Asplenium uschiae Eb.Fisch. & Lobin, 2023

Fischer, Eberhard & Lobin, Wolfram, 2023, Synoptic Revision of Aspleniaceae (Asplenium, Hymenasplenium) of Rwanda, Phytotaxa 608 (1), pp. 1-65 : 50

publication ID	https://doi.org/ 10.11646/phytotaxa.608.1.1
DOI	https://doi.org/10.5281/zenodo.8249078
persistent identifier	https://treatment.plazi.org/id/8D3A87D0-FFF0-5131-FF5D-FA92FEC2BB5D
treatment provided by	Plazi
scientific name	Asplenium uschiae Eb.Fisch. & Lobin
status	sp. nov.

Treatment

Asplenium uschiae Eb.Fisch. & Lobin View in CoL , sp. nov. ( Figs. 26–29 View FIGURE 26 View FIGURE 27 View FIGURE 28 View FIGURE 29 ).

Holotype: — RWANDA. Western Province : Nyungwe NP, Cyamudongo Forest, forest floor, elev. 1889 m, 4 April 2021, S2°33`21.65`` E28°59`09.12``, E.Fischer s.n. ( BR0000015253552 V!; isotypes: B 20 0220600!, KOBL!). GoogleMaps

Diagnosis: — Asplenium uschiae differs from A. christii in the higher dissection of the lamina. The new species has a 1-pinnate-pinnatisect lamina, Laminae 1-pinnate-pinnatisect to partially gradually tapering from the base. The largest pinnae are deeply pinnatifid to pinnatisect (mostly incised 2/3 towards the costa) with the basal acroscopic segment being an enlarged free ovate lobe, segment margins entire to coarsely crenate while the lamina in A. christii is 1-pinnate with entire pinnae with margin serrate to sharply crenate and the pinnules never separated from the costa.

Asplenium bugoiense , A. preussii and A. udzungwense Beentje (2008: 41) differ in higher dissection of the laminae (lamina 2-pinnatifid to 3-pinnatifid vs. 1-pinnate-pinnatisect in A. uschiae ). In Asplenium bugoiense the lower acroscopic pinnule is much larger than the remaining pinnules, with 4–5 teeth, at least the 2–3 adjacent pinnules also pinnate, with usu. 3 teeth. In A. uschiae the lower acroscopic pinnule is only slightly larger and shallowly dentate, the adjacent lobes are bifid at apex and incised to ½–⅔ to the costa.

In Asplenium preussii the lower acroscopic pinnules are much larger than the remaining pinnules, only the basal acroscopic pinnule is lobed, the adjacent pinnules are linear-lanceolate, unlobed or only slightly lobed at apex.

In Asplenium udzungwense the lamina is 2-pinnatifid to 3-pinnatifid, with pinnae ovate, obtuse, with a single large acroscopic lobe slightly 2–3-lobed at apex, the main pinna crenate to almost lobed with teeth to 2 mm.

Description: —Terrestrial fern. Rhizomes erect, covered with scales; scales ovate-lanceolate, apex elongate, margins entire, maroon-colored, 3.2–5.46 × 0.92–1.57 mm, widest in lower third, the cells in the center becoming darker to the middle and have thicker walls ( Fig. 29 View FIGURE 29 ). Fronds spaced. Stipes (14–)26–32(–35.7) cm, furrowed, greenish when young, becoming pale brown with age, sparsely covered with scales, scales in the lower part similar to those from the rhizome, towards the rachis lanceolate, 2.73 × 0.53–0.7 mm, at their base with maroon-colored appendages, 0.27–0.76 × 0.04–0.06 mm ( Fig. 29 G, H View FIGURE 29 ). Lamina lanceolate, (31–)35–62 × 10.4–14.5 cm, 1-pinnate, 1-pinnatifid. Pinnae with (1–)19–22 pairs, opposite to subopposite, alternate towards the apex, lanceolate, 6.1–8.2(–10) × (1.8)2.1– 3.1(–3.9) cm, the lowermost slightly smaller, tapering towards the apex, proliferous at the base of terminal pinna. Pinnae with the basic acroscopic pinnule ovate, enlarged, totally separated from the secondary rachis, towards the apex pinnules incised from 30–60%, (1.2–)1.4–2.2(–2.5) × 0.6–1.3 mm. Rachis pale brown, greenish towards apex, sparsely covered with scales; scales lanceolate, 1.74–1.89 × 0.26–0.34 mm, at the base with appendages 0.27–0.76 × 0.04–0.06 mm, cells elongate, rather uniform. Sori (6–)8–11(–12) per pinnae, linear, located on acroscopic vein of pinnae lobes, 4.5 × 0.33 mm; indusia linear, 5.2–5.75(–7.02) × 0.35–0.75 mm, transparent. Spores not seen.

Etymology: —Dedicated to Uschi Lobin, wife of the second author.

Distribution: —D.R. Congo (Idjwi Island), Rwanda (Cyamudongo Forest).

Conservation assessment: —With only two collecting sites, it is not possible to calculate an Extent of Occurrence (EOO). EOO: not applicable; AOO: 8 km 2. The area of occupancy (AOO) falls within the limits for the Critically Endangered category.

Additional specimen examined (paratype): — D.R. CONGO. Kivu, Idwi-Island, Langira-Modusa , c. 2040 m, August 1993, M.Becker 467 ( KOBL) .

Ecology: —Forest floor in dense montane forests, elev. 1889–2040 m in Rwanda and D.R. Congo.

Notes: —Despite the large and uniform population at the type locality in Cyamudongo Forest covering hundreds of square meters, no mature spores were observed. It cannot be excluded that the species is of hybridogenous origin with Asplenium christii , A. bugoiense or A. preussii as the potential parents also occurring in Cyamudongo Forest.