A new cloud forest tree Lychnodiscus bali (Sapindaceae), Critically Endangered from the Bali-Ngemba Forest Reserve, NW Region, Cameroon

We describe and illustrate Lychnodiscus bali Cheek (Sapindaceae), a new species to science, from the Bali Ngemba Forest Reserve of NW Region Cameroon, the last major remnant of cloud forest in the Bamenda Highlands of Cameroon, recently evidenced as a Tropical Important Plant Area (TIPA or IPA). Confined on current evidence to upper submontane forest, the new species is threatened by expanding habitat clearance for farms and is assessed as Critically Endangered. A small tree, attaining 3 – 4 m height, it is the first new species to be added to this Guineo-Congolian tree genus in 50 years, the third recorded from Cameroon and takes the number of species in the genus to eight. It has the highest known altitudinal range (1700 – 1950 m alt.) of any species of the genus. We discuss its discovery in the context of other recently discovered and highly threatened or even extinct plant species in the Cameroon Highlands, and the importance of their conservation. The new species was previously identified as Lychnodiscus grandifolius Radlk., but differs in the shorter length of the distal leaflets (12 – 18 cm vs 22 – 39 cm long); in the abaxial leaf surface lacking glands (vs glands flat and conspicuous); in being sparsely hairy all over (vs glabrous except the main veins) and in its larger flowers, 8 – 11 mm long at anthesis (vs 5 – 7 mm long). We present an identification key of the species of Lychnodiscus and discuss their classification in the context of recent molecular phylogenetic and phylogenomic studies. The authors contend that Lychnodiscus Radlk., previously placed in Cupanieae by Radlkofer, should now be placed in the reconstituted Nephelieae in the revised 2021 intrafamilial classification of Buerki et al., probably close to the genera Aporrhiza Radlk. and Laccodiscus Radlk. However, until the genus is included in molecular studies this cannot be confirmed and a sister relationship remains speculative.