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Genus Bonamia in Family Convolvulaceae

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

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Bonamia (Thouars) is placed in Convolvulaceae and comprises approximately 70 species of mostly lianas, shrubs, and herbs, with a pantropical distribution and secondary centers in tropical Africa and Madagascar (Robertson, 1972; Austin and Staples, 1983). The genus includes one arborescent species, the critically endangered Bonamia spectabilis from Mauritius, which is often cited as the type of the genus (POWO, 2024; Verdcourt, 1957).

Diagnostic morphology is defined by typically twining or scrambling habits, herbaceous to woody stems, and entire leaves that are sometimes leathery. Trichomes are usually simple, and stipules are absent. Flowers are borne in axillary, cymose to racemose inflorescences, with rotate to campanulate corollas that are white or pink and often have a deep-coloured throat. The androecium includes five stamens attached to the corolla tube, and the ovary is superior with usually two fused carpels and a style with a single capitate stigma. Fruits are globose to ovoid capsules that dehisce longitudinally into valves, exposing seeds that are often pubescent (Robertson, 1972; Austin and Staples, 1983; Hallier, 1893).

Diversity and range are highest in tropical Africa, Madagascar, and the Mascarene Islands, with additional diversity in Southeast Asia and Australia. Endemism is notable in Madagascar and the Mascarene archipelago. Species occupy a variety of habitats from coastal scrub and seasonally dry forests to open savanna and woodland, from low elevations to around 1500 m, showing considerable ecological breadth (Robertson, 1972; GBIF, 2024).

Intrinsic biology is known primarily from floral traits; white to pink corollas and open floral morphology suggest pollination by generalist insects, especially bees, although specific data remain sparse for most species. Chromosome numbers are varied across Convolvulaceae and specific base numbers for Bonamia are not consistently established (Staples, 2006).

Taxonomy and phylogeny have been stable since the broad recircumscription that incorporated Brewerea and Stylochiton sensu Hallier, leading to a unified Bonamia (Robertson, 1972). Treatments such as Robertson’s are widely followed; Bonamia remains monophyletic in several molecular studies, but comprehensive suprageneric relationships across Convolvulaceae continue to be refined (Austin et al., 2018). Alternative approaches that split African species into separate genera are occasionally applied but not widely adopted (Austin and Staples, 1983; Staples et al., 2015).

Human relevance is limited; the genus offers little economic importance beyond occasional ornamental use and a minor role in local horticulture. B. spectabilis exemplifies a charismatic, threatened member that attracts conservation interest (POWO, 2024; Verdcourt, 1957).

Conservation and outlook are uneven across the range. B. spectabilis is highly threatened, and B. kochiana is considered extinct on Mauritius; habitat loss and small-population dynamics are common concerns. Targeted field surveys and taxonomic clarity remain priorities to guide conservation actions (POWO, 2024; Robertson, 1972).

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