Possible horizontal gene transfer: Virectaria stellata (Sabiceeae-Rubiaceae), a new sandstone cliff species from the Republic of Guinea with stellate hairs recorded for the first time in the Rubiaceae
From Firenze University Press Journal: Journal of Plant Taxonomy and Geography (Webbia)
Faya Julien Simbiano, Herbier National de Guinée, Université Gamal Abdel Nasser de Conakry
Xander M. van der Burgt, Herbarium, Royal Botanic Gardens, Kew, Richmond
Iain Darbyshire, Herbarium, Royal Botanic Gardens, Kew, Richmond
Pepe M. Haba, Société des Mines de Mandiana, Kankan
Gbamon Konomou, Herbier National de Guinée, Université Gamal Abdel Nasser de Conakry
Martin Cheek, Herbarium, Royal Botanic Gardens, Kew, Richmond
Charlotte Couch, Herbarium, Royal Botanic Gardens, Kew, Richmond
Sékou Magassouba, Herbier National de Guinée, Université Gamal Abdel Nasser de Conakry
Among the specimens collected during botanical surveys aimed at estab-lishing Important Plant Areas in the Republic of Guinea (henceforth Guinea; Couch et al. 2019; Darbyshire et al. 2017) was a new spe-cies of Virectaria Bremek. (Rubiaceae: Sabiceeae) found on the Benna Plateau and Mont Kouroula in the prefectures Forécariah and Kindia respectively. The new material from Guinea was placed in Virectaria due to the presence of several traits that characterise this morphologically isolated genus: the stigma is unlobed and capitate and only slightly wider than the style; both style and stamens are exserted about as long as the corolla lobes; aestiva-tion simply valvate; one of the two fruit valves is decidu-ous, the other persistent; and the floral disc is cone-like, accrescent, and dehiscing into two halves in fruit.Virectaria Bremek. (Bremekamp 1952) was erect-ed to contain most of the African species previously referred to the genus Virecta L.f. (Linnaeus 1782). The International Plant Names Index (IPNI 2024) lists 28 names under Virecta. The neotropical Virecta names, together with the type of Virecta, V. biflora L.f., are referrable to Sipanea Aubl., a genus of about 19 spe-cies in northern S. America and C. America. The Asian names of Virecta refer to Ophiorrhiza L., a genus of about 320 species occurring from India to N.E. Australia and Japan. Some African Virecta names are referred to Pentas Benth. (e.g. Virecta lanceolata Forssk.), Parapen-tas Bremek. (Virecta setigera Hiern); or Sabicea Aubl. (Virecta lutea G. Don). Verdcourt (1953) revised Virecta-ria, recognising five species from the 12 Virecta names attributable to the genus Virectaria.Virectaria was placed in Ophiorhizeae by Breme-kamp or was often formerly place in a loosely circum-scribed Hedyotideae (both Rubioideae) e.g. Hepper (1963), together with Oldenlandia L., Pentas, Para-pentas and Hekistocarpa Hook.f. However, Verdcourt (1953) did not concur and erected the mono-generic tribe Virectarieae (Verdcourt 1975) to accommodate the genus. He also recognised that it did not belong to Rubioideae but to Cinchonoideae/Henriquezieae. Currently eight species are recognised, V. angustifolia (Hiern) Bremek., V. belingana N. Hallé, V. herbacoursii N. Hallé, V. major (K.Schum.)Verdc., V. multiflora (Sm.)Bremek., V. salicoides (C.H.Wright) Bremek. and V. tenella J.B.Hall. Seven infraspecific taxa are also accept-ed (Dessein et al. 2001b).Publication and molecular placement of the mono-typic Socotran Tamridaea Thulin & B. Bremer showed a close relationship with Virectaria and the placement of these two genera in an expanded Sabiceeae (Bremer & Thulin 1998). Placement of Virectaria within the Sabi-ceeae was contested by Dessein et al. (2001a) on mor-phological grounds, and Virectaria was instead placed with Hekistocarpa and Tamridaea in an expanded Virec-tarieae near to Sabiceeae (Dessein et al. 2001b). However, more detailed subsequent molecular studies reconfirmed placement in Sabiceeae (Khan et al. 2008a; 2008b). The monotypic Cameroonian Hekistocarpa is sister to the three other genera of Sabiceeae, Socotran Tamridaea is sister to Virectaria, and these two genera are in turn sis-ter to the most species-diverse genus Sabicea which, with c. 167 species, extends from the Neotropics, through Africa and Madagascar, to Sri Lanka.In this paper we describe Virectaria stellata sp. nov., increasing the numbers of species in the genus in Guinea from two to three (Gosline et al. 2023a; 2023b). The new species is exceptional in the Rubiaceae in hav-ing stellate hairs, and further remarkable in that they include an unusual type of stellate hair otherwise known from some Acanthaceae.New, nationally endemic plant species continue to be steadily published from Guinea e.g. recently Casea-ria septandra Breteler & A.Baldé (Breteler & Baldé 2024, Salicaceae), Keita deniseae Cheek (Cheek et al. 2024, Olacaceae), Erianthemum nimbaense Jongkind andPhragmanthera cegeniana Jongkind (Jongkind 2023, Lor-anthaceae) and Gymnosiphon fonensis Cheek (Cheek et al. 2024, Burmanniaceae).
DOI: https://doi.org/10.36253/jopt-16523
Read Full Text: https://oaj.fupress.net/index.php/webbia/article/view/16523
