Arthothelium frischianum Van den Broeck & Ertz, 2017

Broeck, Dries Van Den, Tehler, Anders, Razafindrahaja, Tahina & Ertz, Damien, 2017, Four new species of Arthothelium (Arthoniales, Ascomycetes) from Africa and Socotra, Phytotaxa 331 (1), pp. 51-64 : 55-56

Arthothelium frischianum Van den Broeck & Ertz sp. nov. ( Fig.2A − F )

MycoBank 822913

The new species differs from all other corticolous Arthothelium species having ascospores with a larger terminal cell by minute (0.2– 0.6 × 0.2–0.4 mm) brownish-black ascomata in combination with ascospores of 45–55.5 × 19–24.5 μm and an inconspicuous hypothecium.

Type: — MADAGASCAR. Province Diego Suarez: Antsiranana, region Diana, district Diego II, commune Joffreville, Forontany, Morafeu, Parc National de la Montagne d’Ambre, along trail from Gîte des Roussettes to lookout over Cascade Antakarana, through moist, mostly secondary montane forest, from 12°31’37.5”S, 49°10’18.8”E, 1068 m to 12°29’57.3”S 49°10’29.8”E, 880 m, 9 October 2014, D. Ertz 19511 (holotype: BR!, isotype: TAN).

Thallus corticolous, crustose, white to greenish, smooth to slightly rough, following the cracks of the bark, slightly shiny, ca. 50–100 μm thick. Prothallus brown. Photobiont not observed, doubtfully lichenized. Ascomata 0.2–0.6 × 0.2–0.4 mm, minute, sparsely distributed, ± first immersed in the thallus, bursting through it to become sessile, rounded to elongate, not stellate, often covered laterally by a thin layer of thallus, scattered more or less evenly over the thallus; disc brownish-black, not pruinose but often with some remnants of thallus, wet more brownish and partly transparent, rough, without visible margin. Excipulum inconspicuous. Epihymenium 10–30 μm thick, indistinct, hyphae hyaline to brown, intermingled with an amorphous brown pigment, slightly darkening in K. Hymenium 150–180 μm tall, hyaline to brownish, I+ red, K/I+ deep blue. Paraphysoids hyaline, tips without dark caps and walls, sometimes slightly swollen, densely branched and netted, ca. 1.7–2.3 μm wide. Hypothecium inconspicuous. Asci 85–100 × 70–80 μm (N = 2), globose, 8-spored, with K/I+ blue ring like structure in the tholus. Ascospores 45–55.5 × 19–24.5 μm (N = 13), muriform, persistently hyaline, ovoid, with one larger terminal cell, rest of the cells divided by 6–8 transversal and 1–4 longitudinal septa; gelatinous sheet not observed; spore ontogeny not observed. Pycnidia not observed.Thallus K–, C–, KC–, PD–, UV–. Calcium oxalate not observed. TLC (solvent B): no secondary metabolites observed.

Distribution and ecology: — Arthothelium frischianum is at present only known from the type location in northern Madagascar.

Etymology: —This new species is dedicated to Andreas Frisch for his outstanding work on Arthoniaceae .

Remarks: —The new species is similar to Arthothelium loandense ( Vainio 1901: 447) Zahlbruckner (1922: 128 in Zahlbruckner 1924) that differs by smaller ascospores (35 × 14 μm according to the protologue and 20.5–28.5 × 10–12 μm according to our own observations of the type) (BM!) becoming brown and a K+ olivaceous green reaction of the brown epihymenium. A. bessale ( Nylander 1873:174) Zahlbruckner (1922: 122 in Zahlbruckner 1924) is also very close but differs by smaller ascospores (10–20 μm broad according to our own observations of the type (M!), 15–16 μm according to the protologue) and much larger ascomata (1–2.2 mm according to our observations, 0.5–0.9 mm fide Nylander 1873). Of the other 18 species with a larger terminal cell: A. adveniens ( Nylander 1868: 102) Müller Argoviensis (1887a: 76) , A. ampliatum (C. Knight & Mitten 1860: 106 in Knight & Mitten 1862) Müller Argoviensis (1893b: 61), A. chiodectoides ( Nylander 1869b: 72) Zahlbruckner (1922: 122 in Zahlbruckner 1924), A.dictyosporum (Coppins & P. James 1979: 11) Coppins (1989: 210) , A. fuscoroseum Makhija & Patwardhan (1995b: 211) , A. impolitellum ( Nylander 1867b: 7) Makhija & Patwardhan (1995b: 211) , A. infuscatum ( Krempelhuber 1876: 459 in von Krempelhuber 1876) Müller Argoviensis (1894b: 84), A. macounii (G. Merrill 1914: 36) W.J. Noble (1987: 91 in Ahti et al. 1987), A. obtusulum ( Nylander 1888a: 123) Müller Argoviensis (1894b: 84) , A. pellucidum (C. Knight 1883: 352 in Knight 1883) Müller Argoviensis (1894b: 84), A. ramosum Makhija & Patwardhan (1995b: 216) , A. subbessale ( Nylander 1891: 23) Makhija & Patwardhan (1995a: 210) and A. violaceoatrum Makhija & Patwardhan (1995b:220) all have smaller ascospores (12–46 × 3–20 μm) ( Nylander 1868, 1869b; von Krempelhuber 1876; Nylander 1888a; Müller 1893b, 1894b; Coppins & James 1979; Ahti et al. 1987; Makhija & Patwardhan 1995a, 1995b; Smith et al. 2009) while the ascospores of A. pseudolirellinum Makhija & Patwardhan (1995b: 215) are distinctly larger (53–70 × 20–22 μm). The ascospores of A. picilum A. Massalongo in von Krempelhuber (1871: 867) are ± as broad (20–22 μm) as those of the new species but are distinctly shorter (33–36 μm) ( von Krempelhuber 1871). A. aphanocarpum ( Nylander 1856: 90) Zahlbruckner (1922: 121 in Zahlbruckner 1924) and A. corticatum Makhija & Patwardhan (1995b: 208) are characterized by I+ blue ascomatal gel and more or less lirellate larger ascomata ( Nylander 1856; Makhija & Patwardhan 1995b). A. thoraciferum ( Vainio 1921: 297) Zahlbruckner (1922: 137 in Zahlbruckner 1924) differs from the new species by narrower ascospores (10–20 μm broad against 19–24.5 μm in the new species) becoming distinctly dark brown at maturity and larger ascomata (1–1.5 mm) ( Makhija & Patwardhan 1995b).

Figures

FIGURE 2. New species of Arthothelium from Africa and Socotra. Arthothelium frischianum (A−F, holotype), Arthothelium miesii (G−N, holotype). A−B, G−H. Thallus with apothecia. C, I. Ascus in water. D−F, J−N. Ascospores. Scale in A, G = 1000 μm, in B, H = 500 μm, in C = 25 μm, in D−F, I = 10 μm, in J−N = 5 μm.