Porina madagascariensis Debaene & Ertz 2026, sp. nov.

Porina madagascariensis Debaene & Ertz sp. nov. Fig. 10 Type. MADAGASCAR • Diego Suarez Province, Antsiranana, West of Sambava, Marojejy National Park, along trail from Camp Simpona down to Camp Marojejia, rather dense humid montane forest, 14°26'20"S, 49°45'08"E, alt. ca. 1200 m, 23 Oct. 2014; Ertz 20279 O (holotype: BR 5030171998917; isotype: TAN). Etymology. The epithet refers to the occurrence of the only known specimen in Madagascar. Diagnosis. This species differs from Porina bellendenica Müll. Arg. in its foliicolous habit (vs. corticolous and saxicolous in P. bellendenica); the absence of a dark-brown prothallus; broader perithecia (0.7–0.9 mm in diam. in P. madagascariensis vs. 0.35–0.6 mm in diam. in P. bellendenica); and a paler periostiolar area (red to brown in P. madagascariensis vs. dark-brown to black in P. bellendenica). Description. Thallus epiphyllous; continuous and marginally dispersed, large, ca. 20–30 mm wide, and ca. 30 µm thick; surface smooth to slightly uneven, encrusted with calcium oxalate crystals; slightly glossy; pale yellowish green. Photobiont angular-rounded, irregularly arranged; ca. (4 –) 6–13 (– 15) × 2–4 (– 5) µm (n = 33). Perithecia superficial, not well delimited from thallus due to strongly spreading base, immature perithecia lens-shaped, mature perithecia lens-shaped to subhemispherical; smooth to slightly irregular surface, glabrous; ca. 0.7–0.9 mm diam. (n = 13), and ca. 200–250 µm high; covered by ca. 10–20 µm thick algiferous thallus layer; concolorous to slightly more yellowish than thallus; periostiolar area red to brown, getting darker and broader with age (ca. 0.2–0.3 mm), apex applanate with ostiole region sometimes slightly depressed. Crystallostratum ca. 10–20 µm thick. Excipulum ca. 15–20 µm thick; hyaline to yellow, K + pale yellow to orange. Involucrellum ca. 30–45 µm thick; yellow, K + orange to red. Hamathecium hyaline; not inspersed; composed of thin, simple paraphyses ca. 1–1.5 μm diam., and ca. 70–120 µm long. Asci fusiform; 110–135 × 13–15 µm (n = 6); 8 - spored; with apical ring structure. Ascospores (9 –) 10–12 (– 14) - septate, bacillar to narrowly oblong (45.5 –) 48–55 (– 64) × (3.5 –) 3.9–4.4 (– 4.7) µm, ratio L / B (10.4 –) 11.2–13.8 (– 18.3) (n = 80); 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 only one locality in northern Madagascar. It inhabits leaf surfaces in rather dense, humid montane forests at moderate elevation (ca. 1200 m). Notes. In the ITS and mtSSU phylogenies, P. madagascariensis forms an isolated lineage within the Phylloporina clade and is not closely related to any other sampled accession (Figs 2, 3). Distinct brown dots are visible on the specimen’s thallus (Fig. 10 A), but they occur across the entire leaf surface and are therefore not associated with the species itself. Porina madagascariensis most closely resembles P. bellendenica in its ascospore morphology, with (9 –) 10–12 (– 14) - septate ascospores measuring (45.5 –) 48–55 (– 64) × (3.5 –) 3.9–4.4 (– 4.7) µm, closely matching the (9 –) 11–13 (– 15) - septate ascospores (32–56 × 3–5 µm) reported for P. bellendenica by McCarthy (2013). It differs, however, in being foliicolous rather than corticolous or saxicolous; in having broader, lens-shaped to subhemispherical perithecia with a red to brown periostiolar area instead of hemispherical perithecia with a dark-brown to black periostiolar area; in the absence of a dark-brown prothallus; and in the apparent absence of pycnidia. Moreover, the currently available mtSSU accessions for P. bellendenica are recovered in the Phyllophiale clade (See Suppl. material 3), whereas P. madagascariensis belongs to the Phylloporina clade. Porina madagascariensis is additionally one of the few foliicolous members of the Phylloporina clade that deviate from the predominantly 7 - septate ascospore type. Similar increases in ascospore septation have previously been reported in several Porinaceae species (Lücking 2008: 337), e. g. Porina virescens (Kremp.) Müll. Arg., which includes a multi-septate form with 7–11 (– 15) - septate ascospores (Lücking and Vězda 1998; Lücking 2004). The species was recovered in association with algal haplotype 26: 2 (Fig. 10 D, E), which is shared with several other Phylloporina - clade taxa, such as P. complanata (Figs 4, 5). The combination of a distinct phylogenetic position and diagnostic differences supports the recognition of P. madagascariensis as a distinct species.