Ledermanniella pygmaea (Pellegr.) C.Cusset (Cusset 1984: 266)

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

Ledermanniella pygmaea (Pellegr.) C.Cusset (Cusset 1984: 266)

Figs 6H , 7B

Sphaerothylax pygmaea Pellegr. ( Pellegrin 1927a: 268)

Type.

GABON • Samba waterfall in the Ngounié river, near Sindara ["Chutes de Samba, Sindara, dans la Ngounyé”]; 30 Jun. 1917; [1°02 ’23” S, 10°41 ’44” E]; 35 m; fl., fr.; Le Testu 2202; holotype: P [P00179351]; isotype: BM [BM000910392] .

Distribution.

Endemic to the Ngounié and Louétsi rivers, in Gabon. Before 2017, this species was solely known from the type collection made at Samba (or Tsamba) falls on the Ngounié river, west of Sindara (Le Testu 2202, gathered in 1917). It was found again one century later, in 2018, at three different sites on the Louétsi river, a tributary of the Ngounié, and collected 10 times in 2018 and 2021. Surprisingly, recent inventory at the type locality did not allow to collect this species again, despite the apparent lack of disturbance and immediate threat to this site.

Habitat and ecology.

Falls in rivers from ca 35 to 170 m wide, 35-450 m in elevation. It is very localized when encountered, but forming dense, apparently monospecific mats. Flowers and fruits were collected in June and August. In the Louétsi river, it has been found in close vicinity with L. aloides and L. pusilla . This species seems restricted to falls, in fast flowing water, as it was not collected in smaller rapids areas in the Louétsi river.

Notes.

The presence of both stemless shoots and developed stem up to 8 mm long was already mentioned by Cusset (1984), and is confirmed by the recent observations. This species is recognizable by the combination of ribbon-like root, pollen in dyads, a single stamen, leaves arranged all around the stem (not distichous), that are linear, entire to 3-4 times forked. When a developed stem is present, the leaves at base are usually shorter, sometimes damaged, which can give the impression of stem-scales. Nevertheless, there is a continuum in length and shape between basal and apical leaves, which suggests no true stem-scales (as typical for Inversodicraea ) are present in this species.

Figures

Figure 6. Photographs illustrating a selection of species treated in this paper. A, B. Inversodicraea thollonii (A: Boupoya et al. 1948; B: Boupoya et al. 1943). C. Ledermanniella aloides (Boupoya et al. 1749). D, E. Ledermanniella bifurcata (D: Boupoya et al. 1954; E: Boupoya et al. 1958). F, G. Ledermanniella pusilla (F: Boupoya et al. 1733; G: Boupoya et al. 1735). H. Ledermanniella pygmaea (H: Boupoya et al. 1764). Photographs: Archange Boupoya.

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).