Taxonomic revision of Saxicolella (Podostemaceae), African waterfall plants highly threatened by Hydro-Electric projects Author Cheek, Martin Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AE, UK. m.cheek@kew.org Author Molmou, Denise Herbier National de Guineé, Université de Gamal Abdel Nasser, BP 680, Conakry, République de Guinée. Author Magassouba, Sekou Herbier National de Guineé, Université de Gamal Abdel Nasser, BP 680, Conakry, République de Guinée. Author Ghogue, Jean-Paul Green Connexion, PO Box 1289, Yaoundé, Cameroon & IRAD-National Herbarium of Cameroon Yaoundé, PO Box 1601, Yaoundé, Cameroon. text Kew Bulletin 2022 2022-05-30 77 2 403 433 http://dx.doi.org/10.1007/s12225-022-10019-2 journal article 10.1007/s12225-022-10019-2 1. Saxicolella flabellata ( G.Taylor ) C.Cusset (1987: 93); Onana & Cheek (2011: 252 – 252) ; Onana (2011: 116) ; Onana (2012: 137) all pro parte . Type: Nigeria , Ogoja , Aboabom- Boje path crossing the Afi R. , fl. fr. 12 Dec. 1950 , Keay FHI 28230 ( holotype BM , isotype K [ K000325201 ]). Pohliella flabellata G. Taylor (1952: 52 ; 1953: 123 ). Perennial herb (probably) with stems to c. 20 cm long, floating on surface of water when flowering. Roots green blotched red, ribbon-like, bearing both short shoots with sessile spathellae and long-stemmed shoots. Stems of long shoots terete, c. 2 mm diam., divided, internodes of principal axis 3.5 – 27 mm long. Leaves heteromorphic, leaves of long stems flabellate or dichotomously divided to 5 times, to 2 × 2 cm, ultimate segments capillary, base subpetiolate, sheathing, stipules absent. Leaves of short shoots s ubtending root-borne spathellae 2 – 2, spirally inserted, outermost two leaves scale-like, sheathing, triangular-ovate or quadrate, slightly concave, 0.25 – 0.5 × 0.2 mm, second leaf longer than first; third leaf linear, 1 – 2.75 cm × 0.05 mm, apex obtuse, sometimes bifurcate. Spathellae in clusters of (1 –) 2 – 3 (– 5) either sessile on root or in leaf axils, cylindrical to narrowly ellipsoid (1.1 –) 1.3 – 1.5 × 0.25 mm, apex obtuse, dehiscing at apex only. Flower at anthesis with ovary concealed within spathellum, only the styles and stamen exsert- ed. Pedicel minute, 0 – 0.2 mm long. Tepals 2, subulate, 0.2 – 0.5 mm long. Staminal filament 3 – 3.5 mm long. Anther quadrate 0.5 – 0.75 × 0.5 mm, latrorse, pollen in dyads. Gynophore 0.2 – 0.25 mm long. Ovary ellipsoid to fusiform, 2.25 – 2.5 × 0.9 – 1 mm, with 8 longitudinal lines. Stigmas 2, filiform, 2 mm long. Fruit capsule ellipsoid, 2.5 × 0.75 mm, 8-ribbed, 2-valved. Seeds ellipsoid 0.25 × 0.15 mm (Fig. 1). DISTRIBUTION . Nigeria, Cross River State, only known from the Afi River Forest Reserve near Ikom. SPECIMENS EXAMINED . NIGERIA . Cross River State , Ogoja , Aboabom- Boje path crossing the Afi R., fl. fr. 12 Dec. 1950 , Keay FHI 28230 ( holotype BM , isotype K [ K000325201 ]) (only known from the type specimen). HABITAT . River falls in evergreen forest, with Ledermanniella tenuifolia (G.Taylor) C.Cusset ( Taylor 1953: 127 re Keay in FHI 28231). c. 112 m alt. CONSERVATION STATUS . Ouedraogo (2010) assessed the conservation status of Sapicolella flabellata as Data Deficient in 2008, stating that there are records from Cameroon, Ghana, Niger and Nigeria. However, no records have been found from either Niger or Ghana and this seems most unlikely. Independently, on the basis of a location in Nigeria and one in Cameroon, Onana & Cheek (2011: 252 – 252) assessed the species as EN B2ab(iii). Kuetegue et al. (2019) also assess the species as EN B2ab(iii) citing no new data. Cusset (1987) had erroneously identified Thomas 2653 (K, MO, P, YA) collected 9 Dec. 1982 from Korup, Cameroon as this species, but this was corrected by Cheek (2020) to Pohliella laciniata . In fact, S. flabellata remains known only from the type