Thelidium sallaense Pykaelae & Myllys, 2023

Pykaelae, Juha, Kantelinen, Annina & Myllys, Leena, 2023, Taxonomy of Thelidium auruntii and T. incavatum complexes (lichenized Ascomycota, Verrucariales) in Finland, MycoKeys 96, pp. 1-23 : 1

Thelidium sallaense Pykaelae & Myllys sp. nov.

Figs 2E , 3F, G

Diagnosis.

Species morphologically rather similar to T. auruntii , but the thalli may be more brown-pigmented.

Type material.

Holotype. Finland, Koillismaa, Salla, Oulanka National Park, Savilampi 1,4 km NE, shore of Savinajoki river, river shore, on dolomite stone, 185 m a.s.l., 66°26'N, 29°11'E, 23 August 2011, J. Pykälä 44902 (H9220340, GenBank accession number: OP901878).

Description.

Prothallus not visible. Thallus pale brown to medium brown, rimose, algal cells c. 5-8 μm. Perithecia 0.21-0.28 mm in diam., 3/4(-1)-immersed in thallus, not leaving pits; c. 60-80 perithecia / cm2. Ostiole brown, plane to depressed, c. 20-60 μm wide. Involucrellum apical, c. 40-50 μm thick, slightly diverging from the exciple. Exciple c. 0.16-0.27 mm, wall pale to brown, K+ olive. Periphysoids c. 20-30 × 2 μm. Asci c. 67-83 × 25-32 μm, 8-spored. Ascospores (0-)1-septate, (26.3-)27.3-28.8-30.2(-31.1) × (12.0-)12.2-12.6-12.9(-13.4) μm (n = 12), perispore 1 μm thick present in some spores.

Habitat and distribution.

The species is only known from the type locality growing on dolomite stone on a rivershore. The species is likely to be very rare and threatened in Finland.

Etymology.

The name is according to the parish Salla from where the only known specimen has been collected.

Notes.

More material is needed to solve whether the species can be morphologically separated from T. auruntii . It may differ from T. auruntii by a more clearly brown pigmented thallus.

Figures

Figure 2. A Thelidium declivum (holotype) B T. huuskonenii (holotype) C T. mendax (holotype) D T. pseudoauruntii (holotype) E T. sallaense (holotype) F T. toskalharjiense (holotype). Scale bars: 1 mm (A-C, E, F); 0.5 mm (D).

Figure 3. Drawn anatomical features of the newly described Thelidium species. Represented perithecial features are similar between T. huuskonenii and T. toskalharjiense, as well as between T. declivum and T. mendax; therefore, they are shown combined. Spores are represented as intermediate size for all species A perithecia of T. huuskonenii and T. toskalharjiense combined B spores of T. huuskonenii C spores of T. toskalharjiense D perithecium of T. pseudoauruntii E spores of T. pseudoauruntii F perithecium of T. sallaense G spores of T. sallaense H perithecia of T. declivum and T. mendax combined I spores of T. declivum J spores of T. mendax. Scale bars for perithecia are 100 μm, and for spores 20 μm. Illustration: A. Kantelinen