10–20 µm diam. Ascomata apothecia, roundish, pseudolecanorine, erumpent, mostly broadly adnate to sessile. Disc black, white-pruinose. Thalline margin thin, exfoliating and ragged, white-pruinose, lacking algal cells, containing crystals of calcium oxalate. Proper exciple thin and poorly developed. Hypothecium hyaline to dark brown. Hymenium hyaline, not inspersed, hemiamyloid, KI+ pale blue, overlain by a brownish, crystalline, K+ olive epithecial layer. Asci cylindrical, 8-spored, of the myrticola-type: tholus weakly KI+ pale blue except for a thin, darker staining internal cap; ocular chamber short and blunt. Paraphysoids sparsely branched and anastomosed, slender, rather conglutinated in water and K; apices slightly expanded. Ascospores transversely 3-septate, hyaline, fusiform, mostly attenuated at the distal end, non-halonate; locules ± cylindrical. Conidiomata pycnidia, immersed. Conidia bacilliform, straight or curved. Chemistry: roccellic acid recorded in one species.

A genus of two corticolous or lignicolous species, widely distributed in coastal, remnant vegetation with an essentially Mediterranean climate. It was segregated from Schismatomma by Ertz et al. (2015) chiefly on the basis of molecular data. The two genera have identical, myrticola-type asci and 3-septate ascospores. Schismatomma differs by having irregularly roundish to elongate or stellate apothecia with a better developed thalline margin, and its spores tend to be acicular-fusiform. In Tasmania, Ocellomma is more likely to be mistaken for a species of Lecanographa, which has grumulosa-type asci and halonate ascospores, or Lecanactis, which has abietina-type asci.

Key references: Ertz et al. (2015); Kantvilas et al. (2020).

1 Ocellomma rediuntum (Stizenb. ex Hasse) Kantvilas, Gueidan & Tehler

Lichenologist 52: 188 (2020); —Lecanora rediunta Stizenb. ex Hasse, Bull. Torrey Bot. Club 24: 446 (1897); Dirina rediunta (Stizenb. ex Hasse) Zahlbr., Ann. Naturhist. Mus. Wien 16: 82 (1901); Schismatomma rediunta (Stizenb. ex Hasse) Tehler, Lichenologist 17: 211 (1985).

Thallus scurfy, pale grey-white, 80–100 µm thick, rather patchy and uneven. Apothecia 0.2–0.5 mm wide, scattered; thalline margin 10–15(–25) µm thick, at length becoming ± excluded, in section dark brown at the outer edge, paler and KI– within; disc plane at first, becoming convex. Hypothecium 40–60(–90) µm thick, dark reddish brown, K+ olive, sometimes paler and patchily KI+ pale violet in the upper part. Hymenium 60–80 µm thick; asci 50–65 × 13–20 µm; paraphysoids 1–1.5 µm thick, with apices minutely spinulose, 2–2.5 µm thick. Ascospores (16–)17–20.9–25 × 4–4.6–5.5 µm; wall 0.5–1 µm thick. Conidia 5–7 × 1–1.5 µm.

Chemistry: nil.

This species has a remarkably disjunct world distribution, ranging from remnant coastal vegetation in California and on Kangaroo Island (South Australia) to the trunk of an exotic palm in the Royal Botanic Gardens in Melbourne (Kantvilas et al. 2020). In Tasmania, it is known from several, widely scattered localities that include a similarly diverse range of habitats, including Callitris rhomboidea-dominated relict woodland on the East Coast, coastal Melaleuca ericifolia-dominated swamp woodland and a large, exotic Sequoia in a public park. The conspecificity of these populations has been confirmed by DNA studies. Ocellomma rediuntum tends to favour somewhat drier, sheltered microhabitats on the oldest, largest trees. In the Tasmanian flora, it is superficially most similar to species of Lecanactis, although these tend to occur in wetter, cooler areas and have a markedly different apothecial anatomy.

Wind Song Property, 42°21’S 147°55’E, 40 m, 2017, G. Kantvilas 392/17 (BM, CANB, FH, HO, S); southern end of Musselroe Bay, 40°48'36"S 148°06'41"E, sea-level, 2019, G. Kantvilas 243/19 (CANB, HO); Westbury Green, 41°32’S 146°50’E, 170 m, 2021, G. Kantvilas 50/21 (HO).

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