Thelidium huuskonenii 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 huuskonenii Pykaelae & Myllys sp. nov.

Figs 2B , 3A, B

Diagnosis.

Species morphologically rather similar to T. auruntii , but the spores smaller, perithecia often leaving deep pits, and the thallus predominantly endolithic.

Type material.

Holotype. Finland, Enontekiön Lappi, Enontekiö, Kilpisjärvi, Saana, fell, steep NE-slope, dolomite rock outcrop, on NE-facing wall, abundant, 820 m a.s.l, 69°02'N, 20°51'E, 11 August 2011, J. Pykälä 44167 (H9204900, GenBank accession number: OP901862).

Description.

Prothallus not visible. Thallus white to grey, endolithic to thinly epilithic, only surrounding perithecia, algal cells, c. 4-7 μm, in one specimen surrounded by one dark line. Perithecia 0.18-0.32 mm in diam., (1/2-)3/4-1-immersed, leaving shallow to deep pits; c. 80-120 perithecia / cm2. Ostiole pale to dark, plane to depressed, c. 20-40 μm wide. Involucrellum absent, apical or covering half of the exciple, 0-60 μm thick, appressed to the exciple or clearly diverging from it. Exciple 0.20-0.28 mm, wall dark brown to black, c. 15-20 μm thick, apex may be thickened to 50-80 μm thick. Periphysoids c. 20-45 × 1.5-2 μm, branching. Asci c. 58-74 × 22-25 μm, 8-spored. Ascospores (0-)1-septate, (16.4-)18.2-20.7-23.2(-27.6) × (8.0-)8.6-9.9-11.2(-14.4) μm (n = 69).

Habitat and distribution.

Four specimens have been confirmed by sequencing, but more than twenty morphologically similar specimens have been collected from the calcareous fells of Saana and Toskalharji. The species seems to occur only in northern Finland, in Enontekiö on fells on dolomite rock outcrops, boulders, stones and pebbles. It grows on southern and northern slopes and on rather flat surfaces. The altitudinal range is 705-890 m a.s.l.

Etymology.

The species is named after A.J.Huuskonen, the Finnish amateur lichenologist, who most intensively collected lichens from the Enontekiö area.

Notes.

The species differs from T. auruntii in smaller spores, perithecia often leaving deep pits and thinner, predominantly endolithic, thallus. The species has been previously reported from Finland as T. decussatum ( Pykälä 2010a). The Finnish specimens have similar perithecia and involucrellum as T. decussatum . However, T. decussatum ([Germany] Trier, 1862, Mezler, Rabenhorst Lichenes Europaei 646 (UPS!, syntype)) has a rimose thallus and the spores may be slightly larger (20-25 × 10-11 μm). Furthermore, the type locality is in a temperate zone in lowland Germany. Phytogeographically, it is unlikely that such species would occur only in fells in the northwestern most part of Finland. Thelidium stenosporum Servít (Slovakia: Bielské Tatry: in rup. calc. in convalle Dominův důl, … m. Havran … norg, 1700 m, 1937, Suza (PRM-858497!, syntype)) has smaller perithecia and narrower spores. Thelidium bubulcae (A.Massal.) Arnold (syntypes: VER, UPS-L-686416!)) has larger rimose to areolate thallus, larger perithecia (0.2-0.37 mm) and larger spores: 20-27 × 9-13 μm. Thelidium polycarpum Servít (Montenegro, Lovčen, Ljubin potok, 1230 m, 1929, Servít (PRM-858491!, holotype)) has smaller perithecia (0.13-0.23 mm) and spores (15-23 × 8-9 μm). Thelidium klementii Servít has rather thick rimose to areolate thallus and slightly larger spores and is only known from a temporarily inundated calcareous rock ( Thüs and Nascimbene 2008).

Other specimens examined.

Finland. Enontekiön Lappi, Enontekiö, Kilpisjärvi, Saana fell, Saana nature reserve , low arctic zone, on SW-facing wall of dolomite rock outcrop, 880 m a.s.l., 69°02'N, 20°51'E, 27 July 2007, J. Pykälä 31576 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dolomite rock outcrop, on S-slope, 730 m a.s.l, 69°12'N, 21°26'E, 2 August 2011, J. Pykälä 43243 (H); Enontekiö, Porojärvet, Toskalharji, Toskaljärvi N, fell, dolomite rock outcrop, on dolomite pebbles, 735 m a.s.l, 69°12'N, 21°26'E, 2 August 2011, J. Pykälä 43246 (H) .

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