Two new species of Astrothelium (Trypetheliaceae) with amyloid ascospores inhabiting the canopy of Quercus humboldtii trees in Colombia Simijaca, Diego Lücking, Robert Moncada, Bibiana Phytotaxa 2021 2021-06-21 508 2 229 234 B2SDY Simijaca, Lucking & Moncada Simijaca, Lucking & Moncada 2021 [136,817,1108,1135] Dothideomycetes Trypetheliaceae Astrothelium Fungi Trypetheliales 1 230 Ascomycota species mordonialense sp. nov.  Differing from  Astrothelium amylosporumin 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 typelocality, 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 NaturalROGITAMA, 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 mmdiam, 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. amylosporumFlakus & 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 bullatumFlakus & Aptrootforms lateral ostioles and the ascomata are fully immersed between bullate thallus portions ( Flakus et al.2016).  Astrothelium palaeoexostemmatisSipman & Aptrootis 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. flavoduplexAptroot & M. Cáceresand  A. ochroleucoidesAptroot & M. Cáceresdeviate by producing lichexanthone ( UV+ yellow);  A. flavoduplexdiffers 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. mordonialensisin 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. tetrasporumAptroot & M. Cáceresand  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).   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.  Additional specimen examined:  COLOMBIA. Dept. Boyacá: Arcabuco, Vereda Peñas Blancas, Sector Mordoñal, Reserva NaturalROGITAMA, 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). IF558501 [260,369,1144,1171] 1 230 1 2015-07-12 UDBC Colombia Arcabuco 2530 5.796472 Sector Mordonal 1 -73.44889 Vereda Penas Blancas 1 230 2 Boyaca holotype 2015-07-12 UDBC Colombia Arcabuco 2530 5.796472 Sector Mordonal 1 -73.44889 Vereda Penas Blancas 2 231 1 Boyaca