Astrothelium isidiatum Kukwa, Flakus & Rodr. Flakus, 2023

Kukwa, Martin, Rodriguez-Flakus, Pamela, Aptroot, Andre & Flakus, Adam, 2023, Two new species of Astrothelium from Sud Yungas in Bolivia and the first discovery of vegetative propagules in the family Trypetheliaceae (lichen-forming Dothideomycetes, Ascomycota), MycoKeys 95, pp. 83-100 : 83

Astrothelium isidiatum Kukwa, Flakus & Rodr. Flakus sp. nov.

Fig. 3

Diagnosis.

The new species differs from all known species of the genus by developing groups of isidia on the surface of areoles, which break off to reveal a medulla that resembles soralia.

Type.

Bolivia. Dept. La Paz; Prov. Sud Yungas, near Reserva Ecolo ́gica de Apa Apa, Sanani near Chulumani , 16°20'39.70"S, 67°29'54.32"W, elev. 2423 m, Yungas montane forest, corticolous, 23 Jan 2020, A. Flakus 30000 & P. Rodriguez-Flakus (KRAM-L 73245 holotype; LPB, UGDA isotypes) .

Description.

Thallus endosubstratal to episubstratal and then grey-green, shiny, folded in non-areolate parts, with areoles, isidiate. Areoles tuberculate, sometimes with cylindrical outgrowth developing at the lateral parts of areoles (Fig. 3C ), constricted at the base (especially when young) or not, rounded to elongate and up to 1.2 mm wide. Isidia mostly cylindrical, globose when young, simple, rarely branched, constricted at the base or not, developing on areoles, up to 0.5 mm long and 0.2 mm wide, often shed from areoles and then exposing the yellow medulla of areoles, which then resemble soralia; sometimes elongated isidia-like outgrowth developing directly from the endosubstratal thallus present (Fig. 3D ). Cortex up to 30-50 µm in width, of two layers, lower part prosoplectenchymatous and visible mostly in young areoles and upper part gelatinous. Photobiont layer up to 35 µm wide. Medulla whitish (only in young areoles) to yellow, densely filled with rhomboid or irregular crystals (crystals not dissolving in K), crystals 4-35 × 3-12 µm. The upper layer of areoles with shed isidia pseudoparenchymatous. Ascomata and pycnidia unknown.

Chemistry.

Thallus surface UV-, K-, C-, KC-; medulla with yellow pigment, K+ yellow going into solution, C+ yellow-orange; upper parts of areoles with shed isidia with patches of orange pigment reacting K+ purple. Unidentified substances (probably some of them are anthraquinones) in trace to minor amounts detected by thin layer chromatography.

Etymology.

The name refers to the production of isidia, which are unique in the genus.

Distribution and habitat.

So far, the species is known only from the type locality in the Yungas forest in Bolivia.

Notes.

This is a very characteristic species with areoles filled with crystals, cylindrical isidia developing on the areoles and usually yellow thallus medulla. The ascomata were not found in the studied material. It differs from all species of Astrothelium and Trypetheliaceae in the presence of isidia.

Some species of Trypetheliaceae , for example, Architrypethelium lauropaluanum Lücking, M. P. Nelsen & Marcelli, Astrothelium komposchii Aptroot or A. puiggarii ( Müll. Arg.) Aptroot & Lücking ( Aptroot and Lücking 2016; Aptroot et al. 2016c; Lücking et al. 2016b), develop thalli with areoles resembling isidia which somehow are similar to these of A. isidiatum (Fig. 3C, D ). However, A. isidiatum differs by developing cylindrical and often constricted at the base isidia which are covering the entire areoles (Fig. 3A, B ). The isidia are easily broken and shed from areoles revealing the medulla of areoles that then resemble soralia.

We are not aware of any other similar species in other groups, which remind us of the unique taxon described here.

Figures

Figure 3. Astrothelium isidiatum (type collection) A-D thallus morphology A, B isidia developing in groups on areoles which are partly shed exposing the medulla of the areoles C isidia-like outgrows developing on lateral parts of areoles D isidia-like outgrowths developing directly from the endosubstratal parts of the thallus E, F a vertical cross-section through thallus with crystals present in the medulla (E) (in LPCB) G, H vertical cross-section through cortical layer (in LPCB). Scale bars: 1000 μm (A, B); 500 μm (C, D); 50 μm (E, F); 10 μm (G, H).