Tristicha trifaria (Bory ex Willd.) Spreng. (Sprengel 1824: 22)

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

Tristicha trifaria (Bory ex Willd.) Spreng. (Sprengel 1824: 22)

Fig. 7D

Type.

MAURITIUS • fl., fr.; Bory de Saint Vincent s.n.; holotype: P [P00632465]; isotype: B [B - W 00085 -01 0] .

Distribution.

Tropical Africa, South and Central America, Madagascar, and islands of the western Indian Ocean. Before 2018, this species was known from Gabon from a single collection made by Frans Breteler in the Okano river (in 1978). Since 2018, 46 collections have been made in Gabon, in most of the rivers that were explored by authors and colleagues, to the notable exception of the Ivindo river. Tristicha trifaria is now considered one of the most common Podostemaceae species in Gabon.

Habitat and ecology.

Falls and rapids in rivers from ca 20 to 600 m wide, 15-575 m in elevation (in Gabon). This species is widely distributed, and appears abundant and ecologically ubiquitous. It has been found in the largest rivers ( Ogooué) as well as in small, forested rivers (Bibaka, Méba, etc.). Apparently, it can form small, monospecific patches, but was often found in association with other Podostemaceae species. In Gabon, flowers and fruits were collected in July, August, and September.

Notes.

Tristicha trifaria is here considered as a single, very polymorphic and ubiquitous species, as suggested by Cook and Rutishauser (2007). Nevertheless, several subspecies were described, but their validity remains uncertain, and more phylogenetic studies are needed to untangle this complex ( Kita and Kato 2004; Koi et al. 2015). A complete synonymy is provided in Cusset and Cusset (1988a) and is not reproduced here. The discovery of the commonness of T. trifaria in Gabon is less surprising than the fact that it was not discovered earlier. This is probably the result of an historic sampling bias towards the larger Podostemaceae species, even during the few inventories targeted on this family. As an example, Nicolas Hallé and Annick Le Thomas collected six species at Booué in 1966, but not T. trifaria , which the authors and colleagues have collected five times at this site in 2019 and 2021.

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).