Biology subjects

Sonke, B.

Publications and source records attributed to Sonke, B..

5 recordsLinked to original sources

bioRxiv2025

Notes on the endemic and near endemic threatened rainforest plant species of Banyang Mbo Wildlife Sanctuary, SW Region, Cameroon, and Tricalysia banyangmbo sp nov. (Rubiaceae-Coffeeae) a new coffee relative.

Species new to science discovered from the Banyang Mbo Wildlife Sanctuary (BMWS) of SW Region Cameroon are reviewed and summarised, as are species listed as threatened which have been recorded, both from A. lowland evergreen forest and B. from cloud (submontane) forest. In total five globally Critically Endangered, 17 Endangered and 21 Vulnerable plant species are listed for BMWS. We describe an additional narrow endemic of BMWF, Tricalysia banyangmbo sp. nov. (Sect. Tricalysia Rubiaceae-Coffeeae), similar in the subulate calyx lobes exceeding the calyx tube, and in the stems being densely patent shortly hairy to T. sylvae Robbr. of Littoral, South Region, Cameroon and Gabon. The new species differs in having stipules in which the awn is shorter than the blade (vs vice versa), the leaf bases are rounded (vs cordate), the blades lack domatia (vs present) and the flowers are 4([ndash] 5)-merous (vs 5 &[ndash] 6&[prime] merous), the anthers lacking a distinct and conspicuous apical connective appendage (vs present). The new species is known from three collection sites with an estimated area of occupation of c. 4 km2 and is in an area threatened by oil palm plantations. We provisionally assess the species with the 2012 IUCN standard as Critically Endangered CR B1ab(iii) + B2ab(iii).

plant biology↗

bioRxiv2025

Sericanthe etugei and S. onanae (Coffeeae Rubiaceae) new cloud forest tree species Endangered in Southwest Cameroon & Bioko (Equatorial Guinea).

Two new species of cloudforest tree are described and illustrated from the Cross-Sanaga Interval within the Lower Guinea Domain. Sericanthe etugei Cheek from South West and Littoral Regions of Cameroon is species from the Cameroon Highlands, and Sericanthe onanae Cheek from South West Region, Cameroon, and Bioko (Equatorial Guinea). Sericanthe etugei is similar to Sericanthe leonardii (N. Halle) Robbr. of DRC (Kivu) and Rwanda, differing in the stipular awn 0.25 mm long (vs 1 - 4 mm), the adaxial leaf midrib and secondary nerves glabrous (vs hairy), the tertiary nerves conspicuously scalariform with the naked eye (vs not visible). The species is also similar to Sericanthe testui var. testui, differing in being a tree (vs liana), with stems not decorticating (vs decorticating), the calyx truncate in bud (vs closed) and in the pubescent ovary (vs glabrous). Sericanthe onanae is similar to S. mpassa Sonke & Robbr. of lowland forest in Gabon, differing from that species in that the leaves have an acumen (0.5 - )0.7 - 0.8(- 1.2) cm long vs 0.3 - 0.5 cm, secondary nerves are 7 - 10 (- 12) on each side of the midrib (vs 4 - 6 in S. mpassa), and that the stipules are 5 - 6.5( - 7) x 3 - 5(- 6) mm ( vs 2.5 mm long) and truncate (vs overtopped by an awn c. 1 mm long). It is also similar to S. jacfelicis (N. Halle) Robbr., differing in that the leaves are smaller (<15 cm long vs 16 - 20 cm long), the abaxial surface of the leaf blade has 7 - 10( -12) lateral nerves on each side of the midrib (vs 5 -7) and has a glossy surface and papery texture (vs matt, coriaceous), the petioles are hairy (vs glabrous), the stipules are 5 - 6.5( - 7) mm long, truncate, lacking an awn or arista, (vs 3 -4 mm long, with an arista 0.5 - 1 mm long). These two new species are both provisionally assessed as Endangered EN B2ab(iii) with the 2012 IUCN standard. The new species are briefly discussed in the context of other newly discovered submontane species from the Cross-Sanaga Interval. We speculate that the seeds of these species may be primate-dispersed.

