Porina cincta Debaene & Ertz 2026, sp. nov.

Porina cincta Debaene & Ertz sp. nov. Fig. 8 Type. MADAGASCAR • Toliara Province, ca. 26 km Northwest of Fort-Dauphin (Tolagnaro), National Park of Andohahela, South part of parcel 1, ca. 6.5 km West of the village of Malio, 24°56'24.1"S, 46°43'26.2"E, alt. 1000 m, dense humid forest, 01 Dec. 2019; Ertz 25409 F (holotype: BR 5030171982725; isotype: TAN). Etymology. The epithet refers to the perithecia, which are encircled by a ring of white hairs. Diagnosis. This species differs from Porina dwesica Brusse & C. H. Dickinson in its photobiont, which is irregularly arranged and angular-rounded rather than rectangular in radiate plates; in its involucrellum and excipulum, which show a K + orange – red reaction rather than a K - reaction; and in its ascospores, which are slightly wider than those reported (5.2–6.5 µm in P. cincta vs. 4–5.2 µm in P. dwesica). Description. Thallus epiphyllous; diffuse and dispersed, ca. 10–15 µm thick; smooth, matt; greyish green to pale brownish green, difficult to distinguish from the leaf surface. Photobiont angular-rounded, irregularly arranged; ca. (5 –) 6–9 (– 10) × 3–5 (– 6) µm (n = 9). Perithecia basally immersed in thallus, not well delimited from thallus; immature perithecia lens-shaped to conical, mature perithecia lens-shaped to hemispherical, rarely subglobose when less deeply immersed; smooth surface; ca. 0.3–0.5 mm diam. (n = 10), and ca. 140–200 µm high; pale to dark reddish brown; ring of white hairs surrounding the perithecium at its point of emergence from the thallus, hairs thick and soft, consisting of agglutinated hyphae, ca. 20–100 µm in length and ca. 10–20 µm in width; ostiole inconspicuous, apex slightly applanate. Crystallostratum not present. Excipulum ca. 15–35 µm thick; pale orange to red, K + red. Involucrellum ca. 20–35 µm thick; pale orange to red, K + red. Hamathecium hyaline; not inspersed; composed of thin, simple paraphyses ca. 1–2 μm diam., and ca. 75–100 µm long. Asci obclavate; 85–100 × 18–20 µm (n = 5); 8 - spored; with apical ring structure. Ascospores 7 - septate, broadly oblong to fusiform (30 –) 31.5–34.5 (– 36) × (5.2 –) 5.6–6.1 (– 6.5) µm, ratio L / B (5.2 –) 5.3–6 (– 6.4) (n = 52). Pycnidia not observed. Chemistry not tested for thallus; TLC not performed. Distribution and ecology. The species is known from only one locality in southern Madagascar. It inhabits the upper surface of leaves in rather dense, humid montane forests at moderate elevation (ca. 1000 m). Notes. Because the thallus of the single specimen was difficult to distinguish from the leaf surface (Fig. 8 A), its width could not be estimated. Multiple solitary perithecia were found across the host leaf, suggesting diffuse colonisation without the formation of large confluent thalli. The host leaf was rather stiff and thick (possibly Pandanus sp.), unlike many of the other leaves bearing foliicolous lichens. Porina cincta was compared with the unsequenced P. dwesica, the morphologically most similar species, originally reported from South Africa (Transkei district, now Eastern Cape province) by Brusse and Dickinson (1991). Both species share similarly coloured perithecia and a ring of white hairs, although the fawn-coloured perithecia described for P. dwesica appear paler than those of P. cincta. Furthermore, photographs accompanying the original description show numerous soft white hairs extending from the base to the apex of the perithecia, whereas in P. cincta, the hairs are fewer and confined to the basal region (Fig. 8 B). The most distinctive difference between the two species lies in the anatomy and chemistry of the perithecial inner walls. Porina cincta possesses a 20–35 µm thick, pale orange to red involucrellum (Fig. 8 C) with a distinctly K + orange to red reaction (Fig. 8 E), whereas P. dwesica has a ca. 10 µm thick hyaline involucrellum that is K -. In addition, P. dwesica bears pycnidia and occasionally produces 9 - septate ascospores, neither of which was observed in P. cincta. The two species also differ in photobiont morphology, with P. dwesica possessing rectangular cells arranged in radiate plates, whereas P. cincta has irregularly arranged angular-rounded photobiont cells (Fig. 8 D). Although no rbc L sequence was recovered for this species, the photobiont morphology resembles that of P. cf. leptosperma (Fig. 7 A, B), which is associated with the 33: 3 algal haplotype, particularly in its relatively large intercellular spaces. In both the mtSSU and ITS phylogenies, P. cincta was recovered within the Trichothelium clade, despite possessing K + orange to red perithecial walls that contrast with the predominantly black K - perithecia characterising most members of that lineage. The combination of a distinct phylogenetic position and diagnostic differences supports the recognition of P. cincta as a distinct species.