collection made by Keay in Dec. 1950 on a footpath across the Afi River in what is today the Afi River Forest Reserve of Nigeria. Reviewing Google Earth imagery for the site (placed at 6°15ˈ28.6"N, 9°00ˈ32.71"E, elev. 112 m, viewed June 2021) shows that the footpath has been upgraded to a motor road, and that clearing of the forest canopy is steadily taking place, confirming a report that dates from 6 Jan. 2016 and shows oil palm plantations, and open canopies indicative of logging, and these are confirmed by on-the-ground reports (https:// www.pandrillus.org/projects/afi- mountain-wildlifesanctuary/). Surface run-off due to these activities may have contributed to the extensive sediment deposits in the river that appear to be visible when the river is viewed by satellite imagery. Siltation of rivers is known to pose a threat to Podostemaceae ( Cheek et al. 2017b ) . Therefore, we assess S. flabellata here as Critically Endangered CR B1+B2ab(i-iv), estimating the AOO and EOO as 3 km 2 using this cell-size as preferred by IUCN. PHENOLOGY . Flowering and fruiting in mid-December. ETYMOLOGY . Referring to the shape of the leaves, flabellate meaning fan-shaped. NOTES . Distinct from all other known species of the genus in the very long stems, and in bearing spathellae from dimorphic leaved shoots, those arising from the roots being different from those from the long stems. Similar to Sapicolella angola in the spathellae in terminal clusters, not single, and subtended by more or less flabellate leaf rosettes. Originally described by Taylor as a Pohliella , he explained that he was in a quandary as to placement in this genus or in Sapicolella as described by Engler (1926) which work he criticised (“I am not satisfied that the key characters used by Engler are sufficiently diagnostic”). In fact, Engler had separated these two genera in his key ( Engler 1920: 29 ) based on locule number, and fruit rib number although they differ in other features. Taylor based his placement on features other than those in Engler’ s key (“I have placed it in this genus due to the subulate stigmas and dichotomous leaves”), despite the first being discordant (“it deviates from the generic description in having a unilocular ovary”) ( Taylor 1952: 55 ). It seems from the molecular phylogenetic evidence of Koi et al. (2012) that in this case locularity is indeed a better indication of relationships than leaf habit and stigma shape. Sapicolella submersa (J.B.Hall) C.D.K.Cook & Rutish. is superficially very similar to Pohliella laciniata which grows in the same area at the forest border of Cameroon and Nigeria. Both species flower from long stems when these reach the water surface as the levels drop in the drier season. That both species have clusters of several flowers surrounded by rosettes of flabellate leaves that form a protective funnel, borne on long stems may be convergence to this scenario. These rosettes may function to float on the surface and protect the flowers they contain from water droplets (observed by the first author for Pohliella laciniata in Cameroon). The same trait (several flowers surrounded by a rosette of flabellate leaves) is seen otherwise seen only in Sapicolella angola where the ecology is unreported and the specimens fragmentary. Other species of Sapicolella have single flowers borne terminally in rosettes of leaves that are linear or highly reduced and can have no protective function during flowering (although they are likely to protect the developing flower buds). Other species are also both confined to the forest of the Afi River Forest Reserve and adjoining Cross River forests in SE Nigeria and known from only one or two collections, e.g. Anchomanes nigritianus Rendle ( Moxon-Holt & Cheek 2021 ) and Talbotiella eketensis Baker f. ( Mackinder et al. 2010 ).