Plant Ecology and Evolution 151(3): 442-448, doi: 10.5091/plecevo.2018.1523
Ixora kalehensis, a new Rubiaceae species from the Democratic Republic of the Congo
expand article infoPetra De Block
‡ Meise Botanic Garden, Nieuwelaan 38, BE-1860 Meise, Belgium
Open Access

Background – The rain forest genus Ixora currently comprises 37 species in Continental Africa. Within the framework of a treatment of the genus for the Flore d’Afrique centrale, a new species is described from D.R. Congo, despite its being known from only two specimens.

Methods – Standard methods of herbarium taxonomy are followed.

Key resultsIxora kalehensis De Block, a new species from the Central Forest District in D.R. Congo, is described and illustrated. Ixora kalehensis remains under-collected and relatively poorly known but can nevertheless easily be distinguished from other Ixora species. The most distinctive character is the colour of the dried leaves: blackish on the upper surface and vivid brown on the lower surface. Other important characters are the small-sized, compact and sessile inflorescences and the large tree habit. The species is only known from two specimens collected in the 1950s and its preliminary IUCN status is Endangered (EN B2ab(iii)). The lack of more recent herbarium material highlights that the collecting effort in D.R. Congo remains substandard. It is hoped that the formal description of Ixora kalehensis will draw attention of international and local collectors and will result in more material and greater knowledge of the species. The description of this species brings the number of Ixora species to thirteen for central Africa (D.R. Congo, Rwanda and Burundi) and to twelve for D.R. Congo. An identification key to the species of D.R. Congo is provided.

Central Forest District, D.R. Congo, Ixora, Ixora kalehensis, preliminary IUCN assessment


  • Anonymous (1962) Systematics Association committee for descriptive biological terminology. II. Terminology of simple symmetrical plane shapes (chart 1). Taxon 11: 145–156.
  • Aveling C. (2010) World Heritage in the Congo Basin. Paris, UNESCO World Heritage Centre.
  • Bamps P. (1982) Flore d’Afrique centrale (Zaire - Rwanda - Burundi). Répertoire des lieux de récolte. Meise, Jardin botanique national de Belgique.
  • Campbell D.G., Hammond H.D. (1989) Floristic inventory of tropical countries. The status of plant systematics, collections, and vegetation, plus recommendations for the future. New York, New York Botanical Garden.
  • Cocquyt C., Taylor J.C. (2015) New and interesting Surirella taxa (Surirellaceae, Bacillariophyta) from the Congo Basin (D.R. Congo). European Journal of Taxonomy 133: 1–15.
  • Davis A.P., Govaerts R., Bridson D.M., Ruhsam M., Moat J., Brummitt N.A. (2009) Global assessment of distribution, diversity, endemism, and taxonomic effort in the Rubiaceae. Annals of the Missouri Botanical Garden 96: 68–78.
  • De Block P. (1998) The African species of Ixora (Rubiaceae-Pavetteae). Opera Botanica Belgica 9: 1–218.
  • De Block P. (2008) Synopsis of the uniflorous Madagascan Ixora (Rubiaceae) species belonging to section Microthamnus. Belgian Journal of Botany 141: 141–156.
  • De Haan M., Cocquyt C., Tice A., Zahn G., Spiegel F.W. (2014) First records of Protosteloid Amoebae (Eumycetozoa) from the Democratic Republic of the Congo. Plant Ecology and Evolution 147: 85–92.
  • De Vogel E.F. (1987) Manual of herbarium taxonomy: theory and practice. Indonesia, UNESCO.
  • Doumenge C. (1990) La conservation des écosystèmes forestiers du Zaire. Gland & Cambridge, IUCN.
  • Hepper F.N. (1979) Second edition of the map showing the extent of floristic exploration in Africa south of the Sahara. In: Kunkel G. (ed.) Taxonomic aspects of African economic botany: Proceedings of the IX Plenary Meeting of AETFAT, Las Palmas de Gran Canaria, 18–23 March, 1978: 157–162. Las Palmas, Perez Galdoz.
  • IUCN (2018) Guidelines for Using the IUCN Red List Categories and Criteria. Version 13. Available from [accessed 1 Apr. 2018].
  • Küper W., Sommer J.H., Lovett J.C., Barthlott W. (2006) Deficiency in African plant distribution data – missing pieces of the puzzle. Botanical Journal of the Linnean Society 150: 355–368.
  • Mouly A., Razafimandimbison S.G., Florence J., Jérémie J., Bremer B. (2009a) Paraphyly of “Ixora” and new tribal delimitation of Ixoreae (Rubiaceae): Inference from combined chloroplast (rps16, rbcL, and trnT-F) sequence data. Annals of the Missouri Botanical Garden 96: 146–160.
  • Mouly A., Razafimandimbison S.G., Khodabandeh A., Bremer B. (2009b) Phylogeny and classification of the species-rich pantropical showy genus Ixora (Rubiaceae-Ixoreae) with implications of geographical monophyletic units and hybrids. American Journal of Botany 96: 686–706.
  • Norton E. (2018) In Memoriam: Deadliest attack on Virunga Staff in Park’s recent history brings total ranger deaths to 175. Available from [accessed 10 Apr. 2018]
  • Puff C., Robbrecht E., Buchner R., De Block P. (1996) Survey of secondary pollen presentation in the Rubiaceae. Opera Botanica Belgica 7: 369–402.
  • Robbrecht E. (1988) Tropical woody Rubiaceae: Characteristic features and progressions; Contributions to a new subfamilial classification. Opera Botanica Belgica 1: 1–271.
  • Robbrecht R., Lejoly J. (1982) Une espèce nouvelle d’Ixora (Rubiaceae – Coffeeae) du Zaire. Bulletin du Jardin botanique national de Belgique 52: 487–489.
  • Sosef M.S.M., Dauby G., Blach-Overgaard A., van der Burgt X., Catarino L., Damen T., Deblauwe V., Dessein S., Dransfield J., Droissart V., Duarte M.C,. Engledow H., Fadeur G., Figueira R., Gereau R.E., Hardy O.J., Harris D.J., de Heij J., Janssens S., Klomberg Y., Ley A.C., Mackinder B.A., Meerts P., van de Poel J.L., Sonké B., Stévart T., Stoffelen P., Svenning J-C., Sepulchre P., Zaiss R., Wieringa J.J., Couvreur T.L.P. (2017) Exploring the floristic diversity of tropical Africa. BMC Biology 15: 1–15. https://doi:
  • Stropp J., Ladle R.J., Malhado M., Ana C., Hortal J., Gaffuri J., Temperley W.H., Skøien J.O., Mayaux P. (2016) Mapping ignorance: 300 years of collecting flowering plants in Africa. Global Ecology and Biogeography 25: 1085–1096.
  • Taplin J.R.D., Lovett J.C. (2003) Can we predict centres of plant species richness and rarity from environmental variables in sub-Saharan Africa? Botanical Journal of the Linnean Society 142: 187–197.
  • Thiers B. (continuously updated) Index Herbariorum: a global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. Available from [accessed 1 Apr. 2018]
  • UNESCO (2017a) State of Conservation: Virunga National Park (Democratic Republic of the Congo). Available from [accessed 1 Apr. 2018].
  • UNESCO (2017b) State of Conservation: Kahuzi-Biega National Park (Democratic Republic of the Congo). Available from [accessed 1 Apr. 2018].