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 22288 10.1007/s12225-022-10019-2 8482491c-b7d7-480e-bf86-3591d8193ca0 7599361 7. Saxicolella futa Cheek sp. nov. Type: Guinée ( Republic of Guinea ), Guinée Moyenne , Futa Djalon , Labé , Chutes de Salaa , 877 m alt., fr. 18 Jan. 2018 , Cheek 18973 ( holotype K [ K000592222 ]; isotype HNG ). http://www.ipni.org/urn:lsid:ipni.org:names:77297288-1 Sapicolella futa ined. Couch et al. (2019: 171 , 213) Annual herb , (1 –) 1.5 – 2 cm diam., stems including fruits 1.8 – 2.2 mm tall (Fig. 7A & B). Roots radiating, adhering strongly to substrate, dorsiventrally strongly flattened (thallus or ribbon-like), 0.2 – 0.5 (– 0.8) mm wide, internodes 1.5 – 2.2 mm long, repeatedly bifurcating at angles of 80 – 100 (– 120°), drying bright white, resembling Riccia (thalloid liverwort) (Fig. 8). Stems monomorphic, extremely short, in the fork of root bifurcations, bearing a sessile rosette, phyllotaxy spiral, leaves 2 – 3, spathellum single, terminal. Leaves concave, irregularly ovate or elliptic, 0.2 – 0.3 × 0.2 – 0.2 mm, apex acuminate, basal attachment broad, stipules absent, distal leaves larger than proximal. Spathellum pre-dehiscence ellipsoid, 0.3 × 0.25 mm, apiculate, basal part sheathed in leaves; dehiscing irregularly, then broadly funnel-shaped c. 1.2 × 0.8 mm. Pedicel erect, c. 0.6 mm long. Tepals 2, filiform, suberect, 0.2 mm long. Stamen one, filament 1.25 – 1.6 mm, erect, exceeding ovary; anther oblong, 0.18 – 0.2 × 0.18 mm, cells opposite. Gynoecium , gynophore curved, 0.6 × 0.1 mm. Ovary unilocular, ellipsoid in fruit, (0.7 –) 0.8 – 0.85 × 0.3 – 0.5 mm, elliptic in transverse section, c. 0.3 × 0.5 mm (Fig. 7H), with six shallow longitudinal ribs (commissural ribs not developed). Stigmas 2, complanate, oblong, 0.175 – 0.2 × 0.1 mm. Fruit placenta spindle-like (Fig. 7E). Seeds oblong-ellipsoid 0.25 × 0.18 – 0.19 mm (hydrated) (Fig. 7K). RECOGNITION . Differing from other Sapicolella species with sessile spathellae ( S. marginalis , S. deniseae ) in the shoots not marginal, numerous, closely spaced, but single, at root bifurcations; leaves lacking stipules (not stipulate); root slender (<1 mm wide, repeatedly and regularly bifurcating along its length (not>1 mm wide, not or rarely bifurcating along its length). DISTRIBUTION . Guinée (Republic of Guinea), Guinée Moyenne, Fouta Djalon. SPECIMENS EXAMINED. GUINEA . Fouta Djalon, Pita, above Chutes de Kinkon, 857 m alt. fl. 18 Jan. 2018, Cheek 18979 with Molmou (HNG, K [K000592222]); ibid 18 Jan. 2018, Cheek 18980 with Molmou (HNG, K [K000592223]); Pita, Chutes de Kambadga, 710 m alt. fr. 19 Jan. 2018, Cheek photo record; Labé, Chutes de Salaa, 877 m alt., fr. 18 Jan. 2018, Cheek 18973 (holotype K [K000592222]; isotype HNG). HABITAT . Waterfalls in the former cloud forest zone. The species grows at three sites each with several other Podostemaceae-Podostemoideae species (see case study above) but flowers, fruits and dies in advance of those, growing higher up in the riverbed than all other species of that group. 710 – 877 m alt. CONSERVATION STATUS . Known so far from three locations: 1) Chutes de Salaa near Dalaba (type locality); 2) above the Chutes de Kinkon; 2) Chutes de Kambadga, downstream of Kinkon. The AOO is estimated as 12 km 2 using the IUCN (2012) -preferred 2 km × 2 km grid cells and the extent of occurrence as 81.8 km 2 . Here Sapicolella futa is assessed as Endangered, EN B2ab(iii) since there are severe and imminent threats at all three locations. At locations 1) and 2) there are plans to build hydroelectric dams that are very likely to result in local extinction of the species (pers. obs. Cheek 2018 ). At site 2) the species is threatened by contamination of the water source by silt from run-off and by eutrophication due to contamination as the Kinkon river traverses the major town of Pita: fewer than 50 plants were seen at this location, and occupied a total area of <2 m × 2 m. In the next 10 years this species is expected to be reassessed as Critically Endangered (CR), or even “possibly extinct”. However, it is possible that further surveys may find additional sites for the species, which would be welcome. Seed banking and public awareness actions will be put in place as soon as possible. 