Inversodicraea eladii Cheek, 2017

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 151-153

29. Inversodicraea eladii Cheek , sp. nov. — Fig. 7

Inversodicraea eladii (Fig. 7) has its closest affinity with two species, I. bosii (see Table 3 for differences), which occurs at the same locality, and I. congolana which occurs at the other side of the Congo basin. The first lacks the distinctive apical 2-winged ovary-fruit of I. eladii , and also differs in the scale-leaves being mostly (> 90 %) ovate;the proximal half of the stems being naked of scale-leaves; the leaves being 1-dichotomous. In I. eladii the scale-leaves are mainly triangular or with 1–2 small lateral triangular lobes (apart from subulate scale-leaves near the spathellae) and the stems have a c. 5 % covering of scale-leaves;the leaves are many-times dichotomously branched. Inversodicraea congolana closely resembles I. eladii in the apically 2-winged ovary and fruits. However, the fruits of I. eladii are 6-ribbed, not 8-ribbed as in I. congolana . Further, the leaves are only dichotomous (not 4–5-times dichotomous), the habit only 0.5–1.5 cm tall, not 6–10 cm tall. — Type: Elad Maurice with Tchouto Peguy 1485A (holotype K; isotypes KRI, WAG, YA), Cameroon, South Region, Camp Ma’an area, Lobe, Lobe Waterfalls in Grand Batanga area at the edge of the sea, N2°52'57" E9°53'50", fl., alt 5 m, 30 Nov. 2001.

Rheophytic herb, probably annual, root not recorded; stems erect, free-standing, highly branched, 6–10 cm tall, terete, 1–1.9 mm diam at base, each stem arising from rock with 30–50 ultimate branches. Scale­leaves on main stem and branches (below the distal 3–6 mm) wrinkled, naked apart from c. 5 % cover of narrowly to equilaterally triangular (rarely slightly lobed), partly spreading scale-leaves 0.25–0.5 by 0.2–0.4 mm. Distal 3–6 mm ± completely covered in scale-leaves, scale-leaves narrowly triangular, 1–1.25 by 0.28–0.4 mm, apex acute, margin entire, at about 10 % of scale-leaves with a deep lateral division or bifurcation, sometimes with two shallow, unequal lateral triangular divisions each 0.02–0.15 mm long, which one greatly smaller than the central lobe, these 2-lobed scale-leaves most common in the interstitial zone between the densely covered distil 3–6 mm of the branches, and the 5 % sparsely covered lower branches and main stems. Leaves 1.6–5 cm long, arising laterally, 4–5-times dichotomously branched, rarely a single, scale-leaf-like lobe near bases of younger leaves, triangular, 0.25– 0.1 mm, placed on the petiole margin up to 0.7 mm from the base; petiole 0.9–3.2 cm long dorsiventrally flattened, 0.4–1.5 mm wide (widest in the older leaves produced on the main axis); blade ribbon-like (dorsiventrally flattened), 0.5–0.8 mm wide, tapering gradually to the acute apices. Spathellae inserted at stem dichotomies, single, obovoid-cylindric 2.5–3.2 by 1 mm, apex rounded, base concealed among scale-leaves, cylindric; opening irregularly into 3–5-deep, integral lobes. Pedicel 8.5–9(–10) mm long. Tepals 2, linear, 0.75–0.8(–1.1) mm long, inserted at new base of androecium. Androecium exceeding gynoecium, c. 5 mm long, anthers 2; united filaments 1–2 mm long, free filaments diverging by c. 20–45°, 2–3 mm long. Anthers subtriangular, 1–1.25 by 0.3 mm. Pollen in dyads, long axis 0.05 mm long. Gynophore 0.3–0.5 mm long, dilating gradually to base of ovary. Ovary unilocular, narrowly cylindrical-ellipsoid 2.5–2.7 by 0.6–0.75 mm. Styles 2, erect, narrowly subulate, 0.75–1.1 by 0.05 mm wide at base, sometimes united in the proximal 0.2 mm. Longitudinal ribs 8, subequal in spacing and development, the two submedial ribs on each side united by a triangular or rounded membranous protrusion, making the ovary apex 2-winged; commissural ribs each with a sutural groove. Fruit dehiscing by two valves, not caducous. Seeds not recorded.

Distribution — Cameroon, South Region, Lobé river at Lobé Falls.

Habitat & Ecology — Rheophyte on rocks in waterfall near the sea, in evergreen forest zone; 5 m altitude.

Conservation — Inversodicraea eladii is known from a single location, the Lobé Falls, at which we assess its AOO (and so its EOO) as 1 km 2 using the IUCN-preferred cells of that size. Here, as is the case for I. bosii , similarly restricted to this location, it is threatened by trampling from the many tourists that visit what in Cameroon is a major tourist attraction (Cheek in Onana & Cheek 2011, Ghogue 2011). Therefore the species is here assessed as Critically Endangered, CR B2 ab(iii).

Notes — Ovary wings are rare in the genus. Otherwise they are only known in I. ebo , I. congolana , and I. warmingiana , the last with a triangular wing from the apex of all six longitudinal ribs. Only in I. eladii and I. ebo of Cameroon do the wings appear to connect more than one rib on each valve of the ovary. Distal (and also lateral) ovary wings are highly developed in the genus Winklerella Engl. In fact this appears to be the only character supporting recognition of that genus, leading us to question whether this distinction is merited or not.

Near the base of three young leaves, a single lobe, similar to a scale-leaf, was noted. Initially, these were taken to be stipular lobes, but since each leaf has only one such lobe and not a pair, and since they are not present on most leaves, this has been ruled out.

Hybridisation — The type collection Elad 1485A was mixed (Kew sheet) with an equal amount of sterile I. ledermannii (Elad 1485) which superficially looked very similar, but which was identified by its scale-leaves being broadest in the distal half, and equally, and deeply acutely trilobed. That I. eladii was in flower while the I. ledermannii had not yet developed spathellae suggests that the first flowers in advance of the second, which suggests reproductive separation of the two species. Nevertheless, specimens from this same locality (Elad 1482, 1484) appear to be intermediate between these two species in leaflet shape, the scale-leaves being long and slender, as in I. eladii , but with c. 50 % divided at the apex into three subequal, but not spreading, lobes. These plants may represent hybrids between the two species.