Abrothallus altoandinus Flakus, Etayo & Rodr. Flakus, sp. nov.

Index Fungorum number: IF 900419; MycoBank number: MB 900419; Facesoffungi number: FoF 14174; Fig. 1

Etymology – The epithet refers to the habitat of the new species connected to the higher elevations of the Andes.

Diagnosis – The new species differs from Abrothallus usneae in having smaller ascomata (0.1–0.35 mm in diam.) and larger, slightly curved ascospores, composed of unequal cells, with the lower ascospore cell much thinner than the upper one.

Lichenicolous. Sexual morph: Mycelium immersed, indistinct, I–, K/I–. Ascomata apothecioid, superficial, developing directly on the host thallus, black, epruinose, strongly convex, sometimes tuberculate (when mature), strongly constricted at the base, 0.1–0.35 mm in diam., up to 250 μm tall. Epihymenium 5–10 µm, dark brown with additional violet pigment, K+emerald greenish, N+greyish. Exciple strongly reduced, of few layers of isodiametric to elongated cells, hyaline to pale brown. Hymenium 40–65 μm high, hyaline to violet in the upper part, K+emerald green. Interascal filaments irregularly branched and sometimes anastomosed, 1–2(–3) μm wide, apical cells slightly widened (up to 5–6 μm wide), brown pigmented. Hypothecium 60–80 μm high, pale to dark brown composed of large isodiametric cells forming a paraplectenchymatic tissue. Asci 30–60×7–22 μm, bitunicate, (4)8-spored, I–, K/I–, broadly clavate, apically widened with evident apical dome. Ascospores 1-septated, medium to dark brown, distinctly verrucose, covered by gelatinous cover (especially when younger), narrowly ellipsoid, usually slightly curved, 11–(x=15.1±1.5)–19 × 4–(x=5.2±0.7)–7 μm, l/b ratio 2–(x=3±0.5)–4.2 μm (n=102), not braking in semi-spores, composed of unequal cells, the lower cell much thinner [(2–)2.5–4(–4.5) µm] than the upper one, slightly constricted near the septum. Asexual morph: Undetermined.

Material examined: Bolivia, Department Cochabamba, Tiraque Province, Parque Nacional Carrasco, the crossroad below Cerro Juno, 17° 19′ 50″ S, 65° 43′ 50″ W, 4126 m, open high Andean vegetation, on saxicolous Usnea durietzii, 29 November 2014, A. Flakus 25,948 (KRAM-L 73246, holotype; LPB isotype).

Hosts and distribution: The species occur in Bolivia in the high Andean vegetation where is parasitizing an endemic lichen-forming fungus Usnea duriezii growing on siliceous rocks. Ascomata are developed on the main branches and laciniae of Usnea and not change the colour of the host thallus.

GenBank numbers: – ITS: OR116440

Notes: – Our phylogenetic analyses of combined LSU, ITS, SSU and tef1-α loci (Fig. 2) revealed that our collection (KRAM-L 73246) is not related to Abrothallus usneae s. str., described from Europe and the Portugal specimen described by Pérez-Ortega et al. (2014) has been included into the phylogenetic analyses. Our collection is a parasite on Usnea durietzii (Parmeliaceae, Lecanorales). The phylogenetic position of our collection is highly supported within the clade represented by species of Abrothallus growing on lichens of the order Peltigerales such as Erioderma, Lobaria, Nephroma, Pseudocyphellaria and Sticta (Suija et al. 2015). Our collection is characterized by medium sized, slightly curved ascospores with unequal cells (the lower cell is much larger and thinner than the upper one), 8-spored asci, the presence of violet pigment in ascomata (K +emerald greenish, N +greyish). Diederich (2003) was illustrated the similar shaped ascospores to our collection for A. pezizicola which is described from North America on Cladonia peziziformis. However, A. pezizicola can be easily distinguished by its different host preferences, yellowish pruinose
apothecia, olivaceous-green to almost black epihymenium (K+olivaceous, N+brown), and much smaller ascospores (6.5–9×2–3 µm) (Diederich 2003).

Figure 1 – Abrothallus altoandinus (KRAM-L 73246, holotype). a–c Habit of ascomata growing on Usnea durietzii. d–e Transversal section of ascoma (mounted in LPCB). f Strongly reduced exciple (mounted in LPCB). g Asci mounted in Lugol’s solution pretreated by 10% KOH (two left) and mounted in LPCB (right one). h Ascospores mounted in distilled water. i Ascospores mounted in LPCB. j Ascospores mounted in 10% KOH. Scale bars: a–b=250 µm, c=500 µm, d–e=50 µm, f=25 µm, g–j=10 µm

Figure 2 – Phylogenetic reconstruction of the systematic position of Abrothallus altoandinus and A. tetrasporus inferred from BI analyses of combined dataset of LSU, ITS, SSU and tef-α dataset. Bold branches represent either bootstrap values≥than 70 and/or Bayesian posterior probabilities≥than 0.95