Inversodicraea congolana Hauman

Tchouto, P. & Burgt, X. van der, 2017, A synoptic revision of Inversodicraea (Podostemaceae), Blumea 62 (2), pp. 125-156 : 136

6. Inversodicraea congolana Hauman

Inversodicraea congolana Hauman (1944) 179; (1948) 244. — Ledermanniella congolana (Hauman) C. Cusset (1974) 273; (1983) 374. — Type: Vanderijst 21682 (BR n.v.), Congo-Kinshasa ( DRC), Chutes de Luilu, Thielen St. Jacques, fr.

Etymology. Named for the Congo (now DRC) to which this species is endemic.

Distribution — DRC.

Habitat & Ecology — Rapids; 300–775 m altitude.

Conservation — Inversodicraea congolana is not listed in www.iucnredlist.org. It was only known from two falls. The first was at the set of falls on the Tshopo where a hydroelectric dam has been installed since the species was collected. Here the Tshopo joins the Congo near Kisangani, DRC’s third largest city. It is notable that there are no records of Inversodicraea from the vastly more extensive Wagenya (Boyama) Falls, also at Kisangani, but on the Congo River itself. These falls extend upriver for about 100 km in a series of step falls none more than 5 m vertically. This absence is probably due to the high silt levels of the water of the Congo River, which viewed on Google Earth are brown, unlike the clear water of the smaller Tshopo River.

The second location for the species was also recorded in the grasslands of the Kasai at Thielen St Jacques, now Mwene- Ditu, specifically at Chutes de Luilu on a braided river where no obvious threats are visible on Google Earth. Accordingly we calculate the area of occupancy as 2 km 2. Construction of the dam at the Tshopo Falls is thought to have impacted on the species, principally by reducing the total volume of water flowing over the falls (much has now been diverted around the falls via a penstock) and also by disrupting the natural seasonal water flow regime at the falls, constituting threats. According to Léonard (1993), citing Nyakabwa (1982), I. congolana , which he discovered and surveyed at the site in 1947, no longer occurs there and is locally extinct. Therefore we assess the species as Endangered, EN B2 ab(iii). A survey for the species at the Tshopo site is still advisable to determine whether or not some last few plants might still survive there.

Additional specimen. DRC, Kisangani, Chutes de Tshopo , fr., July 1947 ,

Léonard 1346 (BR n.v.).

Note — This is the sole member of the genus known from DRC apart from I. tenax towards the southern border. Inversodicraea congolana occurred at two isolated locations: 1) in the forest belt almost within the city limits of Kisangani; and 2) in the Kasai grasslands towards the border with Angola. These two locations are so far apart, and in such different vegetation types that both specimens deserve comparison to confirm that they are indeed conspecific. Neither specimen has been examined in this study since BR specimens were not accessible in 2016/2017 owing to a digitisation programme. Inversodicraea congolana is distinctive for its pair of ovary apical wings, derived from the two median longitudinal ovary ribs. The same character occurs in I. warmingiana of Angola (but on all six longitudinal ribs) and in I. feika of Sierra Leone, I. eladii and I. ebo of Cameroon. Inversodicraea congolana is also unusual in having dorsal protuberances on its leaflet. It is unique in the genus in combining this character with winged ovaries.