Inversodicraea nicolasii (C.Cusset) E.Bidault, Rutish. & Mesterhazy, 2023

Bidault, Ehoarn, Boupoya, Archange, Ikabanga, Davy U., Nguimbit, Igor, Texier, Nicolas, Rutishauser, Rolf, Mesterhazy, Attila & Stevart, Tariq, 2023, Novitates Gabonenses 93: a fresh look at Podostemaceae in Gabon following recent inventories, with a new combination for Ledermanniella nicolasii, Plant Ecology and Evolution 156 (1), pp. 59-84 : 59

Inversodicraea nicolasii (C.Cusset) E.Bidault, Rutish. & Mesterhazy comb. nov.

Figs 3D, E , 4B , 5

Ledermanniella nicolasii C.Cusset, Bulletin du Muséum National d’Histoire Naturelle, Section B, Adansonia. sér. 4, Botanique Phytochimie 6(3): 274. ( Cusset 1984: 274)

Type.

GABON • Ogooue river at Booué ["Lit de l’Ogooué à Booué”]; 29 Jul. 1966; [0°05 ’24” S 11°55 ’59” E]; 165 m; fl., fr.; N. Hallé & A. Le Thomas 205; holotype: P [P00179341]; isotypes: P [P00179342, P00179343] .

Distribution.

Endemic to the Ogooué and Ivindo rivers, in Gabon. Before 2017, this species was only known from a single collection made at Booué rapids on the Ogooué. In 2018, it was discovered on the Kongou falls, on the Ivindo river. In 2019, it was discovered on the Touné falls on the Ivindo river, less than 4 km upstream from the confluence with the Ogooué river, 30 km east of the type locality at Booué, and ca 60 km south-west of the Kongou falls. Recent efforts of Podostemaceae inventory at Booué rapids (west of the city) allowed for the rediscovery of this species at its type locality. Nevertheless, it seems very rare at this site, since only one of the 70 collections made at this site between 2019 and 2021 represents this species. Given the considerable size of the rapids area, which is not yet fully explored, it is possibly more abundant than suggested by our data. The type material collected in 1966 includes a lot of individuals, suggesting that the species was, at least then, abundant on site. A natural, partial replacement of this population by another species cannot be excluded.

Habitat and ecology.

Rapids and falls in large rivers from ca 100 to 500 m wide, 165-425 m in elevation. It appears to be quite abundant at Kongou falls, but rare at Booué and Touné falls. Flowers and fruits were collected in February, July, and August. The species grows intermingled with Ledermanniella schlechteri and Macropodiella hallaei at the Kongou falls. It appears to grow with M. hallaei , M. heteromorpha , and L. pusilla at the Touné falls. It was collected in micro-habitats submitted to strong currents. It is apparently consumed as a vegetable by local people around the Kongou falls in Gabon (boiled in water). Recent footage taken from the Kongou falls also showed an elephant potentially feeding on Podostemaceae , even though it is unclear if this species in particular is targeted.

Notes.

The recent material collected at Kongou falls on the Ivindo river revealed the presence of few, small but conspicuous triangular to wart-like, patent stem scales, most of them with a distal black dot, mostly grouped below the inflorescences, and very scarce along the stem. Closer examination of the type collection revealed similar stem-scales that were overlooked by Cusset, who initially placed this species in subgenus Ledermanniella rather than subgenus Ledermanniella Phyllosoma . Because of the presence of clear stem-scales, we consider that this taxon belongs to the genus Inversodicraea . The recent collections from the Ivindo river show minor differences with the type collection, such as shorter and wider leaves and longer flowers and capsule stalks (up to 3 cm long vs up to 2 cm long), ca 60% of them bearing 3 stamens (vs 2 stamens), but they are otherwise very similar. We do not consider those differences as sufficient to distinguish another taxon. Inversodicraea nicolasii is solely known from four collections, which suggests a morphological variability that was unsuspected until now, and that remains largely undocumented.

Figures

Figure 3. Photographs illustrating a selection of species treated in this paper. A, B. Inversodicraea annithomae (A: Boupoya et al. 2444; B: Boupoya et al. 2689). C. Inversodicraea boumiensis (Boupoya et al. 1748). D, E. Inversodicraea nicolasii (D: Texier et al. 2247; E: Texier et al. 2334). F, G. Inversodicraea paulsitae (Boupoya et al. 1750). H, I. Inversodicraea tenax (H: Boupoya et al. 2432; I: Boupoya et al. 2430). Photographs: Igor Nguimbit (A), Archange Boupoya (B, C, F-I), Nicolas Texier (D, E).

Figure 4. Distribution maps of Podostemaceae in Gabon. A. Inversodicraea annithomae (grey circles), I. boumiensis (red diamonds). B. Inversodicraea nicolasii (red diamonds), I. paulsitae (grey circles), I. tenax (orange triangles). C. Inversodicraea thollonii (red diamonds), Ledermanniella bifurcata (grey circles). D. Ledermanniella aloides (grey circles), L. schlechteri (red diamonds).

Figure 5. Drawing of Inversodicraea nicolasii. A. Sterile shoot tip with young leaves and stem scales (scale bar: 0.5 mm). B. Fertile shoot before anthesis (scale bar: 5 mm). C. Capsule, one valve removed (scale bar: 1 mm). D. Flower at anthesis (scale bar: 2 mm), ovary with two stigmas dropped. E. Cross-section of the ovary (scale bar: 0.5 mm). F. Detail of the ovary (scale bar: 1 mm). G. Fertile lateral shoot and portion of the main stem (scale bar: 1 cm). A, E, F: Texier et al. 2247; B: Nguimbit et al. 8; C, D: Boupoya et al. 2445; G: Nguimbit et al. 7. Drawings by Anne-Helene Paradis, based on preliminary drawings by Rolf Rutishauser.