Macropodiella hallaei C.Cusset (Cusset 1978: 300)

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

Macropodiella hallaei C.Cusset (Cusset 1978: 300)

Figs 7C , 8F, G

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 203; holotype: P [P00179111]; isotypes: BR [BR0000009211575], P [P00179112, P00179113, P00179114], WAG [WAG0194843] .

Distribution.

Endemic to the Ogooué and Ivindo rivers, in Gabon. Before 2018, this species was solely known from three collections: Hallé 203 (the type collection) from the Ogooué rapids at Booué, Thollon 728 from the Ogooué rapids at Lopé, and Courtet s.n., supposedly from the Chari or Congo rapids. However, collections attributed to Henri Courtet are highly suspicious with respect to their geographical origin. According to Cusset (1978, see Notes under Macropodiella heteromorpha ), Courtet did collect a few specimens during Auguste Chevalier’s 1902-1904 expedition in the “Haut-Chari” region. But it is unsure if Courtet’s collections from the d’Alleizette Herbarium were collected by him or are Chevalier’s collections that were wrongly attributed to Courtet by Charles d’Alleizette. In addition, all collections from Central Africa labelled as Karmann or d’Alleizette are suspected to be nothing more than fragments of other collections made in Central Africa mainly by Georges Le Testu or Théophile Klaine, as it has been proven by examination of the material from other plant families made by Olivier Lachenaud and the authors of this paper. In the case of the Courtet collection of M. hallaei , we can thus not be sure it was indeed collected in the Chari river by Courtet (which would represent a significant and quite surprising extension of the distribution range of the species) or if it is a collection initially collected by Chevalier, or even if it is a fragment of Thollon 728. Until more research is done on the d’Alleizette Herbarium, we prefer to consider the latter as the most probable explanation. Between 2018 and 2021, 22 collections of this species were gathered by the authors and colleagues, mostly at and around the type locality near Booué, in the Ogooué river. In 2018 and 2019, M. hallaei was discovered at two different sites on the Ivindo river: at the Touné falls (located 3.5 km away from the confluence with the Ogooué) and the Kongou falls. Inventories carried out upstream in the Ogooué river, especially around Lastoursville, Poubara, and at the border with the Republic of the Congo, did not yield this species. Macropodiella hallaei is the most commonly found Macropodiella species in Gabon.

Habitat and ecology.

Falls and rapids in rivers from ca 390 to 750 m wide, 110-465 m in elevation. This species appears to be very abundant when encountered. It appears to be found mostly in the middle of rivers rather than on the rocky banks, and in fast-flowing water, where it forms dense monospecific mats. At the Booué rapids, it has also been found mixed with I. thollonii , L. pusilla , and Tristicha trifaria . Flowers and fruits were collected in February, July, and August. Old fruits were observed in early September.

Notes.

The recently collected material is very consistent with Cusset’s original description of M. hallaei ( Cusset 1978). Minor morphological variations can nonetheless be reported. Most individuals show elongated stems, but a few stemless fertile shoots were also observed. In addition, a few stigmas are clearly papillose, among most of them being globose (sometimes bilobed) as mentioned by Cusset. Most flowers bear three stamens, but can occasionally have two, or rarely four.

Figures

Figure 7. Distribution maps of Podostemaceae in Gabon. A. Ledermanniella pusilla (red diamonds), L. tenuifolia (grey circle). B. Ledermanniella pygmaea (grey circles), Macropodiella heteromorpha (red diamonds). C. Macropodiella hallaei (grey circles), Saxicolella nana (red diamonds). D. Tristicha trifaria (grey circles).

Figure 8. Photographs illustrating a selection of species treated in this paper. A, B, C. Ledermanniella schlechteri (A: Texier et al. 2335; B: Texier et al. 2274; C: Texier et al. 2250). D, E. Ledermanniella tenuifolia (D: Boupoya et al. 2417; E: Boupoya et al. 2426). F, G. Macropodiella hallaei (Texier et al. 2249). H, I. Saxicolella nana (Boupoya et al. 1952). Photographs: Nicolas Texier (A-C, F, G), Archange Boupoya (D, E, H, I).