Keetia nodulosa sp. nov. (Rubiaceae - Vanguerieae) of West-Central Africa: bacterial leaf nodulation discovered in a fourth genus and tribe of Rubiaceae

Abstract

Keetia nodulosa Cheek, a cloud forest climber nearly endemic to Cameroon, with a single record from Nigeria, is described and illustrated. It is remarkable as the first known species to be recorded with bacterial leaf nodules (BLN) in the genus Keetia, and also, in the tribe Vanguerieae. Other genera in Rubiaceae with BLN are Psychotria (Psychotrieae-Rubioideae), Sericanthe (Coffeeae) and Pavetta (Pavetteae), both Ixoroideae/Dialypetalanthoideae. The BLN in Keetia (Vanguerieae) are illustrated for the first time here. The characteristics and significance of bacterial leaf nodulation in Keetia nodulosa are discussed in the context of rapidly growing knowledge on the subject in flowering plants. Keetia nodulosa is provisionally assessed using the 2012 IUCN standard as Endangered (EN B2ab(iii)). The importance of its conservation, and options for achieving this are discussed in the context of recent extinctions of other plant species in Cameroon. This discovery of a new cloud forest species is discussed in relation to other cloud forest plant species described in the last twenty years which are also distributed over the highlands of the western half of Cameroon.

Afrothismia ugandensissp. nov. (Afrothismiaceae), Critically Endangered and endemic to Budongo Central Forest Reserve, Uganda

“…The case of Afrothismia ugandensis , formerly included in the apparently greatly disjunct Cameroon/Gabon species A. winkleri (albeit recognised as varietally different), suggests that it might repay effort to reexamine other such cases of apparently far disjunct species with this range. A recent re-assessment of another such disjunct species (western Uganda and Cameroon) species, Keetia purseglovei Bridson (Rubiaceae), showed that the Cameroon material was a separate species from the Ugandan (Cheek & Onana 2024). A further example of an apparently widespread and Cameroon/Ugandan disjunct taxon, Dovyalis spinosissima Gilg (Salicaceae) also led to the recognition of distinct species in both countries after further taxonomic study (Cheek & Ngolan 2007).…”

Keetia gordoniisp. nov. (Rubiaceae - Vanguerieae) a new species of threatened forest liana from the littoral forest of Gabon

“…The format of the description follows those in other papers describing new species of Keetia , e.g. Cheek & Bridson (2019), Cheek & Onana (2024). Terminology follows Beentje & Cheek (2013).…”

“…(2017), Cheek et al . (2018a), Cheek & Bridson (2019) and Cheek & Onana (2024), and several other taxa that fit no other species, (e.g. Cheek et al 2004; 2011)) remain to be described.…”

“…One of these species was later taken up and published by Jongkind (2002) as Keetia bridsoniae Jongkind. In the same paper, Jongkind discovered and published Keetia obovata Jongkind based on material not seen by Bridson. Based mainly on new material, additional new species of Keetia have been published by Bridson & Robbrecht (1993), Bridson (1994), Cheek (2006), Lachenaud et al (2017), Cheek et al (2018a), Cheek & Bridson (2019) and Cheek & Onana (2024), and several other taxa that fit no other species, (e.g. Cheek et al 2004;2011)) remain to be described.…”

“…by Bridson (1985Bridson ( , 1986. Restricted to sub-Saharan continental Africa (absent from Madagascar and the Mascarene Islands), and extending from Senegal and Guinea in West Africa (Gosline et al 2023a;2023b) to Sudan in the North and East (Darbyshire et al 2015) also Ethiopia, and S. Africa in the South (Bridson 1986), this genus of about 41 accepted species (Cheek & Onana 2024) are distinguished from similar Canthioid genera in west Africa by their pyrenes with a fully or partly-defined lid-like area around a central crest and endosperm with tanniniferous areas (Bridson 1986). Keetia species are mainly climbers of forest (rarely shrubs of wooded grassland or small trees).…”