Porina parva Debaene, Diederich & Ertz 2026, sp. nov.

Porina parva Debaene, Diederich & Ertz sp. nov. Fig. 12 Type. MADAGASCAR • Toliara Province, ca. 25 km Northwest of Fort-Dauphin (Tolagnaro), National Park of Andohahela, South part of parcel 1, 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 25301 E (holotype: BR 5030171996852; isotype: TAN). Etymology. The epithet refers to the small thallus and perithecia of the species. Diagnosis. This species differs from Porina epiphylloides Vězda in its small thallus, often scattered in patches; in usually larger perithecia (0.2–0.4 mm in diam. in P. parva vs. 0.24–0.25 mm in P. epiphylloides); the presence of pycnidia; in larger asci (65–100 × 17–31 µm vs. 65–70 × 8–10 µm); and in ascospores, which are slightly longer and wider (26.5–42 × 3–6.2 µm in P. parva vs. 26–34 × 3–3.5 µm in P. epiphylloides). Description. Thallus epiphyllous; mostly in small, irregular patches and sometimes confluent, ca. 0.5–5 mm wide, and ca. 15–25 µm thick; rarely with a whitish translucent prothallus; rugose to distinctly verrucose, verrucae ca. 0.05 mm diam., encrusted with calcium oxalate crystals; matt to slightly glossy; greyish green to yellowish green or green with orange tinge. Photobiont rectangular, forming radiate plates; ca. (8 –) 10–14 (– 18) × (3 –) 4–6 (– 7) µm (n = 168). Perithecia superficial, not well delimited from the thallus; immature perithecia lens-shaped, mature perithecia lens-shaped to hemispherical (rarely almost wart-shaped); surface smooth to slightly rough, glabrous; ca. 0.2–0.4 mm diam. (n = 48), and ca. 140–160 µm high; covered by a ca. 5–10 µm algiferous thallus layer; concolorous to slightly more yellowish than the thallus or pale orange to brown; apex slightly applanate to convex; ostiole inconspicuous. Crystallostratum ca. 25–50 µm thick. Excipulum ca. 15–20 µm thick; hyaline, K + pale yellow. Involucrellum ca. 20–35 µm thick; hyaline to greyish brown, K + yellow to orange. Hamathecium hyaline; not inspersed; composed of thin, simple paraphyses ca. 1–2.5 μm diam., and ca. 70–100 µm long. Asci fusiform to obclavate; (65 –) 76–90 (– 100) × (17 –) 20–26 (– 31) µm (n = 31); 8 - spored; with apical ring structure. Ascospores 7 - septate, oblong to narrowly fusiform (26.5 –) 32–38 (– 42) × (3 –) 4.1–5.3 (– 6.2) µm, ratio L / B (5.2 –) 6.3–8.8 (– 12.7) (n = 257), gelatinous sheath not or poorly visible. Pycnidia ca. 0.1 mm diam.; lens-shaped; smooth, glabrous; concolorous to yellowish. Conidiophores reduced to the conidiogenous cell; conidiogenesis enteroblastic, phialidic; conidiogenous cells elongate ampulliform, 5–6 × 3–3.5 µm. Microconidia ellipsoid to fusiform; (2.5 –) 2.6–3.3 (– 3.6) × (0.8 –) 0.9–1.2 (– 1.3) µm (n = 21). Chemistry not tested for thallus; TLC not performed. Distribution and ecology. The species is known from three localities in Mauritius and three in southern Madagascar. It inhabits leaf surfaces in dense, humid, evergreen forests, often near rivers, at low to moderate elevations (ca. 345–1000 m). Notes. Porina parva was recovered as a distinct lineage within the Porina s. str. clade in both the mtSSU and ITS phylogenies, although it exhibited a relatively high intraspecific genetic divergence compared with other members of the clade (Figs 2, 3). The species is represented by six specimens from Mauritius and four from southern Madagascar, all of which are morphologically similar. Porina epiphylloides is considered the most similar species based on both morphology and phylogenetic affinity. However, P. parva differs in possessing generally larger perithecia, considerably larger asci, slightly longer and broader ascospores, and pycnidia, which have not been reported for P. epiphylloides. Most specimens formed small, discrete thalli bearing only a few perithecia, although two confluent specimens produced pycnidia, 25301 E (Fig. 12 A) and 25309 C. Better-preserved material often exhibited an orange tinge on the thallus, caused by photobiont pigmentation (Fig. 12 B). Porina parva showed high photobiont flexibility and was associated with five algal haplotypes distributed across two major rbc L clades (29: 2, 29: 3, 29: 4, 29: 5, and 33: 1) (Figs 4, 5). The combination of a distinct phylogenetic position, consistent morphology across specimens, and diagnostic differences supports the recognition of P. parva as a distinct species. Additional specimens examined. MADAGASCAR – Toliara Prov. • ca. 25 km Northwest of Fort-Dauphin (Tolagnaro), National Park of Andohahela, South part of parcel 1, 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 25301 D (BR, TAN) • ibid., 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 and humid forest, 28 Nov. 2019; Ertz 25309 C (BR, TAN). • ibid., 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 25411 B (BR, TAN). – MAURITIUS – Rivière Noire District • Black River Gorges National Park, 5 km North-West of Pétrin, Brise Fer Forest, 20°22'40"S (ca. 200 m), 57°26'25"E (ca. 200 m), 585 m, 10 Sep. 2019; Ertz 24305 I (BR, MAU), 24305 G (BR) and Diederich. • ibid., along trail from Plaine Champagne towards Piton de la Petite Rivière Noire, 20°24'52"S (ca. 1000 m), 57°24'43"E (ca. 500 m), alt. 630–800 m, dense evergreen mountainous forest, 07 Sep. 2019; Ertz 23965 A (BR), 23968 B (BR, MAU), 23981 D (BR). • ibid., Chamarel, Ebony Forest, South-West part of forest, 20°26'13"S (ca. 50 m), 57°22'06"E (ca. 50 m), alt. 345 m, 02 September 2019; Ertz 23650 H and Diederich (BR).