Saxicolella ijim Cheek

Cheek, Martin, Molmou, Denise, Magassouba, Sekou & Ghogue, Jean-Paul, 2022, Taxonomic revision of Saxicolella (Podostemaceae), African waterfall plants highly threatened by Hydro-Electric projects, Kew Bulletin 77 (2), pp. 403-433 : 411-415

2. Saxicolella ijim Cheek sp. nov.

Type: Cameroon, North West Region, Bamenda-Fundong , Anyajua , “ Waterfall near Ijim Project HQ ”, fl. fr., 12 Dec. 1998, Cheek et al. 9920 (holotype K [ K000229622 ]; isotypes SCA, YA ).

http://www.ipni.org/urn:lsid:ipni.org:names:77297282-1

Ledermanniella cf. musciformis sensu Cheek ( Cheek et al. 2000: 69, 152)

Perennial or annual herb, rosette-like, 7 – 8 cm diam. Root crustose in the central part of the plant, at the edge radiating and divided into separate, free, lobes, 0.5 – 0.8 cm wide (Fig. 2A). Stems (1 –) 2 – 6, arising from the crustose centre of the root rosette (absent from the radiating lobes), erect, free-standing, branched from the base, (1 –) 3 – 7 cm tall, spreading as wide as the root rosette, terete, each c. 2 mm diam. at base, with 3 – 8, ± evenly spaced, short leafy side-branches (Fig. 2B), proximal branches up to 1.5 cm long, phyllotaxy spiral, diam. slightly more slender than the principal axes, leaves with axillary rosette shoots. Rosette (spur) shoots axillary with stems inconspicuous, 1 – 2 per axil, each bearing 2 – 8 leaves and a single terminal spathellum. Leaves of side branches withspiral phyllotaxy, internodes c. 1 mm long, laterally compressed, linear, (2 –) 2.5 – 8 × 0.25 mm, entire, very rarely bifid, apex obtuse-rounded, basal 1 – 2 mm canaliculate, shortly sheathing the stem, astipulate (Fig. 2B), subtending axillary rosette shoots. Leaves of rosette shoots, proximal leaves as those of the subtending sidebranches, but usually with a pair of stipules arising from near base of the leaf sheath; distal 1 – 2 leaves immediately subtending the spathellum usually astipulate, shorter, 1.5 – 2 × 0.3 mm (Fig. 2D). Stipules symmetrical, equal, on each side of the leaf, narrowly triangular, 0.1 – 0.5 (– 0.8) × 0.1 mm, apex rounded, size of stipules increasing towards stem apex-spathellum (Fig. 2C). Spathellum (undehisced) orbicular, 1 mm diam., mucro 0.2 mm long with apex rounded; dehiscing irregularly, post-dehiscence 1 – 2 × 0.7 – 1 mm (Fig. 2D). Flower ± erect in bud (in spathellum); at anthesis partly included in the ruptured spathellum (Fig. 2E – G). Pedicel 0.5 – 1.5 mm long at anthesis. Tepals 2, slightly spatulate-oblanceolate to filiform 0.2 – 0.3 mm, distal portion 0.1 mm broad, flat, stipe 0.05 mm broad, erect (Fig. 2F & G). Stamen as long as or exceeding gynoecium, filament 1 – 1.2 mm long, dorsiventrally flattened; anther oblong 0.5 × 0.25 mm. Gynophore 0 (– 0.2) mm long. Ovary ellipsoid 0.75 – 1 × 0.6 – 0.65 × 0.7 – 0.75 mm, in transverse section slightly ellipsoid, slightly narrower along the sutured plane; unilocular, longitudinal ribs well-defined, 6 (three on each valve), commissural ribs absent (Fig. 2J). Stigmas 2, complanate, ovate, 0.25 – 0.3 × 0.18 – 0.2 mm, minutely verrucate (Fig. 2E – H). Fruit about same size as ovary; pedicel accrescent (1.5 –) 2.5 mm long, carrying fruit beyond the spathellum (Fig. 2H). Seeds ellipsoid 0.2 × 0.15 mm.

