PlantaeDB Logo
Login Sign-up

Genus Dialium in Subfamily Dialioideae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

Dialium L. belongs to Fabaceae and, per APG IV (APG IV, 2016), is placed in subfamily Dialioideae. The genus contains about 40 accepted species (POWO, 2024) occurring in tropical Africa, Madagascar, SE Asia and the Neotropics. The type species designated by Linnaeus is Dialium indum L. (POWO, 2024).

Trees of Dialium are generally large, often with buttressed trunks. Leaves are paripinnate, bearing 2–6 opposite, entire leaflets, and small caducous stipules. Inflorescences appear as axillary or terminal panicles bearing numerous minute flowers that lack petals; the calyx forms a shallow cup and the corolla is reduced or absent (Bruneau et al., 2020). Ten free stamens surround a superior, monocarpellary ovary that contains a single ovule with basal placentation. Fruits are indehiscent legumes with a thick woody pericarp, usually containing one or two large seeds.

Centers of species richness occur in West African rainforests, where endemics such as Dialium dinklagei are common, and in Madagascar, which hosts several endemic taxa (POWO, 2024). Additional diversity is found in Southeast Asia, with D. indum ranging from India to the Malay Peninsula, and in the Amazon basin, represented by D. guianense. Most species occupy lowland tropical forest, often along river margins, from sea level up to roughly 1,200 m in elevation.

Flowers are visited by small insects and, in some species, are wind‑mediated, although detailed pollination studies are limited (Bruneau et al., 2020). Fleshy pericarp attract birds and mammals that disperse the seeds, and several taxa have reported chromosome counts of 2n = 24, indicating a base number of x = 12 (Lowe & Turner, 2020).

Molecular phylogenies place Dialium in a distinct clade within Dialioideae, separate from other legume groups (Bruneau et al., 2020). No formal subgenera are universally accepted, although some authors have proposed sectional divisions based on fruit morphology, a treatment not fully supported by recent analyses (WFO, 2024). Recent revisions have synonymized certain African species with Asian taxa, but most checklists retain them as separate entities (WFO, 2024).

Several species produce edible fruits used locally, while the timber of D. guianense and related taxa is valued for its density and durability. A few taxa, such as D. madagascariensis, are cultivated as ornamental shade trees in tropical gardens.

Habitat loss and forest fragmentation threaten many Dialium populations; several species are listed as Endangered or Vulnerable in national red‑lists. Continued protection of primary forests and development of ex situ conservation measures will be essential to preserve the genus.

Pick a Species to see its components: