Inversodicraea ntemensis (Y.Kita, Koi, Rutish & M.Kato) J.J.Schenk, Herschlag & D.W.Thomas

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 142

21. Inversodicraea ntemensis (Y.Kita, Koi, Rutish & M.Kato) J.J.Schenk, Herschlag & D.W.Thomas

Inversodicraea ntemensis (Y.Kita, Koi, Rutish & M.Kato) J.J.Schenk, Herschlag & D.W.Thomas (in Schenk et al. (2015) 542). — Ledermanniella ntemensis Y.Kita, Koi, Rutish & M.Kato (in Kita et al. (2008) 224). — Type: R. Imaichi, Y. Kita & J­P. Ghogue CMR­65 (TNS), Cameroon, S. Region, rapids of Ntem River, 2 hr by motorboat from Campo beach, N2°14' E9°52', fl., fr., date unrecorded.

Ledermanniella bosii C. Cusset (1983) 385, p.p., quoad Letouzey 15333.

Etymology. Named for the Ntem River (also known as the Campo), the only known location for the species.

Distribution — Cameroon, S. Region, Ntem River, falls near Bongola at Memve’ele.

Habitat & Ecology — ‘On submerged or exposed rocks in waterfalls, only at Ntem waterfall … grows with Ledermanniella bifurcata (Engl.) C.Cusset’ ( Kita et al. 2008) and “sur rochers trés exposé aux embruns” (Letouzey 15333); c. 395 m altitude.

Conservation — Inversodicraea ntemensis is known only from the falls both at, and downstream of Memve’ele (a major hydroelectric project under construction, due for completion in 2017). Two additional hydroelectric streams are planned subsequently along the Ntem River (http://china.aiddata.org/ projects/289 downloaded 15 Feb. 2017), one of which is conjectured to be at Bongola itself. Sinohydro are constructing and China Exim Bank financing, the project. The area of occupation (AOO) is estimated as 1 km 2. The extent of occurrence (EOO) will slightly exceed the AOO. Given the single location and threat from the hydro project referred to, and EOO/AOO, we here assess this species using the IUCN (2012) standard as CR B1+ B2 ab(i,ii,iv) as Critically Endangered following broadly the assessment of CR B2 ab(iii) given by Cheek in Onana & Cheek (2011: 250). It is possible that this species will be rendered extinct by the construction and existence of the dam and its modification of seasonal water level changes of the river. The species is not listed on www.iucnredlist.org.

Additional specimens. CAMEROON, S. Region, Canon du Ntem , 30 km SW de Nyabessan, fl., 1 Dec. 1982, Nkongmeneck 420 ( YA) ; Ntem Waterfalls near Bongola, 40 km ESE of Campo, 10 Dec. 1979, R. Letouzey 15333 (P00179267 image, YA 3 sheets) ; Campo Ma’an area , Memve’ele Waterfalls N2°24' E10°21'48", fl., fr., 17 Jan.2002, Tchouto 3373 (K, KRI n.v., SCA n.v., WAG, YA) .

Note — Inversodicraea ntemensis , together with I. tchoutoi , also at Memve’ele, are alone in the genus for consistently having 3 (not 2) equal styles. Inversodicraea ntemensis is also unusual for the extremely sparse and inconspicuous scale-leaves which cover less than 5 % of the distal stems and which are reduced to short, narrowly triangular to ligulate structures that appear to be vestigial. The figure in the protologue depicts the scale-leaves occurring in whorls of three. The flowers are single, inserted in stem pseudo-dichotomies. Most of the bio- mass of the plants is comprised of the stout, branching stems and the numerous dichotomous leaves. This appears to be a perennial species. The species appears restricted to falls in the Ntem River above Campo, near Bongola, at Memve’ele.