DISTRIBUTION. Cameroon, North West Region, Bamenda-Fundong, Anyajua, known only from the type locality.

SPECIMENS EXAMINED. CAMEROON, North West Region, Bamenda-Fundong, Anyajua, “Waterfall near Ijim Project HQ”, fl. fr., 12 Dec. 1998, Cheek et al. 9920

(holotype K [K000229622]; isotypes SCA, YA). Only the type specimen is known.

HABITAT. On boulders in spray zone below waterfall from basalt cliff, in former submontane forest belt. No other Podostemaceae present (Cheek pers. obs. Dec. 1998); 1200 m alt.

CONSERVATION STATUS. Sapicolella ijim is known from a single waterfall, with only 20 – 30 plants scattered in an area of not more than 10 m × 10 m. Threats were not apparent at the time of collection. Here the species is assessed as Critically Endangered, CR B2ab(iii)+D. The waterfall is fed from a stream at the top of the Ijim Plateau where cattle have been introduced, posing a threat by their grazing and trampling increasing surface run-off and so silt levels in the stream feeding the falls. Targeted searches for Podostemaceae at numerous other waterfalls in the Fundong-Anyajua -Ijim area in 1998 did not uncover any additional sites for this species ( Cheek et al. 1997; Cheek et al. 2000). Targeted searches by Ghogue to refind this taxon (then thought to be Ledermanniella musciformis ) in the Bamenda area in 2006 with Ryoko Imachi and Yoko Kita failed to find it. Nearcomprehensive botanical surveys in other locations S, Wand Eof Kilum-Ijim have failed to find additional locations although they brought to light several other species of Podostemaceae (e.g. Cable & Cheek 1998; Chapman & Chapman 2001; Harvey et al. 2003, 2010; Cheek et al. 2003, 2010, 2011).

PHENOLOGY. Flowering and fruiting in December, 2 – 2 months after the end of the main wet season.

ETYMOLOGY. Named for Ijim, tribal lands of the Kom people, to which area this species is unique on current evidence.

NOTES. When revisiting an incomplete and unsatisfactory identification the first author had made of a specimen from the Fondom of Kom in the Bamenda Highlands of Cameroon many years ago (Cheek 9920, Ijim, Anyajua, waterfall, 1200 m, 12 Dec. 1998, previously identified as Ledermanniella cf. musciformis: Cheek et al. 2000: 152 ) it was realised that the fruiting ovary was erect emerging from the spathellum and, given the ribbon-like roots, longitudinally ribbed fruit and single stamen, that this could not possibly be a Ledermanniella , but a species of Sapicolella .

Prior to this paper, the only other published species of Sapicolella sensu stricto known which has long stems was S. flabellata . Sapicolella ijim differs from S. flabellata in the simple leaves, very rarely bifid (not flabellate, quadrifid); stigmas complanate, ovate (not filiform); fruit 6-ribbed, ellipsoid, length:breadth ratio c. 1: 0.65 (not 8-ribbed, fusiform, length: breadth c. 1: 0.22).

Sapicolella ijim occurs within a few kilometres of S. marginalis . These two species, together with S. angola , occur at the highest altitudes known for the genus (1200 – 1300 m alt.). The two Bamenda Highland species are easily separated since while the first has long stems, which are only produced from the centre of the radiating root rosette, the second lacks long stems completely, and instead bears numerous sessile, rosette-like stems along the margins of the radiating ribbon-like roots.

Sapicolella ijim is similar to Sapicolella sp. Ain the unusual feature of the ovary being sessile (the gynophore being absent).

Asummary of the rare, high altitude plant species of Kilum-Ijim (Mt Oku) is given by Maisels et al. (2000). Additional narrowly endemic species discovered from the Kilum-Ijim area are: Ternstroemia cameroonensis Cheek ( Cheek et al. 2017c), Dovyalis cameroonensis Cheek (Cheek & Ngolan 2006).