Inversodicraea tchoutoi Cheek, 2017

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 149-151

28. Inversodicraea tchoutoi Cheek , sp. nov. — Fig. 6

Similar to Inversodicraea ebo Cheek in the perennial, subshrubby, erect, highly branched habit;differing in that the ovaries and fruits lack apical wings, usually have 3 (not 2) stigmas, the leaflet margins have (5–)9–11(–16) equilaterally triangular teeth, not 8–14 linear divisions. — Type : Tchouto Peguy with Elad Maurice, Nnangah Austin 3378 (holotype K; isotypes KRI n.v., SCA n.v., WAG, YA n.v.), Cameroon, South Province (now Region), Campo Ma’an Area, Memve’ele waterfalls, N2°24' E10°21'48", alt. 360 m, fl., fr., 17 Jan. 2002 .

Ledermaniella cf. cristata sensu Ghogue (2011: 95) .

Etymology. Named for Dr. Peguy Gildas Tchouto, botanist and forester, formerly of the Mount Cameroon Project, later Professor at Mbalamayo For- estry School, now GTZ Biodiversity Adviser,Programme for the Sustainable Management of Natural Resources, Mount Cameroon.

Perennial, erect, subshrubby rheophytic herb, 4(–20) cm tall, repeatedly pseudodichotomously branched in the upper part forming flat-topped crowns 4.8–9 cm diam, with 40–90 ultimate branches. Root horizontal, narrowly ribbon-like (dorsiventrally flattened), adhering to substrate, 0.6–1.3 mm wide, lateral branches arising at (45–)70–90° from the main axis, at intervals of 1.2–5 mm. Stems arising at margin of root, opposite, sparse, developing a circular holdfast base to 4–12 mm diam, stem unbranched, terete, for 2–15 mm, 4–5 mm diam, surface wrinkled. Scale­leaves closely appressed and completely covering the upper part of the main axis and the ultimate stem branches, drying green, completely flat, papery in texture. Scale-leaves produced when underwater (when leaves are also present) are denser, with a low length: breadth ratio. Scale-leaves produced when plants emerged (leaves absent) are longer and less congested. Emerged scale-leaves are oblong-spatulate, 1.35–2(–2.5) by (0.4–)0.5–0.8(–1.3) mm, distal portion obtusely rounded in outline, and wider than the 0.3–0.5 mm wide proximal c. half which has entire, concave sides, the margin of distal portion with (5–)9–11(–16) ± regular equilaterally triangular subequal teeth, teeth dentate, 0.03–0.08(–0.1) mm long. Scale-leaves of the mid and lower part of the main axis with 5 % cover, semicircular, lacking well-developed lobes or teeth drying black, 0.8 by 0.9 mm, apex rounded. Leaves 2.2–8.3(–10) cm long, 5 times (or more) dichotomously branched, arising singly at the stem dichotomies; stipules absent; petiole flattened, at base, 0.5 mm wide, 0.9–3.5 cm long, narrowly ribbon-like, 0.5–0.75 mm wide, repeatedly dividing, gradually tapering to a point at apices. Spathellae arising at branch dichotomies, single, obovoid 1.1–1.3 mm long including the basal stipe c. 0.4 by 0.12 mm, partly concealed by the scale-leaves, mucro 0.1 mm long; the obovoid central portion 0.7–0.8 by 0.3–0.4 mm, dehiscing in c. 4 deep, irregular lobes, margins becoming involute. Flower pink (Tchouto 3378), erect. Pedicel 14–15 mm. Tepals 2, subulate, erect, 0.9–1 mm long. Stamens 2, shorter than gynoecium; united portion of filaments 1.5–1.7 mm long, free portions 1–1.1 mm long, the branches diverging at c. 90°. Anthers white, 1–1.1 by 0.35–0.4 mm pollen in monads, 0.03–0.038 mm diam. Gynophore 1.6 mm, dilating gradually at apex into the ovary. Ovary unilocular, fusiform 1.8–2.3 by 0.5(–0.7) mm, apex rounded-truncate. Stigmas 3, subulate, 0.65 mm long, gradually tapering to the apex, papillate, united at the base, spreading. Longitudinal ribs 6, equally prominent and spaced, the two commissural ribs much more weakly developed, with a central line of dehiscence. Fruit dehiscing into 2 equal, persistent valves, containing c. 40 seeds. Seeds ovoid, 0.25 by 0.07 mm, laterally flattened.

Distribution — Cameroon, South Region, Ntem River, known only from the Memv’ele Falls.

