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Genus Grewia in Family Malvaceae

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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Grewia L. (Malvaceae, subfamily Grewioideae) (APG, 2016) comprises about 160 species of shrubs, trees and lianas distributed across tropical and subtropical Africa, Asia, Madagascar and northern Australia, from lowland rainforest to dry woodland. The type species is Grewia orientalis L. (POWO, 2024).

Plants are characterised by simple, alternate leaves that are palmately veined, often three‑ to five‑nerved, with caducous stipules. Inflorescences are axillary or terminal cymes that may be reduced to solitary flowers. Flowers are five‑merous, bearing an epicalyx of five free or partially fused bracteoles, numerous free stamens, and a superior ovary that is typically five‑locular, each locule containing two ovules. The fruit is a fleshy schizocarp of two to five mericarps, each a drupaceous structure that encloses a single seed.

The genus reaches its highest richness in East Africa and Southeast Asia, with Madagascar harbouring roughly 70 endemic taxa. Species occupy a range of habitats from coastal scrub to montane forest up to 2000 m, reflecting the genus’ adaptability to both moist and seasonally dry environments.

Pollination is mainly by insects, especially bees and flies, while the fleshy mericarps are dispersed by birds and small mammals, facilitating long‑distance gene flow. Cytological data indicate a base chromosome number of x = 9, with reports of 2n = 36, 54 or 72 in different species (Khan et al., 2018).

Traditional sectional treatments separate subg. Grewia and subg. Microgrewia, the latter sometimes treated as a distinct genus. Molecular phylogenies (Affre et al., 2021) support the monophyly of Grewia s.s. while revealing geographically coherent clades that may merit sectional recognition. Alternative classifications retaining Microgrewia as distinct are still accepted by some databases, reflecting ongoing debate about species limits rather than conflicting molecular evidence.

Several species produce edible fruits, notably Grewia asiatica (phalsa), which is harvested locally and cultivated as an ornamental. The wood of larger trees is used for small‑scale furniture, while a few species, such as Grewia occidentalis, are considered invasive in parts of Australia (Mackenzie & Lee, 2020).

Habitat loss and over‑harvest threaten many taxa; the IUCN Red List includes many data‑deficient assessments. Continued taxonomic clarification, population monitoring and habitat protection will be essential to secure the genus’ future.

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