Astrothelium mordonialense Simijaca, Lücking & Moncada, 2021

Simijaca, Diego, Lücking, Robert & Moncada, Bibiana, 2021, Two new species of Astrothelium (Trypetheliaceae) with amyloid ascospores inhabiting the canopy of Quercus humboldtii trees in Colombia, Phytotaxa 508 (2), pp. 229-234 : 230-231

Astrothelium mordonialense Simijaca, Lücking & Moncada , sp. nov. ( Fig. 1 )

Mycobank IF558501

Differing from Astrothelium amylosporum in having 4 ascospores per ascus, in the smaller ascospores, and in the ascomata being mostly covered by a thallus layer.

Etymology: The epithet refers to the type locality, the Sector Mordoñal of the Vereda Peñas Blancas in which the ROGITAMA reserve is located.

Holotype:— COLOMBIA. Dept. Boyacá: Arcabuco, Vereda Peñas Blancas, Sector Mordoñal , Reserva Natural ROGITAMA, 05º47’47.3” N, 73º26’56.0”W, elev. 2530 m, in oak forest, on bark of Quercus humboldtii , 12 July 2015, Simijaca et al. 2662 ( UDBC, holotype!)

Thallus corticolous, distinctly corticate, olive-green to pale green, smooth to uneven. Ascomata solitary to somewhat aggregate but not pseudostromatic, with apical, separate ostioles, 1–1.3 mm diam, erumpent, covered by thallus except for the broad, dark ostiolar area surrounded by a thin, irregular whitish rim, darkening when dry. Hamathecium inspersed. Ascospores 4 per ascus, muriform, with 9–11 transverse and 3–4 longitudinal septa per segment, with the distinct diamond-shaped lumina and with a pronounced median septum, ellipsoid to fusiform, 100– 110 × 24–30 µm, IKI+ blue.

Chemistry: Secondary substances absent; thallus surface UV-, K-, medulla K-; ascomata surface UV-.

Amyloid ascospores are comparatively rare in the genus Astrothelium ( Aptroot & Lücking 2016) . Among species with muriform ascospores and lacking secondary compounds, the most similar is A. amylosporum Flakus & Aptroot , which differs by its larger ascospores (125–170 ×27–40 µm) occurring in numbers of 8 per ascus and in the fully exposed, brown-black ascomata (( Flakus et al. 2016). Astrothelium bullatum Flakus & Aptroot forms lateral ostioles and the ascomata are fully immersed between bullate thallus portions ( Flakus et al. 2016). Astrothelium palaeoexostemmatis Sipman & Aptroot is overall similar to the new species, including ascospore size, but the ascospores are richly muriform, with numerous small cells and thin septa and walls, not displaying diamond-shaped lumina ( Aptroot et al. 2019). Both A. flavoduplex Aptroot & M. Cáceres and A. ochroleucoides Aptroot & M. Cáceres deviate by producing lichexanthone ( UV + yellow); A. flavoduplex differs further in the strongly pseudostromatic ascomata covered with yellow-orange pigment and the longer ascospores (110–350 × 20–27 µm), whereas in A. ochroleucoides , which agrees with A. mordonialensis in ascospore number and size (80–115 × 15–24 µm), the pseudostromatic ascomata are exposed and brown-black ( Aptroot & Cáceres 2016). Two similar species, but with non-amyloid ascospores, are A. tetrasporum Aptroot & M. Cáceres and A. alboverrucum (Makhija & Patw.) Aptroot & Lücking : the first has larger ascospores (145–175 × 30–35 µm), bullate thallus, and ascomata covered by thallus except the protruding ostiole, whereas the former specie also has larger ascospores (85–170 × 23–33 µm) and its ascomata are hemispherical with a whitish cover ( Aptroot & Lücking 2016).

Additional specimen examined: COLOMBIA. Dept. Boyacá: Arcabuco, Vereda Peñas Blancas, Sector Mordoñal , Reserva Natural ROGITAMA, 05º47’47.3”N, 73º26’56.0”W, 2530 m, in oak forest, on bark of Quercus humboldtii , 12 July 2015, Simijaca et al. 2705, 2718 ( UDBC) .

Figures

FIGURE 1. Astrothelium mordonialense.A. Thallus with perithecia; B. Perithecia enlarged showing darkened ostiolar area. C. Hymenium showing asci and ascospores reacting IKI + blue; D. Ascopore. Scale = 1 mm in A–B, 100 µm in C, 10 µm in D.