THALLOIDIMA ¹

Gintaras Kantvilas ²

Thalloidima A.Massal., Ric. Auton. Lich. Crost.: 95 (1852).

Type: T. candidum (Weber) A.Massal.

Thallus squamulose or sometimes absent in non-lichenised, lichenicolous species, usually with a cortex and epinecral layer, commonly pruinose with calcium oxalate present; pores lacking; pseudocyphellae sometimes present, punctiform or linear; isidia or soredia absent. Photobiont a unicellular green alga with ± globose cells 6–15 µm diam. Ascomata apothecia, biatorine, sessile, basally constricted, with calcium oxalate present in some species. Disc plane to convex, black, sometimes pruinose. Proper exciple persistent or soon excluded, concolorous with the disc, in section annular, externally pigmented greenish grey, K+ violet, C+ violet, N+ violet, internally hyaline or diffusely pigmented, composed of radiating, branched, thick-walled hyphae. Hypothecium hyaline to dark brown. Hymenium hyaline, overlain by a greenish grey, K+ violet, C+ violet, N+ violet epithecium. Paraphyses sparingly branched, 2–2.5 µm thick; apices distinctly capitate, to 4–6 µm wide, with a gelatinous, pigmented outer cap. Asci clavate, 8-spored, of the Bacidia-type: tholus well-developed, amyloid, with a weakly amyloid, conical masse axiale and a short, conical ocular chamber. Ascospores 1–3-septate, hyaline, ellipsoid, bacilliform or fusiform, rarely acicular, non-halonate, thin-walled. Conidiomata pycnidia, rare, immersed. Conidia filiform. Chemistry: containing no substances of taxonomic significance identifiable by TLC.

Like Bibbya and Toniniopsis, Thalloidima is a segregate of the large, heterogenous genus Toninia, and has been distinguished mainly on the basis of DNA-sequence data (Kistenich et al., 2018). It differs from the latter morphologically chiefly by having an internally unpigmented exciple and, critically, by containing the pigment sedifolia-grey in the epithecium (greenish grey, K+ violet, C+ violet, N+ violet). The genus includes about 10 species, found on soil and stones, mostly in temperate or Mediterranean environments of the Northern Hemisphere; two species, including the widespread T. sedifolium (Scop.) Kistenich et al., have been recorded for the Australian mainland. Most species have a squamulose thallus but at least two are non-lichenised and occur as parasites on cyanophilic lichens.

1 Thalloidima ioen (Herre) S.Ekman & Timdal

Taxon 67: 896 (2018);—Bacidia ioessa Herre, Proc. Washington Acad. Sci. 12: 98 (1910).

Thallus squamulose; squamules scattered or contiguous, dull olive-brown, epruinose but with whitish abraded areas, irregular, rather gnarled and unevenly convex, 0.5–2 wide, without pseudocyphellae; calcium oxalate lacking. Apothecia 0.4–1 mm diam., scattered or crowded together, fused and deformed, epruinose, lacking calcium oxalate; disc black to grey-black, plane at first, becoming convex; proper exciple black, persistent or becoming inapparent and excluded in more convex apothecia, in section 45–70 µm thick, greenish grey, K+ violet at the outer edge, hyaline or diffusely greenish grey within. Hypothecium 120–180 µm thick, pale in the lowermost part, pale straw-coloured, K± pale yellowish above. Hymenium 60–70 µm thick, overlain by greenish grey epithecium, K+ violet, C+ violet, N+ violet; asci 45–55 × 12–16 µm. Ascospores 3-septate, bacilliform to fusiform, (18–)19–22.0–26 × 3–3.7–4.5 µm.

Known from the south-west of North America and in South America, with an outlying record from the Kimberley region of Western Australia (reported under its synonym Toninia submexicana de Lesd.). The identification of specimens from Tasmania, where the species is rare, remains tentative pending a wider study and further collections. It is known from dolerite-derived soil at mid-elevations in the east, and is recognised by the squamulose thallus, the apothecia with a hyaline hypothecium and sedifolia-grey epithecium, and the bacilliform to fusiform, 3-septate ascopores. Thalloidima sedifolium differs mainly by having 1-septate ascospores, 12–24 × 3–5 µm, and a dark coloured hypothecium (Timdal 1992).

St Patricks Head, 41°35’S 148°14’E, 1973, G.C. Bratt 73/664 (HO); Gunners Quoin summit, 42°46’S 147°20’E, 440 m, 1992, G. Kantvilas 181/92 & J.A. Elix (HO).

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