Genus Eurycoma in Family Simaroubaceae
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).
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Genus Description
Suggest a correction!Genus Overview: Eurycoma
The genus Eurycoma belongs to Simaroubaceae and comprises approximately seven species of dioecious trees and shrubs native to Malesia and northern Thailand. Its distribution extends across Borneo, Sumatra, Peninsular Malaysia, and parts of Thailand, with most taxa occurring in lowland tropical forests from sea level to mid elevations. The type species is Eurycoma longifolia, which provides the name-bearing basis for the genus (WFO, 2024; POWO, 2024).
Diagnostic morphology distinguishes Eurycoma by its tall, mostly unbranched trunks and long, pinnately compound leaves that bear numerous small leaflets with entire margins. Young shoots and petioles often carry a dense brown indumentum, and axillary scales replace conspicuous stipules. Plants are functionally dioecious. Inflorescences are paniculate, bearing numerous tiny unisexual flowers with reduced or absent petals in female plants and fewer, sometimes slightly larger petals in males. Carpels are free, and ovules are pendulous with axile placentation. The fruit is a drupaceous structure with thin flesh and a hard endocarp, separating into two mericarps; seeds are dispersed by birds and mammals (van der Burgt et al., 2012; WFO, 2024).
Species diversity and centers of diversity occur in Borneo and the Malay Peninsula, where several narrow endemics occur in lowland to hill forests on well-drained soils. Most species are tied to primary forest habitats, with one species extending to northern Thailand (van der Burgt et al., 2012). The geographic pattern is essentially Malesian.
Intrinsic biology reflects classic zoochorous dispersal associated with brightly colored fruits; the floral biology remains under-documented (van der Burgt et al., 2012). A base chromosome number of x = 18 has been reported (Kong et al., 2016).
Taxonomy and phylogeny recognize several species in Peninsular Malaysia, Borneo, and northern Thailand, and minor synonymizations continue to be resolved. Nooteboom (1962) provided an influential treatment, and recent revisions have refined circumscriptions in Borneo and the Malay Peninsula (van der Burgt et al., 2012). Alternative treatments persist in regional floras and checklists; the broader genus-level placement within Simaroubaceae remains widely accepted (APG IV, 2016; WFO, 2024).
Human relevance centers on horticulture and timber; Eurycoma longifolia is valued for shade or ornamental planting, and the hard wood is locally used. Harvesting pressure for cultural uses does not equate to medicinal claims here.
Conservation and outlook are constrained by habitat loss and local overharvesting; updated red‑list assessments and population monitoring remain research priorities (POWO, 2024).
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Eurycoma apiculata (A.W.Benn.)
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Eurycoma harmandiana (Pierre)
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Eurycoma longifolia (Jack)
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