Saturday, March 6, 2021

[Botany • 2020] Three New Species of Tricalysia (Rubiaceae: Coffeeae) from Atlantic Central Africa

Tricalysia lophocarpa O.Lachenaud & Sonké 

in Lachenaud, Stévart & Sonké, 2020. 


Background and aims – The genus Tricalysia A.Rich. (Rubiaceae), regarded here in the strict sense (i.e., excluding Empogona Hook.f.), includes 77 species in tropical Africa, Madagascar and the Comoros. In the current paper, three new species from Atlantic Central Africa are described and illustrated; their conservation status is also assessed.

Material and methods – This paper is based on a study of herbarium collections from BR, BRLU, K, LBV, P, WAG and YA. Normal practices of herbarium taxonomy have been applied. The conservation status assessments follow the IUCN Red List criteria.

Results – Tricalysia lophocarpa O.Lachenaud & Sonké is endemic to Gabon and is best recognised by its fruits with 8–10 narrow longitudinal ribs. Tricalysia obovata O.Lachenaud & Sonké is endemic to Equatorial Guinea (Rio Muni) and may be recognised by its obovate leaves with rounded base, glabrous stems, and sessile flowers with included style and half-exserted anthers. Tricalysia wilksii O.Lachenaud & Sonké occurs in Gabon and southwestern Republic of Congo, and may be recognised by its glabrous stems and leaves, the latter with crypt domatia, its linear calyx teeth equalling or exceeding the tube in length, and its shortly pedicellate fruits. The three species are assessed respectively as Near-threatened (T. lophocarpa), Critically Endangered (T. obovata) and Vulnerable (T. wilksii).

Keywords: Tricalysia, Rubiaceae, Coffeeae, new species, taxonomy, Central Africa, Gabon, Equatorial Guinea, Republic of Congo

Tricalysia lophocarpa O.Lachenaud & Sonké.
 A. Fruiting stem. B. Stipule. C. Detail of the domatia. D. Inflorescence. E. Flower. F. Longitudinal section of flower. G. Fruit, side view. H. Fruit, viewed from above.
A–C, G–H from Moungazi 1545; D–F from J.J. de Wilde & de Wilde-Bakhuizen11799. 
Drawn by O. Lachenaud

Tricalysia lophocarpa O.Lachenaud & Sonké, sp. nov.

Diagnosis – Ramulis breviter pubescentibus, foliis ellipticis parvis, floribusque parvis et sessilibus T. pallenti Hiern si-milis, sed differt fructibus longitudinaliter 8–10-costatis (nec laevibus), calyci lobis 0.5–1 mm longis (nec 0.1–0.5 mm), stylo glabro (nec pubescente), foliisque domatiis cryptiformibus (nec foveolatis) munitis et subtus in sicco minute granulosis (nec laevibus).

Etymology – The name lophocarpa refers to the ribbed fruits, the most diagnostic character of the species.

Tricalysia obovata O.Lachenaud & Sonké, sp. nov.

Diagnosis – Foliis obovatis basi rotundatis et ut caulibus glaberrimis, floribusque parvis et sessilibus T. amplexicauli Robbr. et T. pedunculosae (N.Hallé) Robbr. var. walkerianae(N.Hallé) Robbr. similis, sed ab ambabus conspicue differt foliis minoribus 8.5–10.7 cm longis (nec 14–35 cm) et sub-tus in sicco laevibus (nec granulosis), floribusque stylo in-cluso (nec exserto) et antheris pro parte inclusis (nec omnino exsertis).

Etymology – The species name refers to the obovate leaves.

Tricalysia wilksii O.Lachenaud & Sonké, sp. nov.

Diagnosis – Foliis ellipticis basi acutis et glabris domatiis exceptis, calycisque lobis linearibus tubo aequantibus vel ex-cedentibus T. obstetrici N.Hallé similis, sed differt fructibus pedicellatis pericarpio tenue (nec sessilibus pericarpio inc-rassato), ovario dense pubescente (nec glabro), bracteolis in cupula breviora (0.8–1.3 mm, nec 1.5–2 mm) connatis, stipu-lis glabris (nec pubescentibus), foliisque nitidis et subtus in sicco laevibus (nec opacis et in sicco granulosis).

Etymology – The species name commemorates the British botanist Christopher Morris Wilks (13 July 1947–2 November 2008), a specialist of Central African trees, and one of the collectors of this plant.

Olivier Lachenaud, Tariq Stévart and Bonaventure Sonké. 2020. Three New Species of Tricalysia (Rubiaceae) from Atlantic Central Africa. Plant Ecology and Evolution. 153(2); 257-266. DOI: 10.5091/plecevo.2020.1670