Inversodicraea thollonii (Baill.) Cheek

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 141

19. Inversodicraea thollonii (Baill.) Cheek

Inversodicraea thollonii (Baill.) Cheek in Cheek & Haba (2016a) 2. — Ledermanniella thollonii (Baill.) C. Cusset (1983) 388; (1984) f. 13. — Podostemum thollonii Baill. (1890) 877. — Type: Thollon 825 (holotype P P00179381 image; isotype BM, P00179380 image), Gabon, Ogooué, Rapides de Lopé, fl., fr., 1887.

Etymology. Named for François-Romain Thollon (1855–1896), an early French botanist in Gabon and Congo and collector of the type specimen

Distribution — Gabon, Ogooué River.

Habitat & Ecology — Rapids in the Ogooué River; c. 200 m altitude.

Conservation — We here assess I. thollonii as Critically Endangered since the natural fluctuations of water flow in the Ogooué River, wherein occur its two sites (one location since facing the same threat), are being affected by the opening in 2013 of the Grand Poubara dam built by China’s Sinohydro http://www.gauff.net/en/news/articles/article/beginn-desaufstaus-im-wasserkraftwerk-grand-poubara.html. Among other hydroelectric projects under construction in the area one is also on the major tributary Ogooué River upstream of our species at the Chutes de l’Impératrice (https://www.afdb.org/ fileadmin/uploads/afdb/Documents/Environmental-and-Social- Assessments/CDI%20R%C3%A9sum%C3%A9%20PGES%20 coder%20french% 2025-05-12. pdf). The two sites and single location for this species equate to an area of occupancy of 2 km 2 using the standard IUCN cell size for riverine plants. This gives an assessment of CR B2 ab(iii). Currently the species is not listed on www.iucnredlist.org.

Additional specimen. Gabon, Booué, lit de L’Ogooué, fr., 29 July 1966 ,

N. Hallé & A. Le Thomas 202b (P00179379 image).

Notes — Inversodicraea thollonii is still only known from rapids in the Ogooué River of Gabon at two sites which are so close together (a maximum of 36 km apart, on the same river) that it can be argued that they should be treated as one location since they both face the same threat. The most recent record is over 40 years old. This species is linked with I. kamerunensis and I. adamesii by the slender, loosely branched stems, sparsely covered with irregularly 1–3-lobed membranous scale-leaves. These species are also unusual in the elongate spathellum c. 4–7 times as long as broad, and by the androphore exceeding the ovary. Within this group it is distinguished by the soft, entire, nail-like scale-leaves on the middle of the stem, and, but more elongate and curved, at the stem apex.