Asplenium ramicola Eb. Fisch. & Lobin 2023, sp. nov.

Holotype: — RWANDA. Western Province: Nyungwe NP, Gisakura, canopy epiphyte (on Pentadesma reyndersii Spirlet (1959: 356), elev. 1953 m, 3 April 2021, S2°26`29.21`` E29°07`02.60``, E.Fischer s.n. (BR0000015253552 V!; isotype: KOBL!).

Diagnosis: —Morphologically similar to A. friesiorum and A. biafranum Alston & F.Ballard (Ballard 1938: t 3367).

From Asplenium friesiorum the new species can be distinguished by the number of lateral pinnae which is 7– 10(12) (vs. 19–24 in A. friesiorum), the terminal section lanceolate to ovate, irregularly pinnatifid, with bases confluent with lateral pinnae (vs. terminal section linear-lanceolate, elongate, lobed to slightly pinnatifid, not confluent with lateral pinnae in A. friesiorum), and in size of scale cells being considerably smaller (Fig. 18 A–D), 0.07–0.08 µm versus 0.12–0.14 µm in A. friesiorum (Fig. 18 E–G). Lastly, the spores are different in size (42–43 ×32.7–37.5 µm in A. ramicola vs. 36.4–39.2 × 25.6–28.5 µm in A. friesiorum) and shape, the ecto-perispore densely reticulate with echinulae usu. not bifid at apex and 6–9.9 µm long in A. ramicola (Fig. 19) vs. reticulate with large openings and echinulae often bifid at apex and 3–5.6 µm long in A. friesiorum (Fig, 20).

From Asplenium biafranum the new species can be distinguished by the smaller scales, 0.55–0.62 mm vs. 1–2 mm in A. biafranum. The number of cells in a transversal row at lower third of the scale does not exceed 17–20 in A. ramicola, while it is generally 29–33 in A. biafranum and 37–41 in A. friesiorum. The spores from the new species have an ecto-perispore densely reticulate with echinulae usu. not bifid at apex and 6–9.9 µm long, while A. biafranum has a reticulate perispore with reduced ecto-perispore giving it a`pseudo-echinulate´ appearance (fide Viane 2021).

Description: —Epiphytic fern. Rhizomes creeping, up to 11.5 cm long, densely scaly; scales dark brown, lanceolate with long filiform apex, 1.8–2.51 × 0.55–0.62 mm at base, × 0.37 mm at middle part, and × 0.17–0.2 mm at apex, cells with prominent dark walls, 0.07–0.08 × 0.03–0.04 µm. Fronds spaced, pendent. Stipes 17.5–22 cm, maroon to dark brown, canaliculated, glabrous. Lamina 22–41.5 × (13.5) 16–22.8 cm, elliptic, 1-pinnate, upper surface green, lower surface greyish-green. Pinnae 9–13 pairs, subopposite, basic pinnae as big as or slightly smaller than the others, tapering; terminal pinna lanceolate to ovate with base confluent with highest lateral pinnae, irregularly pinnatifid, glabrous, 4.5–5(7.5) × 3–4 cm near base, lateral pinnae 7.5–11.4 × 1.3–2 cm, lanceolate, serrate on both margins, asymmetric, basiscopic side at the base not serrate, long-acuminate, acumen up to 2.5 cm long. Veins dichotomously branched. Rachis brown, with few hair-like scales. Sori in two rows parallel to the midrib, so when mature, they seem to be confluent, broad elliptic, 0.5–0.7 × 0.25 mm, indusia not seen. Spores with reticulate perispore.

Etymology: —The species name ´ramicola` refers to the place where the new species has first been discovered, i.e, small branches in the canopy from a Pentadesma reyndersii (Clusiaceae) tree.

Distribution: — RWANDA. Southern Province: Nyungwe NP: Gisakura, Kamiranzovu.

Conservation assessment:—EOO: 41 km 2 which falls within the limits for Critically Endangered category; AOO: 12 km 2 which falls within the limits for the “Endangered” category. As the species occurs within a protected area, and therefore does not experience threat or decline, it cannot be assessed in any threat category; Therefore, it should be assessed as Least Concern (Protected area dependent).

Additional specimens examined (paratypes): — RWANDA. Western Province, Nyungwe NP, edge of Kamiranzovu swamp, 2000 m, 17 March 2022, E.Fischer, P.Ballings & B.Wursten s.n. (KOBL).

Ecology: —Canopy epiphyte. First found by chance in Nyungwe NP at Gisakura at the descent to the waterfalls at an elev. of 1953 m on a ca 30 m high fallen tree (Pentadesma reyndersii). A second locality was discovered near Karamba at km 100 on the road from Huye to Rusizi where Asplenium ramicola was growing on a mossy tree trunk at c. 10 m from the ground.

Note: – Asplenium friesiorum has very characteristic spores with a reticulate perispore with ecto-perispore forming a 3-dimensional lacy network with large openings exposing internal layers of meso- and endoperispore (Fig. 19, see above). We have examined six different specimens from D.R. Congo (Kahuzi-Biéga) and Rwanda (N Prov. to S Prov.) to check, if there is any morphological variation in the perispore ornamentation. As a result, we can show, that all spores are almost identical (Fig. 20). Also, the two populations of A. ramicola did not show any variation within the spores. So, we can conclude that this character is a good one to distinguish these species.