Macropodiella heteromorpha (Baill.) C.Cusset (Cusset 1978: 298)

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 heteromorpha (Baill.) C.Cusset (Cusset 1978: 298)

Fig. 7B

Sphaerothylax heteromorpha Baill. ( Baillon 1890: 876) - Type: same as for Macropodiella heteromorpha .

Macropodiella mildbraedii Engl. ( Engler 1926: 466, plate 4) - Type: CAMEROON • Nyong river, south of Yaoundé ["Auf Felsblöcken im Nyong, südlich von Jaunde"]; Jan. 1914; [3°30 ’30” N, 11°29 ’33” E]; 640 m; fl.; Mildbraed 7749; holotype: B [B 10 0294990].

Type.

GABON • Rapids in the Ogooue river at Lopé ["Rapides de Lopé”]; Feb. 1887; [0°05 ’38” S, 11°35 ’24” E]; 110 m; fl., fr.; Thollon 729; holotype: P [P00179126]; isotypes: P [P00179127, P00179128] .

Distribution.

Ivory Coast, Cameroon, Gabon. This species was originally described based on material collected by Thollon in 1885 and 1887 in the Ogooué river, at the Lopé rapids. It is also known from the Ivindo river (Florence 527) and the Ogooué rapids at Booué (N. Hallé 201 and N. Hallé 204). In Cameroon, it is known from the Nyong (at Mbalmayo and south of Makak) and Ntem rivers ( Mve’ele and Campo falls). A single collection is known from Ivory Coast: Guillaumet 1569 on the Cavally river. A collection from Courtet, without collection number, is available in Paris, but its locality data are considered as very doubtful (see Notes for M. hallaei ). Since 2019, it was collected three times by the authors and colleagues, in the Lenké river (a small tributary of the Ogooué near Booué) and in the Ivindo river (at the Touné falls near its confluence with the Ogooué).

Habitat and ecology.

Falls and rapids in rivers from ca 40 to 600 m wide, 40-640 m in elevation. Unlike M. hallaei , this species is widely distributed, but appears to be rare when encountered. It is apparently restricted to micro-habitats submitted to fast-flowing water. In the Lenké river, it has been found mixed with I. thollonii and L. aloides . In Gabon, flowers and fruits were collected in January, February, and July, and in Cameroon in January, February, July, and December. In Gabon, old fruits were observed in early September.

Notes.

Surprisingly, recent inventories carried out at the Ogooué rapids near Booué in 2019, 2020, and 2021 did not allow to rediscover this species at this site, though having been collected there in 1966 by Nicolas Hallé and Annick Le Thomas, and then noted as being abundantly present. Nevertheless, recent inventories revealed its presence in the Lenké river only 8 km northwest of Booué, and the Touné falls of the Ivindo, 30 km east of Booué. We cannot exclude the possibility of a natural replacement of this species by M. hallaei over time, which shares the same micro-habitats and was recently noted as very abundant at Booué. Such mechanisms are only postulated and would need further studies to be confirmed and understood. Even though M. heteromorpha was not recently collected at Booué, its absence from this large area of rapids (ca 550 × 900 m), difficult to access in their entirety, is not certain. This site does not seem to have suffered from any particular human-induced impact, but it is yet unknown whether past stochastic events (such as exceptional natural disturbances of the seasonal variations of water levels) may have favoured one species over another. It is also possible that in such a dynamic environment, natural species replacement may occur without any human-induced impact or natural stochastic extreme climatic events. Long-term surveys of selected areas should be designed to explore these questions, and the Booué rapids seem a good candidate, being located near the city and comprising eight different species.

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).