Asplenium markusbeckeri Eb.Fisch. & Lobin, 2023

Fischer, Eberhard & Lobin, Wolfram, 2023, Synoptic Revision of Aspleniaceae (Asplenium, Hymenasplenium) of Rwanda, Phytotaxa 608 (1), pp. 1-65 : 24

publication ID	https://doi.org/ 10.11646/phytotaxa.608.1.1
DOI	https://doi.org/10.5281/zenodo.8248998
persistent identifier	https://treatment.plazi.org/id/8D3A87D0-FFD6-5117-FF5D-FB7AFF9CBA51
treatment provided by	Plazi
scientific name	Asplenium markusbeckeri Eb.Fisch. & Lobin
status	sp. nov.

Treatment

Asplenium markusbeckeri Eb.Fisch. & Lobin View in CoL , sp. nov. ( Figs. 9–13 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 View FIGURE 13 ).

Holotype: —D.R. CONGO. Kivu, Idjwi Island, Fuwe , 2000 m, 12 September 1993, M.Becker 474 ( BR0000015253538 V, isotypes: B 20 0220604, B 20 022060, KOBL).

Diagnosis: —Morphologically similar to Asplenium gemmiferum Schrader (1818: 916) but differs in the constant lack of apical gemmae, and the pinna margins that are slightly to coarsely crenulate (subentire to minutely and regularly shallowly crenate in A. gemmiferum ). A. gemmiferum has rhizome scales 9–14 mm × 2–3 mm, lanceolate, attenuate, irregularly fimbriate, while A. markusbeckeri has smaller rhizome scales (5.26–7.74 mm × 1.21–1.82 mm) ( Fig. 12 View FIGURE 12 ).

The morphologically similar Asplenium ceii also lacks gemmae, but differs in having only 3–9 pinna pairs, distinctly crenulate pinna margins (slightly to coarsely crenulate in A. markusbeckeri ) and 10–15 sori pairs, vs. 16–27 in A. markusbeckeri .

The spores of Asplenium markusbeckeri have an alate ecto-perispore with reticulate meso-perispore bearing only few holes while the meso-perispore of A. gemmiferum is distinctly reticulate bearing numerous holes ( Fig. 13 E–F View FIGURE 13 ). The meso-perispore of Asplenium ceii is also distinctly reticulate and similar to that of A. gemmiferum .

The Southern African Asplenium prionitis Kunze (1836: 511) also lacks gemmae. It differs from A. markusbeckeri in the rhizome scales 8 mm long, the pinnae in 6 pairs, with margin sharply serrate-dentate, and the pinnae sharply attenuate (tapering into an attenuate apex in A. markusbeckeri ).

Description: —Terrestrial or epiphytic, 60–120 cm tall. Rhizome erect, to 20 mm diameter with brown to black, lanceolate acuminate irregularly fimbriate rhizome-scales, 5.26–7.74 × 1.21–1.82 mm, composed of thin-walled cells. Fronds tufted, arching, somewhat fleshy, to 80 cm long. Stipes matte grey to brown above and green below, canaliculate, 22–30 cm long and 3 mm diameter, at first densely clothed with subulate clathrate subentire or fimbriate scales, gradually becoming subglabrous. Lamina oblong-lanceolate, 1-pinnate, 40–100 ×(30–) 34–40 cm. Pinnae in 7–9 pairs, alternate, coriaceous when fresh, dark green and shiny above, lanceolate to narrowly elliptic, 1–20 × 3.8– 4.8 cm at base, petiolate, petiole 9–17 mm long, unequally cuneate at the base with the acroscopic base parallel to the rachis and the basiscopic one cuneate, up to 2.5 cm long, margin slightly to coarsely crenulate, tapering into an acuminate apex, glabrous or nearly so; basal pinnae slightly reduced, terminal pinna similar to other pinnae. Veins forked. Sori equally spread along the veins at 45° to midrib, 16–27 pairs, usually extending from near the costa almost to the margin; indusia linear membranous, entire, ± 1 mm wide. Spores with alate ecto-perispore with reticulate meso-perispore bearing only few holes

Etymology: —The species name refers to Markus Becker, who studied the ferns of Kahuzi-Biéga National Park and Idjwi Island in his Master thesis in 1993. He already wrote: „Vorkommen scheint auf einzigen Fundort beschränkt zu sein; mit hoher Wahrscheinlichkeit neue Art“ (the distribution seems to be restricted to one locality, with high probability a new species).

Habitat: —Terrestrial or epiphyte on lower mossy branches in montane rainforest, elev. 1625 m in Rwanda, 2000 m in D.R. Congo.

Distribution in Rwanda:—Northern Province: Volcano NP, Ibuhanga Forest.

General distribution: —D.R. Congo, summit area of Idjwi Island; Rwanda, Ibuhanga Forest.

Additional specimen seen (Paratype):— Northern Province: Volcano NP, Ibuhanga Forest , epiphyte in submontane forest on lava rocks, 1625 m, S1°34`12.56`` E29°38`08.17``, 30 March 2009, E.Fischer s.n. ( KOBL) GoogleMaps .

Conservation Status: —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. One collecting site is situated outside any protected area, and is under great threat of montane forest habitat loss which is the result of increasing human population pressure on the environment.