Inversodicraea annithomae (C.Cusset) Rutish. & Thiv

10. Inversodicraea annithomae (C.Cusset) Rutish. & Thiv View in CoL

Inversodicraea annithomae (C.Cusset) Rutish.& Thiv View in CoL ( Thiv et al.(2009) 72). — Ledermanniella annithomae C. Cusset (1983) View in CoL 377, f. 6; (1987) 76. — Type: N. Hallé & A. Le Thomas 206 ( holotype P00179254 image), Gabon, Booué, lit de l’Ogooué, fl., 29 July 1966.

Etymology. Named for Annique Le Thomas co-collector of the type specimen and a noted specialist of Annonaceae and a palynologist at P.

Distribution — Gabon. Only known from the type specimen at Booué.

Habitat & Ecology — River rapids of the Ogooué R. ‘4 es- pèces en mélange sur rochers’ ( type, N. Hallé & A. Le Thomas 206) with Ledermanniella nicolasii C.Cusset ( 205), L. pusilla (Warm.) C.Cusset ( 202), Macropodiella hallaei C.Cusset ( 203), M. heteromorpha (Baill.) C.Cusset ( 201, 204), I. annithomae , and I. thollonii ( 202bis) at c. 200 m altitude.

Conservation — Inversodicraea annithomae (as Ledermanniella ) was assessed in www.iucnredlist.org as Endangered (EN B2 ab(iii) in 2007 ( Ghogue 2010a), and also by Cheek (in Onana & Cheek 2011), citing only two known locations, one in Cameroon and one (the type) location in Gabon. In this paper, the population in Cameroon is shown to be a misidentification for I. tchoutoi (see above, and under that species). This leaves only a single location, the type, for I. annithomae . The area of occupancy is therefore estimated as 1 km 2. Given threats from hydroelectric dams on the Ogooué River, of which the Grand Poubara, upstream, that opened in 2013, is the first, the future for this species is bleak.

Since such dams moderate the natural seasonal fluctuation of water levels downstream, they can deprive Podostemaceae of the drop in water level needed to expose plants and so allow flowering and seed production, and thus regeneration. Accordingly, we here reassess the threat to this species as CR B2 ab(iii), that is Critically Endangered.

Notes — The sterile paratype cited in the protologue, Letouzey 10299, ‘Chutes du Ntem ou de Memve’ele, près Nyabessan, 60 km E Campo ( st. avr .)’ is a different taxon to that of the type, and is described, with several new, fertile specimens from the same location, as I. tchoutoi in this paper. Inversodicraea annithomae itself, appears to be confined to Gabon and is only known from the type collection. References to I. annithomae from the Ntem River of Cameroon, and its appearance in phylogenetic analyses (e.g., Thiv et al. 2009, Schenk et al. 2015) probably refer to I. tchoutoi . The differences between the taxa are given in a table in the account for the last species.

The Paris website lists under this species Sita 5856 (P00179255 image), from Congo, Chaillu, Rapide de Mandoro, 3 ponts, 6 June 1985, identified by C.Cusset in 1998. Since the specimen shown is highly branched, we consider this determination to be unlikely, but image resolution was insufficient to provide an alternative determination .

Inversodicraea annithomae is one of the most distinctive members of the genus. Together with I. paulsitae it is unique in having long ( 5–25 cm), flexible, unbranched floating stems, with regular internodes, each node with a short, densely leaflet-clad flowering stem opposite to a long, dichotomously branched leaf. While the last species has deeply 3-lobed scale-leaves, I. annithomae has almost entire scale-leaves.

In fact, at the type location near Booué, six species of Podostemaceae were collected by N. Hallé & A. Le Thomas when collecting the type specimen, and probably there are seven since Tristicha trifaria is very likely to be present, being ubiquitous.