Systematics and Conservation of the Tropical African Genus Hymenostegia (Detarieae: Caesalpinioideae: Leguminosae)
Kew has been leading on a multidisciplinary study of the exclusively tropical African forest genus Hymenostegia to clarify its classification and to assess the conservation status of all species, many of which are rare.
Hymenostegia ngouniensis: flowers and foliage. Copyright: University of Wageningen
The forests of Tropical Africa contain more species of Leguminosae (legumes) than any other flowering plant family and tree species of legume subfamily Caesalpinioideae often dominate the rainforest. Yet conservation of Africa’s forests continues to be hampered by the lack of taxonomic knowledge of these legume giants.
This study was prompted by the need to describe four Cameroonian endemic legume tree species as new to science. Prior to this study, a major impediment to their description was uncertainty as to their correct generic placement. Their correct generic assignment could be determined either to Hymenostegia Harms or to Talbotiella Baker f. but the boundary between the two genera was unclear. Morphological, nucleotide sequence and pollen surface characters were studied to resolve the question: Is Talbotiella distinct from Hymenostegia or are they congeneric? The data supported maintaining the genera as distinct and the correct placement of the new species is in Talbotiella and indicated the need to transfer Hymenostegia breteleri to Talbotiella. In addition the data revealed the extensive heterogeneous nature of Hymenostegia. As currently circumscribed about half of the species constitute a natural group but the others not only do not belong in Hymenostegia, but also do not belong together. Possibly as many as four different generic placements may be needed for these erroneously assigned species. To determine the correct placement of these misplaced species, multiple data sets (morphology, pollen, wood anatomy and nucleotide sequences) are being generated and analysed.
The outputs of the project are being published in peer-reviewed journals, conservation checklists and IUCN Red Data books.
Key publications 2006-2011
- Mackinder, B., Wieringa, J. & Burgt, X. van der. (2010). A revision of the genus Talbotiella Baker f. (Caesalpinioideae: Leguminosae). Kew Bulletin 65 (3): 401-420.
- Mackinder, B. (2011). Leguminosae subfamily Caesalpinioideae. In Onana, J.M. & Cheek, M. (eds) Red Data Book. The flowering plants of Cameroon IUCN global sssessments. London: Royal Botanic Gardens, Kew. 176 – 188, maps 470 – 475.
- Wieringa, J.J. & Mackinder, B.A. (----). Novitates Gabonensis 79: Hymenostegia elegans and Hymenostegia robusta, two new threatened caesalpinioid legume species from Gabon. Nordic Journal of Botany (in press in 2011)
Student theses 2006-2011
- O’ Donnell, K. (2008). A phylogenetic study of Hymenostegia and Talbotiella. University of Edinburgh. BSc
- Twinning, F. (2010). The contribution of wood anatomy to the classification of Hymenostegia sensu lato. University of Edinburgh. MSc.
Project partners and collaborators
Herbier Nationals du Gabon
University of Montreal, Canada