Genus Markhamia in Family Bignoniaceae

Genus Description

Markhamia (Seem. ex Baill.) in Bignoniaceae is a small, pantropical genus of about six species that occurs widely across tropical Africa and has established in parts of Southeast Asia and the Neotropics, primarily in riverine and secondary forest, savanna margins, and lowland to mid-elevation areas up to roughly 1,800 meters. The type species is Markhamia zanzibarica (K.Schum.) K.Schum. ex Sprague (G.I. Kania, 2006). It is a commonly planted ornamental, widely naturalized in the Neotropics and elsewhere, with M. lutea (Benth.) K.Schum. as the species most often seen in horticulture.

The plants are trees and shrubs with opposite, usually ternate or pinnate leaves; leaflets are typically elliptic to oblong, entire or slightly serrate, and may be glabrescent to densely pubescent, sometimes with scattered peltate scales, while stipules are small or absent. Inflorescences are terminal racemes or panicles bearing large, showy, zygomorphic flowers with a five‑lobed, campanulate corolla that is cream‑white to pale yellow with contrasting purple or maroon lines within the tube. The calyx is laterally spathaceous (split along one side); stamens are didynamous with one staminode, and the superior ovary is bicarpellate and bilocular, with axile placentation. The fruit is a long, flattened, woody capsule dehiscing along two valves; seeds are flat and broadly winged, facilitating wind dispersal.

Diversity and range center in tropical Africa, with multiple species from West to East Africa and Madagascar, and populations extending into Arabia; endemism is modest and not highly restricted, although several taxa are tied to riverine habitats. Major biogeographic patterns reflect generalist tropical African distributions with occasional long‑distance establishment via horticultural pathways.

Intrinsic biology remains poorly documented; pollination is presumed to involve bees attracted to the conspicuous flowers, and wind dispersal is evident from the fruit and seed morphology, but detailed field studies are scarce. A base chromosome number of x=16 is commonly reported in Bignoniaceae but requires verification for Markhamia before acceptance.

Taxonomy and phylogeny: G.I. Kania’s revision (2006) entrenched the circumscription of Markhamia and recognized two subgenera (Markhamia and Asteranthopsis), emphasizing fruit and seed characters (flattened, dehiscent capsule and winged seeds) to distinguish the genus from Dolichandrone, which produces more cylindrical, rarely flattened capsules. Subsequent global frameworks place Markhamia firmly within tribe Bignonieae (G.M. Machado et al., 2021), and the name is accepted in authoritative checklists (POWO, 2024; WFO, 2024). Alternative treatments, such as a broad Dolichandrone concept merging Markhamia or the recognition of “Astianthus” for some taxa, remain unresolved in specialized sources, and the present treatment follows Kania (2006) and recent phylogenies.

Human relevance: Markhamia lutea is a popular street and shade tree in tropical cities for its showy flowers and tolerances to pruning and urban conditions, and it sometimes invades riparian corridors in introduced regions (global assessments in IUCN, 2024; pest risk notes in CABI, 2023). No species are major timbers or food crops in native ranges.

Conservation and outlook: most taxa are assessed as Least Concern (IUCN, 2024), yet habitat degradation along waterways, along with the risk of invasive behavior in cultivation, warrants monitoring; prioritizing field studies on reproductive biology and gene flow would refine both conservation and management strategies.

• Markhamia lutea (K.Schum.)
• Markhamia obtusifolia (Sprague)
• Markhamia stipulata (Seem.)
• Markhamia tomentosa (K.Schum. ex Engl.)
• Markhamia zanzibarica (K.Schum.)