Inversodicraea annithomae (C.Cusset) Rutish. & Thiv (Thiv et al. 2009: 72)

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 annithomae (C.Cusset) Rutish. & Thiv (Thiv et al. 2009: 72)

Figs 3A, B , 4A

Ledermanniella annithomae C.Cusset ( Cusset 1983: 377, plate 6)

Type.

GABON • Booué; 29 Jul. 1966; [0°05 ’24” S, 11°55 ’59” E]; 165 m; fl., fr.; N. Hallé & A. Le Thomas 206; holotype: P [P00179254] .

Distribution.

Gabon, Republic of the Congo. Before 2017, this species was only known from two collections: the type collected in 1966 at Booué in the Ogooué river in Gabon, and a collection made by Sita at the Mandoro rapids in the Republic of the Congo, in a tributary of the Kouilou river. Between 2018 and 2020, six collections were made, and its presence was confirmed at Booué. It was also discovered at another site in the Ogooué, the Poubara falls, and it is therefore probably present elsewhere on the Ogooué river, though it has not yet been collected at several other visited sites along the river. One collection is also known from the Okano river, a tributary of the Ogooué. The collection by Sita was determined by Colette Cusset in 1998, but since the P (P00179255) specimen shows stems branched multiple times, it was mentioned as doubtful in the synoptic revision of the genus ( Cheek et al. 2017), though not providing a different determination since they did not observe the specimen. Cheek et al. (2017) also described Inversodicraea tchoutoi Cheek, to which they associate the collection Letouzey 10299, initially determined as I. annithomae by Cusset. Cheek et al. (2017) hence consider I. annithomae as a species endemic to the Booué rapids. Since recently collected material revealed morphological variability in I. annithomae (see Notes), we chose to stick with Cusset’s determination of the Sita collection, and to consider this species as present in the Republic of the Congo. Moreover, since this species was found at Poubara (only ca 150 km away from Sita’s collection site), it is also probably present in the Ogooué river upstream of Poubara, where rapids are present only ca 100 km away from the Sita collection site.

Habitat and ecology.

Rapids and falls in rivers from ca 90 to 410 m wide, 160-400 m in elevation. It appears to be quite rare at the sites where it has been encountered. Flowers and fruits were collected in July and August, and fruits in September. It is mostly found in micro-habitats submitted to strong currents, but can also be found in slower-running water.

Notes.

Recent collections revealed a strong morphological variability: the collection Boupoya et al. 2698 shows cable-like horizontal stems more than 5 mm thick and up to 30 cm long, sparsely covered by scale-leaves, and bearing axillary, short flowering shoots abundantly covered by scale-leaves, while the collection Boupoya et al. 2684 shows upright flowering shoots of up to 2 cm long, with stems up to 1.5 mm in diameter, abundantly covered by scale-leaves, and attached to a ribbon-like root. Intermediate forms were also collected (Boupoya et al. 2672 and 2682), showing typical features of I. annithomae , but with upright to horizontal shoots up to 5 cm long and 3 mm thick, still covered by scale-leaves on ca 50-60% of their surface. The three forms (small and upright, medium and upright to horizontal, large and horizontal) may be developmental stages as well as environmental modifications, but more precise field observations and habitat characterization is needed to explain this morphological variability. The morphological variability of I. annithomae was previously indirectly postulated by Cusset, who determined the sterile specimen Letouzey 10299 as I. annithomae , probably considering that the absence of long, flexible flowering stems (as for the typical form of the species) was the result of a juvenile stage ( Cheek et al. 2017).

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).