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Genus Prestonia in Subtribe Prestoniinae

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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Prestonia (R.Br.) is a Neotropical genus in the Apocynaceae, subfamily Asclepiadoideae (APG IV, 2016). Approximately 145 species are recognized (POWO, 2024), ranging from lowland rainforest to montane cloud forest and occasionally dry savanna. The type species, Prestonia quinquangularis R.Br., was designated in the original 1810 description (POWO, 2024).

Plants are woody vines or shrubs, often twining; leaves opposite, simple, lacking stipules, with a prominent latex; inflorescences are terminal or axillary dichasia; flowers large, corolla campanulate to funnel‑shaped, lobes twisted in bud, bearing a double corona typical of Asclepiadoideae; the gynostegium is formed by the fused stamens and style head; each flower produces a pair of follicular fruit, each with many seeds bearing a long silky coma for wind dispersal. Flowers range from white to pink or violet, often with a conspicuous throat, and may open sequentially along the inflorescence axis.

The genus reaches its highest richness in the Guiana Shield and western Amazon Basin, with a secondary centre in the Northern Andes. Several narrow endemics are restricted to limestone outcrops or cloud forests above 1500 m. The typical habitat is moist tropical forest, but a few species occupy seasonally dry woodland. Disjunct populations also occur in the Venezuelan Guayana highlands and Central America.

Observations indicate that pollination is entomophilous, likely involving moths and butterflies attracted to the fragrant flowers. The abundant latex deters herbivores. Seed morphology with a tufted coma suggests wind dispersal. Chromosome counts are sparse; a base number of x = 11 has been reported for a few species (Alonso et al., 2022).

Prestonia is placed in the tribe Asclepiadeae, subtribe Marsdeninae (Fishbein et al., 2018). Recent molecular analyses confirm the genus as monophyletic, while also indicating that some species previously assigned to Prestonia belong to the Pentatropis clade (Fishbein et al., 2018). The genus is currently maintained distinct in major checklists (WFO, 2024; POWO, 2024).

A few species such as Prestonia macrocalyx are cultivated for their ornamental, fragrant flowers, but the genus lacks major economic crops or timber value. Some weedy vines appear in disturbed forest edges.

Many Prestonia taxa are locally rare and threatened by habitat conversion; however, many are still relatively widespread. Future work combining field surveys and phylogenetic data will be essential for assessing extinction risk and informing conservation planning.

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