Astrothelium chulumanense Flakus, Kukwa & Aptroot, 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 chulumanense Flakus, Kukwa & Aptroot sp. nov.

Fig. 2

Diagnosis.

Characterised by pseudostromata not differing in colour from the thallus, perithecia immersed for the most part in thallus, with the upper part elevated above the thallus and covered, except the tops, with orange pigment, apical and fused ostioles, the absence of lichexanthone, clear hamathecium, 8-spored asci and amyloid, large (125-167 × 27-35 μm), muriform ascospores with a thickened median septum.

Type.

Bolivia. Dept. La Paz; Prov. Sud Yungas, Pataloa, near estación biológica Santiago de Chirca, near Chulumani , 16°23'57.16"S, 67°34'33.96"W, elev. 2271 m, Yungas montane forest, corticolous, 22 Jan 2020, A. Flakus 29985 & P. Rodriguez-Flakus (holotype KRAM-L 73244, isotypes LPB, UGDA) .

Description.

Thallus corticate, with corticiform layer 10-20 μm thick, uneven, folded to bumpy, somewhat shiny, continuous, ca. 0.1mm thick, greenish, surrounded by a dark prothallus, not inducing swellings of the host bark, covering areas ≤ 8 cm diam. Pseudostromata with a surface similar to the thallus, distinctly raised above the thallus, hemispherical to wart-shaped, ca. 1.5-3 mm in diam. and 0.5-1.5 mm high, the same colour like thallus with black to orange-black apical spot, inside containing bark tissue. Ascomata perithecia, pyriform to hemispherical, aggregated, 0.6-1 mm diam., emerging from beneath the upper periderm layers of the bark and surrounded by bark tissues in outside part, immersed in most parts in regular in outline pseudostromata, upper part elevated above the thallus and covered, except the tops, with orange pigment. Ostioles apical, centrally fused to form a shared channel leading to various chambers. Wall fully carbonised, not differentiated into excipulum and involucrellum, thicker, ≤ ca. 100 μm wide in the upper part and thinner, up to ca. 20 μm wide, near the base. Ostioles apical, fused, black. Hamathecium clear, composed of thin and anastomosing paraphysoids, 1.5-2.5 μm wide. Asci 8-spored, 350-470 × 56-60 µm. Ascospores distoseptate, hyaline, I+ violet, densely muriform, with a gelatinous layer in younger stages, with a distinct thickened median septum, sometimes breaking into two parts in the septa, narrowly ellipsoid, 125-167 × 27-35 μm, ends rounded, lumina diamond-shaped.

Chemistry.

Thallus surface UV+ orange-yellow, K-, C-, KC-, thallus medulla K-; pseudostromata surface UV+ orange-yellow, K-, inner part of pseudostromata K-, visible part of perithecia K+ red. Trace of unidentified substance detected in the thallus by thin layer chromatography; pigment on the top of perithecia.

Etymology.

The species is named after its locus classicus located near Chulumani town in Bolivia.

Distribution and habitat.

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

Notes.

Astrothelium chulumanense can be distinguished by pseudostromata not differing in colour from the thallus, the orange-yellow reaction in UV (perhaps due to the presence of an unknown substance), the absence of lichexanthone, perithecia immersed for the most part in the thallus, but with upper part elevated above the thallus and covered, except the tops, with orange pigment, apical and fused ostioles, clear hamathecium, 8-spored asci and amyloid, large, muriform ascospores with median septa. The new species is phylogenetically related and externally similar to A. robustum . Both species have also ascomata with fused ostioles; however, ascospores in A. robustum are (3-)5-7(-9)-septate and I negative. Furthermore, the species does not produce secondary metabolites ( Aptroot and Lücking 2016; Aptroot 2021).

