Guibourtia ehie (black hyedua)

Guibourtia ehie grows in African lowland forest. It occurs in the upper Guinea forest block, in Côte d'Ivoire, Liberia and Ghana, is absent from the more arid and unforested Dahomey interval and then reappears in the lower Guinea forest block in Nigeria, Cameroon, Equatorial Guinea and Gabon.

Herbarium specimen of Guibourtia ehie collected by A. Chevalier from the Ivory Coast in 1909 (Image: RBG Kew)

Guibourtia ehie is a forest tree up to 45 m high with a trunk up to 1 m in diameter. The leaves are composed of two asymmetrical leaflets, each shaped like a half-moon. The outer side of each leaflet is at least three times as broad as the inner side, ending in a long, curved tip. The white flowers are scented and arranged along short axes, which in turn are combined with other flowering ‘spikes’ to form a branched flowering structure, which measures up to 25 cm long. The fruits (pods) are flat and papery, and their surfaces are covered with a network of fine veins; each fruit contains a single seed. Some species of Guibourtia have resin in the leaves that appears as translucent yellow dots when the leaves are held to the light and/or seeds that bear an aril (a soft, fleshy and often colourful layer covering part or all of the external seed surface), but G. ehie has neither gland dots nor arils.

The leguminous genus Guibourtia is currently considered to comprise 14 species. Thirteen occur in tropical Africa, but G. hymenaeifolia is found only in the Neotropics. A group of organisms that are found on both sides of the Atlantic Ocean are said to have an amphi-Atlantic distribution. This distribution pattern is relatively unusual in legume tree genera and there has been some doubt as to whether the Neotropical and African Guibourtia species belong together. To explore this and other questions, Guibourtia is currently the subject of an MSc study by Kew botanist Frances Crawford (supervised by Reading University). Frances is using morphological and genetic (DNA) data to investigate the genus. Preliminary results indicate that the neotropical species is a true Guibourtia that arrived in the Neotropics from Africa by long distance dispersal.

Black hyedua is widespread in West Africa and several populations are known to occur within protected areas. However, its exploitation for timber could result in population decline. Based only on geographical range data from herbarium specimens, Guibourtia ehie is considered to be of Least Concern according to IUCN red list criteria (IUCN 2001). However, it was previously assessed as Vulnerable (as a result of an assessment arising from an African regional workshop in 1996), and further research and fieldwork are required to verify its true conservation status.

Conservation assessments carried out by Kew

Guibortia ehie is being monitored as part of the Sampled Red List Index Project, which aims to produce conservation assessments for a representative sample of the world’s plant species. This information will then be used to monitor trends in extinction risk and help focus conservation efforts where they are needed most.

Leaves of Guibourtia ehie (Image: © William Hawthorne)

Guibourtia ehie is mainly used for timber production, which is a popular substitute for rosewood (Dalbergia species). It is used for fine furniture and cabinetwork, turnery, decorative veneers and flooring. The bark exudes a gum if cut, but fresh gum is not produced in commercial quantities. However, ‘fossil’ resin (copal) is collected from the ground in parts of West Africa and made into sweet-smelling necklaces by local traders. In Nigeria, this resin is burnt for lighting.

Pressed and dried specimens of Guibourtia ehie are held in Kew’s Herbarium, where they are available to researchers from around the world by appointment. The details, including an image, of one of these specimens can be seen online in the Herbarium Catalogue.

Specimens of the wood and bark of black hyedua are held in Kew’s Economic Botany Collection, available to researchers by appointment.

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