Habitat & Ecology — Waterfalls in the evergreen forest zone, with two wet and dry seasons. ‘Accroché en tapis sur rochers recouverts d’eau torrenteuse et cascadant. Abondant’. (Letouzey 10299); 350–450 m altitude. The species grows mixed with Ledermanniella bifurcata (e.g., Letouzey 15334).

Conservation — Since I. tchoutoi is only known from a single location, with an estimated AOO of 1 km 2 and with threats as cited under I. achoundongii and I. ntemensis , we here assess its conservation status as Critically Endangered, CR B1+2ab(iii).

Additional specimens. CAMEROON, South Region , Campo Ma’an Area , Boucle du Ntem, Around Meyas Ntem, N 2°20'80" E10°35'16", fr., alt. 480 m, 16 Feb. 2001, Tchouto 3170 (K, KRI n.v., SCA n.v., WAG); ibid., Memve’ele waterfalls, N2°24' E10°21'48", fr., alt. 360 m, 17 Jan. 2002, Tchouto 3376 (K, KRI n.v., SCA n.v., WAG, YA); ibid., 3377 (K, KRI n.v., SCA n.v., WAG, YA n.v.); ibid., 3378 (K, KRI n.v., SCA n.v., WAG, YA n.v.); ibid., Chutes du Ntem ou de Memve’ele prés Nyabessan (60 km E de Campo), st., 8 Apr. 1970, Letouzey 10299 (P00179253 image;P00179252 image);ibid., Chutes du Ntem prés de sa derivation sur la Bongola, 40 km ESE Campo, fl., 10 Dec. 1979, Letouzey 153399 (P00179268 image; P00179269 image; YA 3 sheets); ibid., fr., 21 Jan. 2016, Sene 1–15 (K, YA) ; ibid., 21 Jan. 2016, Sene 1–16 (K, YA) .

Notes — Using Cusset (1983, 1987), I. tchoutoi would key out as I. cristata . The species can be separated using the features in Table 2. Podostemologists working in Cameroon ( Koi et al. 2012, Schenk et al. 2015) appear to have referred to I. tchoutoi as I. (Ledermanniella) annithomae as discussed below and under the last species. Inversodicraea annithomae differs in having unbranched, floating, flexible stems which have short inflorescence shoots opposed to leaves at nodes, and constant internode lengths. It appears to be confined to the Ogouué River of Gabon.

The presence of three stigmas in I. tchoutoi otherwise only occurs within the genus in I. ntemensis , which, however, appears not to be particularly similar to I. tchoutoi . Horizontal gene transfer can be postulated, since they occur at the same site and both appear globally restricted to the Ntem River.

First collected in 1970 when sterile (Letouzey 10299), Cusset initially determined this specimen as I. cristata Engl. in June 1971, which is logical in view of the habit and the multiple dissections of the leaflet edge, albeit that these dissections are shallower and more triangular than those of that species. Consciousness of this may have led Cusset (1983) to rede- termine the specimen as paratype of I. annithomae which can have similar shallow multiple dissections. Cusset may have attributed the absence in Letouzey 10299 of the long, flexible flowing stems of I. annithomae as well as the great differences in inflorescence arrangement, to the juvenile, sterile state of Letouzey 10299.

Letouzey 15339 identified by Cusset in 1980, and published as paratype of Ledermanniella boumiensis ( Cusset 1983) is I. tchoutoi . There is no evidence that I. boumiensis occurs outside Gabon.

From Letouzey’s (10299) field notes and from the notes of Tchouto’s copious specimens, it appears that this species grows in colonies that cover rocks, like a green pile carpet, flowering mid December to mid January (leaves present), with fruits in mid February (leaves absent) and becoming sterile by mid April.

Figures

Fig. 6 Inversodicraea tchoutoi Cheek. a. Branched root, with base of perennial erect stems; b. distal portion of branching stems showing scale-leaves and leaves; c. detail of distal leaflet from b; d. detail of older leaflet from b; e. distal part of stem with unopened spathellae; f. detail of upper part of leaflet from e (base concealed by scale-leaves below); g. entire leaflet from e, including base; h. stem apices with flower at anthesis; i. detail of flower excluding pedicel, note the three styles; j. monad pollen grain; k. ovary, transverse section; l. fruit after dehiscence, inner surface of valves (all from Tchouto 3377, K). — Scale bars: a–b = 1 cm; c–g, i, k–l = 1 mm; h = 3 mm. — Drawn by Andrew Brown.