1 Note added in proof May 2022: new imagery dated 21 Nov. 2021 shows the site completely submerged, extinction has likely resulted Fig. 7. Saxicolella futa . A habit; B three flowering or fruiting ► shoots at root terminal-bifurcations; C, D undehisced spathellum with shoot and root; E flower, part emerged from spathellum; F flower in spathellum, gynoecium removed, showing tepals, gynophore and stamen; G gynoecium; H ovary wall in transverse section showing ribs; J variation in stigmata; K seed, hydrated; L reconstruction of complete flower (based on E – G). A from photo by cheek at chute de Sal ’ aa. B – D, G – F from Cheek 18979. (K); E & F from Cheek 18980 (K). DRAWN BY ANDREW BROWN. PHENOLOGY . Presumably germinating no earlier than May, with the beginning of the wet season, before which its habitat is dry. Flowering may begin as early as November after the conclusion of the wet season in October. By January fruit has formed and the plants are dead. ETYMOLOGY . Named for the Futa (or Fouta) Djalon highlands of the Republic of Guinea to which the species appears to be unique. NOTES . Sapicolella futa has a shorter growing season, (possibly completing its life cycle in only six months or less) than all other Podostemaceae species present at each of the three locations at which it is known, apart from Tristicha trifaria . Both these two species were dead, dried and in fruit when encountered in Jan. 2018, while all other species of Podostemaceae present at these sites were still alive and only, for the most part, just becoming exposed by falling water and were in the process of beginning their flowering. The fact that, in these three locations, S. futa was found only on rock surfaces 20 – 100 cm above the waterlevel at which most other Podostemaceae (and all other Podostemoideae) occurred suggests that the species may have evolved into a niche to escape competition from those species. The extremely minute and inconspicuous stems, the diminutive ovaries, diminutive leaves, and slender roots in comparison with other species of the genus, may well all be reductions that have enabled it to occupy a niche where the growing season is short, being the last to be submerged, and the first exposed, of all the Podostemoideae niches present within its range. Sapicolella futa is unique in the genus for its very slender (<1 mm wide) ribbon-like roots, for the small size of its flowers, and for the position of the flowering shoots being only at the point of root bifurcations, so that the roots appear to terminate in a shoot before bifurcating. It is also unique in lacking evidence of stipules, but this is possibly concomitant with the reduction of leaf size. At maturity, more than 90 – 95% of the bulk of the plant consists of root, more so than any of the other species of the genus where the shoots are much more numerous and also larger and longer. The flowers and fruits are difficult to discern. Recent surveys in Guinea connected with the Guinea Tropical Important Plant Area programme (TIPAs) have discovered several other new species to science, all of which are threatened. Several of these are, like Sapicolella futa , also rheophytes, restricted to fast flowing water habitats, such as Inversodicraea pepehabai Cheek (Cheek & Haba 2016), I. koukoutamba and I. tassing ( Cheek et al. 2019a ) , Karima scarciesii (Scott Elliot) Cheek ( Cheek et al. 2016 ), Lebbiea grandiflora Cheek (Cheek & Lebbie 2018; Couch et al. 2019 ), while others are also found on the sandstone rock of the Fouta such as Keetia futa ( Cheek et al. 2018a ) , Calophyllum africanum (Cheek & Luke 2016), and Kindia gangan Cheek ( Cheek et al. 2018b ).