Porina complanata Debaene & Ertz 2026, sp. nov.

Porina complanata Debaene & Ertz sp. nov. Fig. 9 Type. MADAGASCAR • Toliara Province, ca. 26 km Northwest of Fort-Dauphin (Tolagnaro), National Park of Andohahela, South part of parcel 1, ca. 6 km West of the village of Malio, 24°55'46.9"S, 46°43'55.9"E, alt. 515 m, dense humid forest, 28 Nov. 2019; Ertz 25321 B (holotype: BR 5030171983753; isotype: TAN). Etymology. The epithet refers to the flattened or immersed perithecia. Diagnosis. This species differs from Porina australiensis (Lücking & Vězda) Lücking in usually having completely applanate perithecia (vs. lens-shaped perithecia with applanate tops in P. australiensis); in having an unevenly rugose thallus (vs. smooth in P. australiensis); and in having narrower ascospores (3.4–4.7 µm in P. complanata vs. 5–6 µm in P. australiensis). Description. Thallus epiphyllous; diffuse to continuous and marginally dispersed, ca. 3–15 mm wide, and ca. 30 µm thick; often a whitish translucent prothallus present between patches at the margins; unevenly rugose, incrusted with calcium oxalate crystals; matt to slightly glossy; pale greyish green to yellowish green. Photobiont angular-rounded, irregularly arranged; ca. (5 –) 6–13 (– 18) × (2 –) 3–5 (– 6) µm (n = 34). Perithecia immersed to superficial, not well delimited from thallus, usually completely applanate, occasionally becoming weakly lens-shaped; uneven surface, glabrous; ca. 0.5–0.9 mm diam. (n = 33), and ca. 50–100 µm high; covered by ca. 10 µm thick algiferous thallus layer; greenish-yellow to pale yellow, periostiolar area reddish to brown (ca. 0.05–0.2 mm), ostiolar depression sometimes present in mature perithecia with darker reddish-brown circle appearing around ostiole of ca. 0.1–0.2 mm diam. Crystallostratum ca. 15–30 µm thick. Excipulum ca. 15–20 µm thick; hyaline, K + pale orange. Involucrellum ca. 30–50 µm thick; greyish brown, K + orange to red. Hamathecium hyaline; not inspersed; composed of thin, simple paraphyses ca. 1–2 μm diam., and ca. 60–80 µm long. Asci narrowly fusiform; 90–120 × 9–13 µm (n = 9); 8 - spored; with apical ring structure. Ascospores 7 - septate, oblong to narrowly fusiform, (27.5 –) 30–35 (– 40.5) × (3.4 –) 3.7–4.3 (– 4.7) µm, ratio L / B (6.5 –) 7.3–8.9 (– 10.5) (n = 132), gelatinous sheath not or poorly visible. Pycnidia not observed. Chemistry not tested for thallus; TLC not performed. Distribution and ecology. The species is known from four different localities in Madagascar. It inhabits the surfaces of leaves in rather dense, humid forests and open mixed woodlands at low to moderate elevations (ca. 360–1177 m). Notes. Porina complanata most closely resembles P. australiensis in its similar photobiont morphotype and overlapping 7 - septate ascospore length. It differs, however, in having completely applanate to immersed perithecia rather than lens-shaped perithecia with an applanate apex, an unevenly rugose thallus, narrower ascospores, and an apparent absence of pycnidia, which are frequently present in P. australiensis (Lücking and Vězda 1998). The species also resembles P. subapplanata Malcolm, Vězda, P. M. McCarthy & Kantvilas, as well as P. pseudoapplanata Lücking & M. Cáceres, in possessing applanate or immersed perithecia (Fig. 9 A, B). Both species differ in having rectangular photobionts arranged in radiate plates, whereas P. complanata has angular-rounded photobionts arranged irregularly (Fig. 9 E). Porina subapplanata is further distinguished by its occasionally white – pubescent ostiole, broader asci and ascospores, and the apparent absence of an ostiolar depression surrounded by a dark reddish-brown circle, according to the original description by Malcolm et al. (1999). Porina pseudoapplanata differs in having a smooth thallus, isidia, no crystals in the thallus or perithecia, a more prominent perithecial apex, shorter asci, slightly narrower ascospores, and perithecia that are never immersed, according to the original description by Lücking and Cáceres (1999). No confirmed sequences of P. australiensis, P. subapplanata, and P. pseudoapplanata are currently available for comparison. The single specimen identified as P. australiensis in this study does not cluster with the P. complanata sequences in either phylogeny (Figs 2, 3). Porina complanata lineage is represented by six sequenced specimens forming two subgroups within the Phylloporina clade. The relationship between these subgroups receives significant support values (BS = 79) in the ITS phylogeny but is unsupported in the mtSSU phylogeny (BS = 55). Both subgroups are nearly morphologically identical. Although the subgroup comprising specimens 20270 I, 20270 B, and 25303 C tends to have more immersed perithecia, the other subgroup tends to have more flattened perithecia that protrude slightly from the thallus surface. Furthermore, this species was recovered in association with four different algal haplotypes (26: 1, 26: 2, 26: 7, and 26: 11), indicating substantial symbiotic flexibility. Additional data are needed to determine whether the observed genetic divergence supports recognition of more than one species. Additional specimens examined. MADAGASCAR – Toliara Prov. • ca. 26 km Northwest of Fort-Dauphin (Tolagnaro), National Park of Andohahela, South part of parcel 1, ca. 6 km West of the village of Malio, 24°55'46.9"S, 46°43'55.9"E, alt. 515 m, dense humid forest, 28 Nov. 2019; Ertz 25322 D (BR, TAN). • ibid., ca. 5 km West of the village of Malio, 24°55'43.4"S, 46°44'37.2"E, alt. 360 m, dense and humid forest at the bottom of a valley near a river bordered by large granite boulders, 27 Nov. 2019; Ertz 25303 C (BR, TAN). – Diego Suarez Prov. • Antsiranana, West of Sambava, Marojejy National Park, along trail from Camp Mantella to Camp Marojejia, rather dense humid evergreen lower montane forest, 14°26'07"S, 49°46'05"E, alt. ca. 650 m, 18 Oct. 2014; Ertz 20227 D (BR, TAN). • ibid., Region: Diana, District: Diego II, Commune: Joffreville, Forontany: Morafeu, National Park of Montagne d’Ambre, Gîte des Roussettes, mixed open woodland, around house and picnic area, 12°31'37"S, 49°10'18"E, alt. 1068 m, 6 Oct. 2014, Ertz 20270 I, 20270 B (BR, TAN).