Enterographa confusa Ertz & Van den Broeck, 2018

Broeck, Dries Van Den & Ertz, Damien, 2018, Enterographa confusa sp. nov. (Roccellaceae, Arthoniales) discovered by chance in type material of its host lichen Arthonia ochraceella, described more than a century ago, Phytotaxa 343 (1), pp. 89-93 : 90

Enterographa confusa Ertz & Van den Broeck spec. nov. ( Fig. 1 )

MycoBank 823817

Diagnosis: A lichenicolous species of Enterographa characterized by punctiform ascomata immersed in the host thallus, (6–)8-spored asci and 3-septate ascospores of 17–23 × (2.5–)3 μm with a distinct gelatinous sheath of 1.5(–2) μm.

Type: — CUBA. C. Wright, #Graphid. Cub. 121c (holotype G!; barcode G00290277) .

Thallus absent (lichenicolous). Ascomata punctiform, immersed in the host thallus, emarginate, discrete or rarely two confluent, 60–115 μm diam.; hymenial disc exposed, pale yellowish to pale brown. Excipulum hyaline, rudimentary, not well separated from the hymenium and the epihymenium. Epihymenium hyaline to pale yellowish, I+ immediately red, KI+ blue. Hymenium hyaline, not inspersed, 60–80 μm; hymenial gel I+ immediately dark red, KI+ blue. Subhymenium hyaline, c. 10–15 μm. Paraphysoids branched, anastomosed, 1–2 μm, not or slightly enlarged at the apex. Asci ellipsoid to clavate, (6–)8-spored, 40–48 × 13–16 μm; wall with a distinct I+ red, KI+ blue ring around a tiny ocular chamber. Ascospores hyaline, fusiform, 3-septate, 17–23 × (2.5–)3 μm (N=20); gelatinous sheath distinct, hyaline, 1.5(–2) μm in water. Conidiomata not seen.

Etymology: —The specific epithet refers to the possible confusion of the ascomata of the lichenicolous fungus with younger ones of the host lichen.

Distribution and ecology: —The species is only known from the type locality of its host, Arthonia ochraceella , in Cuba, on bark.

Remarks: —The new species is lichenicolous on the thallus of Arthonia ochraceella and can be easily overlooked because the ascomata are tiny, pale and of similar colour than those of the host. It was discovered by chance by examining a type specimen of Arthonia ochraceella from herbarium G (G00290277). At first, we did not notice the presence of a lichenicolous fungus on the specimen. By doing a cross section of what we believed to be a young ascoma or pycnidium of Arthonia ochraceella and by its examination under the microscope, it became immediately clear that the fungus was not related to Arthoniaceae because of the combination of ellipsoid to clavate asci with a thin upper wall and the fusiform narrow ascospores having a thick gelatinous sheath. Once detected, the ascomata of the lichenicolous fungus were rather easy to distinguish from those of the host that are much larger when mature, often slightly darker and elongated. The thallus of the host becomes also slightly paler when the lichenicolous fungus is present. Moreover, A. ochraceella is very different microscopically having Arthonia type asci and much larger macrocephalic ascospores (see description below). The new species fits well with the genus Enterographa by emarginate ascomata, ellipsoid to clavate asci with a KI+ blue ring and transversally septate, isolocular, and fusiform ascospores usually having a distinct gelatinous sheath. Among the lichenicolous Enterographa species, E. punctata Ertz & Diederich in Ertz et al. (2005: 128) known from Sri Lanka, is the most similar and differs by gall-inducing ascomata, slightly larger ascomata (up to 170 μm diam.), a taller hymenium that is I+ persistently blue above, 6-spored asci and a different host lichen genus (an unidentified Lobaria species with a green photobiont). Enterographa bagliettoae F. Seavey & J. Seavey in Seavey et al. (2017: 221) is very different by ascomata immersed in raised white galls on the thallus of saxicolous Verrucariaceae . Enterographa osagensis C.A. Morse (2013: 234) on saxicolous Bacidina has shorter and wider spores, 12–15(–17.5) × 3.5–4.5 μm. Enterographa mazosiae R. Sant. ex Matzer & R. Sant. in Matzer (1996: 54) is lichenicolous on Mazosia and differs by distinctly lirelliform, stellately branched ascomata having a dark reddish to blackish hymenial disc ( Matzer 1996; Sparrius 2004). Enterographa brezhonega Sparrius & Aptroot (2007: 315) is very different by shortly lirelliform ascomata immersed in pseudostromata, 4-spored asci, and (4–)6-septate ascospores. Enterographa epiphylla (Sérus.) Ertz, Diederich & Sparrius in Ertz et al. (2005: 126), E. fellhaneroides Yeshitela, Eb. Fisch., Killmann & Sérus. in Yeshitela et al. (2009: 18) and E. meklitiae Yeshitela, Eb. Fisch., Killmann & Sérus. in Yeshitela et al. (2009: 20) are all lichenicolous on foliicolous Coenogonium species and differ by 4 or 4–6-spored asci and more than 3-septate ascospores. Enterographa epigraphis Etayo & Sipman in Etayo (2017: 190) is very unusual for a lichenicolous Enterographa species because of the large ascospores with an ontogeny reminding the genus Fulvophyton (Ertz & Tehler 2011) .

Specimen G00290277 is both, the lectotype of Arthonia ochraceella and the holotype of Enterographa confusa . Amazingly, A. ochraceella was described in 1890, but 128 years were necessary before the lichenicolous fungus present on the same type material was detected and described.

Figures

FIGURE 1. Enterographa confusa (A–E, holotype, G). A. E. confusa (black arrows point to ascomata of the lichenicolous fungi) forming a paler, whitish area in the thallus of its host, Arthonia ochraceella (white arrows point to ascomata of the host lichen). B. Ascomata of E. confusa. C. Asci in water. D. asci in KI showing the KI+ blue apical ring. E. Ascospores in water. Scale in A = 500 μm, in B = 100 μm, in C–D = 10 μm, in E = 5 μm. (Photos D. Ertz).