Englerophytum rwandense (Troupin) Eb.Fisch., 2024

Fischer, Eberhard, Nsanzurwimo, Aimable, Dumbo, Bonny, Richter, Ronny & Weghe, Jean Pierre Vande, 2024, An updated checklist of vascular plants (lycophytes, ferns, gymnosperms, angiosperms) from Nyungwe National Park (incl. Cyamudongo Forest), Rwanda, Phytotaxa 673 (1), pp. 1-113 : 106

Englerophytum rwandense (Troupin) Eb.Fisch. , comb. nov.

Basionym: — Chrysophyllum rwandense Troupin (1982: 463)

Homotypic synonyms:— Zeyherella rwandensis (Troupin) Liben (1989: 258) ; Afrosersalisia rwandensis (Troupin) Liben (1991: 355)

Type: — RWANDA. Western Province, Nyungwe National Park, Wisumo, commune Gisovu , centre forestier, 2300 m, 20 February 1980, D. Bridson 432 (holotype BR [ BR0000008962485 ]; isotype K, NHR)

Notes:— Borg et al. (2019) conducted a molecular analysis of two genera of Sapotaceae , and showed that Zeyherella ( Engler 1904: 46) Pierre ex Aubréville & Pellegrin (1958: 37) is nested in Englerophytum Krause (1914: 343) . Thus, the plant described by Troupin (1982) has to be placed in Englerophytum . The necessary combination is made above. Englerophytum rwandense was previously placed in Zeyherella and Afrosersalisia A.Chev. ( Liben 1989, 1991).

Englerophytum rwandense was described from the northern part of Nyungwe National Park. It is only known from few localities in the northern and western Nyungwe (Wisumo, Kibazi, Rangiro), eastern D. R. Congo, and western Burundi ( Ntore et al. 2018).

7. Discussion

Plumptre et al. (2002) list 242 species of vascular plants in the studied 13 plots of Nyungwe , among them 24 endemics. Plumptre et al. (2007) give an overview of other forests in the Albertine Rift and their diversity ( Table 7). The Bwindi Impenetrable National Park in South-Western Uganda has 1405 species of vascular plants, among them 74 Albertine Rift endemics (5.26%). The Kahuzi-Biéga National Park in the Eastern Democratic Republic of the Congo has 1171 species of vascular plants, among them 145 Albertine Rift endemics ( Fischer 1996). The majority of the Kahuzi-Biéga National Park is covered by lowland and mid-altitude rainforest between 850 m and 1100 m a.s.l. The highest peaks Mt. Kahuzi and Mt. Biéga reach up to 2900 m and 3350 m a.s.l. respectively. For Nyungwe the numbers given by Plumptre et al. (2007) are now considerably higher due to continuous exploration of the flora. They mention 1105 species of vascular plants and 137 Albertine Rift endemics. Today we have recorded 1453 species of vascular plants with 258 Albertine Rift endemics. Thus, the percentage of endemics in Nyungwe National Park (17.55%) is quite high. In Rwanda, a total of 346 species of vascular plants are endemic or near endemic (Fischer unpubl.). Thus, the total percentage of endemics for the country is 11.5%.

The adjacent country, Burundi, has been studied recently by Ntore et al. (2022) and a checklist of the vascular plants is in preparation. In Burundi, 3860 species have been recorded of which 135 species have been recognized as endemics or near endemics ( Ntore et al. 2018). This is 3.5% of the total flora. Recently, seven new species have been added ( Fischer et al. 2016, 2021a, b, 2023) raising the percentage of endemics to 3.7%. For Kibira National Park, the prolongation of Nyungwe , nine endemic or near and endemic ferns, and 66 endemic or near-endemic flowering plants have been recorded, which is significantly less than in Nyungwe National Park.

If we compare Nyungwe National Park with other National Parks in East Africa there are considerable differences. The Aberdare Forest in Kenya is a significant regional centre of plant diversity. With a total of 1260 taxa recorded, it represents 17.9% of the total 7004 vascular plants in Kenya ( Kipkoech et al. 2020). The taxa-rich families in the Aberdare ( Asteraceae , Fabaceae , and Poaceae ) were consistent with studies done in other regions in Kenya. In Aberdare, 141 species of Asteraceae , 103 species of Poaceae , 83 species of Fabaceae , and 34 species of Orchidaceae were recorded ( Kipkoech et al. 2020). The most species-rich gernera are Cyperus (20), Helichrysum (19), Senecio and Asplenium (17), and Crotalaria and Solanum (15). Endemic taxa in the Central Highlands of Kenya, comprising the Aberdare and Mt. Kenya Forests, represent 3.1% of the total 577 endemics in Kenya and 0.8% of the total flora. The transboundary Elgon National Park, situated in Uganda and Kenya, has 1589 species of vascular plants ( Cheptoo Rono et al. 2023). The most species-rich families are Asteraceae (191), Fabaceae (168), and Orchidaceae (114). The most speciose genera are Cyperus (31), Asplenium (29), Crotalaria (27), Habenaria (25), Helichrysum (24), and Coleus (21) ( Cheptoo Rono et al. 2023).

There are several features that make Nyungwe National Park unique, i.e., the high number of orchids that comprise the most speciose family. Also, the percentage of endemic or near endemic vascular plants is higher than in any other area inside or outside the Albertine Rift ( Table 7).