plant biology↗

bioRxiv2021

Kupeantha yabassi (Coffeeae- Rubiaceae), a new Critically Endangered shrub species of the Ebo Forest area, Littoral Region, Cameroon

A new species to science of evergreen forest shrub, Kupeantha yabassi (Coffeeae - Rubiaceae), is described, illustrated, mapped, and compared morphologically with the closely similar species K. pentamera. Restricted so far to a single site in evergreen lowland forest near the Ebo Forest, Yabassi, Littoral Region, Cameroon, this species is Critically Endangered using the IUCN 2012 standard due to habitat clearance driven mainly by agriculture, adding to the growing list of threatened species resulting from anthropogenic pressure on Cameroon forests. A revised key to the six species of Kupeantha is presented. Two distinct geographical and ecological species groupings within the genus are identified and discussed. Notes are given on other narrowly endemic and threatened species in the Ebo forest area, a threatened centre of diversity important for conservation in Littoral Region.

plant biology↗

bioRxiv2020

Unravelling the phylogenomic relationships of the most diverse African palm genus Raphia (Calamoideae, Arecaceae)

Palms are conspicuous floristic elements across the tropics. In continental Africa, even though there are less than 70 documented species, they are omnipresent across the tropical landscape. The genus Raphia has 20 accepted species in Africa and one species endemic to the Neotropics. It is the most economically important genus of African palms with most of its species producing food and construction material. Raphia is divided into five sections based on inflorescence morphology. Nevertheless, the taxonomy of Raphia is problematic with no intra-generic phylogenetic study available. We present a phylogenetic study of the genus using a targeted exon capture approach sequencing of 56 individuals representing 18 out of the 21 species. Our results recovered five well supported clades within the genus. Three sections correspond to those based on inflorescence morphology. R. regalis is strongly supported as sister to all other Raphia species and is placed into a newly described section: Erectae. Overall, morphological based identifications agreed well with our phylogenetic analyses, with 12 species recovered as monophyletic based on our sampling. Species delimitation analyses recovered 17 or 23 species depending on the confidence level used. Species delimitation is especially problematic in the Raphiate and Temulentae sections. In addition, our clustering analysis using SNP data suggested that individual clusters matched geographic distribution. The Neotropical species R. taedigera is supported as a distinct species, rejecting the hypothesis of a recent introduction into South America. Our analyses support the hypothesis that the Raphia individuals from Madagascar are potentially a distinct species different from the widely distributed R. farinifera. In conclusion, our results support the infra generic classification of Raphia based on inflorescence morphology, which is shown to be phylogenetically useful. Classification and species delimitation within sections remains problematic even with our phylogenomic approach. Certain widely distributed species could potentially contain cryptic species. More in-depth studies should be undertaken using morphometrics, increased sampling and more variable markers. Our study provides a robust phylogenomic framework that enables further investigation on the biogeographic history, morphological evolution and other eco-evolutionary aspects of this charismatic, socially and economically important palm genus.

plant biology↗

bioRxiv2019

Phylogenomic data reveal how a climatic inversion and glacial refugia shape patterns of diversity in an African rain forest tree species

AO_SCPLOWBSTRACTC_SCPLOWThe worlds second largest expanse of tropical rain forest is in Central Africa and it harbours enormous species diversity. Population genetic studies have consistently revealed significant structure across central African rain forest plants, in particular a North-South genetic discontinuity close to the equator at the level of a climatic inversion. Here, we take a phylogeographic approach using 351 nuclear markers in 112 individuals across the distribution of the African rain forest tree species Annickia affinis (Annonaceae). We show for the first time that the North-South divide is the result of a single major colonisation event across the climatic inversion from an ancestral population located in Gabon. We suggest that differences in ecological niche of populations distributed either side of this inversion may have contributed to this phylogenetic discontinuity. We find evidence for inland dispersal, predominantly in northern areas, and variable demographic histories among genetic clusters, indicating that populations responded differently to past climate change. We show how newly-developed genomic tools can provide invaluable insights into our understanding of tropical rain forest evolutionary dynamics.

evolutionary biology↗