Only four Astrothelium species have clear hamathecium, 8-spored asci and large, muriform ascospores, which react I+ violet. Astrothelium amylosporum Flakus & Aptroot has pseudostromata not covered by thallus and lacks pigments, whereas A. palaeoexostemmatis Sipman & Aptroot lacks pigments, has smaller ascospores (85-100 × 20-24 μm) and ascomata are almost completely covered by the thallus and do not form distinct pseudostromata. Astrothelium sanguinarium (Malme) Aptroot & Lücking differs in the shape of pseudostromata, the pigment is red (isohypocrellin), reacts K+ yellow-green and is present internally within pseudostromata. Astrothelium sanguineoxanthum Aptroot has smaller (up to 86 μm long) ascospores, whitish pseudostromata and produces lichexanthone and isohypocrellin (internal in pseudostromata) ( Aptroot and Lücking 2016; Aptroot et al. 2016b, 2019; Flakus et al. 2016; Aptroot 2021).

Several other species of the genus have pseudostromata or aggregated ascomata often with fused ostioles, clear hymenium, large (at least some over 80 μm long) and muriform, but I negative ascospores and 8-spored asci. They differ significantly in other characters (for the key to all species, see Aptroot (2021)). In A. alboverrucum (Makhija & Patw.) Aptroot & Lücking, ascomata are solitary to diffusely pseudostromatic, prominent, with whitish surrounding the black ostiolar area ( Aptroot and Lücking 2016). Astrothelium carassense Lücking, M. P. Nelsen & Marcelli differs in perithecia completely immersed in pseudostromata, which are covered with orange pigment ( Lücking et al. 2016b). Astrothelium chapadense (Malme) Aptroot & Lücking differs in dark brown pseudostromata, up to 100 μm long ascospores and the lack of secondary metabolites ( Aptroot and Lücking 2016). Astrothelium confluens ( Müll. Arg.) Aptroot & Lücking has ascomata completely covered by the thallus and ascospores measuring ca. 130 × 20 μm ( Aptroot and Lücking 2016). Astrothelium defossum ( Müll. Arg.) Aptroot & Lücking has joined ascomata, which are dispersed to confluent or diffusely pseudostromatic with lichexanthone on the surface ( Aptroot and Lücking 2016). Astrothelium elixii Flakus & Aptroot develops white pruinose pseudostromata and produces lichexanthone and isohypocrellin (internal in pseudostromata) ( Flakus et al. 2016). Astrothelium flavoduplex Aptroot & M. Cáceres differs from the new species by the presence of lichexanthone, oval to irregular or reticulate in outline pseudostromata, which are yellow to brownish and contain up to 50 ascomata with no fused ostioles ( Aptroot and Cáceres 2016). Astrothelium flavomurisporum Aptroot & M. Cáceres has aggregated ascomata (but without pseudostroma) covered with the thallus, lumina of ascospores with yellow oil and lacks secondary metabolites ( Aptroot and Cáceres 2016). Astrothelium megeustomum Aptroot & Fraga Jr produces ascomata mostly immersed in the bark tissue below pseudostromata, up to 125 μm long ascospores and lichexanthone around ostiolar region ( Aptroot et al. 2016b). Astrothelium mesoduplex Aptroot & M. Cáceres has ascomata immersed in superficially yellow to orange, pale yellow inside pseudostromata and shorter, up to 100 μm long ascospores ( Aptroot and Cáceres 2016). Astrothelium octosporoides Aptroot & Lücking differs in solitary or a few grouped ascomata covered by the thallus and the lack of secondary metabolites ( Aptroot and Lücking 2016). Astrothelium purpurascens ( Müll. Arg.) Aptroot & Lücking develops ascomata with fused ostioles covered with the thallus, produces isohypocrellin and has mostly shorter ascospores (100-130 μm) ( Aptroot and Lücking 2016). Astrothelium variabile Flakus & Aptroot has aggregated ascomata in well-delimited and white pseudostromata, not fused ostioles, lacks pigments and produces lichexanthone ( Flakus et al. 2016). Astrothelium xanthosuperbum Aptroot & M. Cáceres differs in black, raised above the thallus pseudostromata, which are usually in lines, the lack of pigments and the production of lichexanthone ( Aptroot and Cáceres 2016).

Figures

Figure 2. Astrothelium chulumanense (holotype) A, B thallus and ascomata C vertical cross section through pseudostromata D horizontal cross section through pseudostromata E asci (violet ascospores in Lugol's solution) F ascospores (violet in Lugol's solution). Scale bars: 1000 μm (A, B); 500 μm (C, D); 50 μm (E); 10 μm (F).