Casearia is a large genus of shrubs and small trees in the family Salicaceae, order Malpighiales, comprising approximately 180 species distributed across tropical and subtropical regions of Africa, Asia, Australia, North and South America, and the Pacific islands. The genus was described by Nikolaus Joseph von Jacquin in 1760 and has undergone considerable reclassification over its history — it was long placed in the Flacourtiaceae under the Cronquist system, and earlier in the Samydaceae, before molecular phylogenetics moved Salicaceae to encompass these former families.
Plants are typically shrubs or small trees with alternate, petiolate leaves that characteristically bear pellucid glandular dots and lines throughout the blade, visible at 10× magnification when held against light. Stipules are usually small and early-caducous. The flowers are perigynous, bisexual, and small, typically clustered in axillary fascicles. Petals are absent; sepals number 4 or 5; a cuplike disk is adnate to the inside of the calyx tube; stamens number 6–12. The ovary is superior and 1-loculed. Fruits are fleshy to leathery capsules — globose to 3-angled when fresh and mostly 6-ribbed when dry — that split into 2–4 valves. Seeds are arillate, with a brightly colored, soft aril.
Several species have economic or ecological significance. Casearia decandra and C. sylvestris are valued as honey plants, and C. sylvestris serves as a larval food plant for the two-barred flasher butterfly (Astraptes fulgerator). Deforestation has driven multiple species toward rarity or extinction: C. quinduensis of Colombia is regarded as likely extinct, and C. tinifolia from Mauritius appears to have disappeared around 1976.
Distribution
Casearia is pantropical, with roughly 180 species distributed across tropical and subtropical Africa, Asia (including India, China, Southeast Asia, and the Pacific islands), Australia, and North and South America. Seven species are recorded from China, where the genus extends into subtropical montane forests.
Taxonomy Notes
Casearia was described by Nikolaus Joseph von Jacquin in 1760 (Enum. Syst. Pl. 4: 21). The genus was historically placed in the Flacourtiaceae under the Cronquist classification system, and earlier in the Samydaceae; it is now accepted within the Salicaceae (order Malpighiales) following molecular phylogenetic revisions. Synonyms include Antigona Vellozo, Athenaea Schreber (1789), and Vareca Gaertner.
Conservation
Deforestation has pushed several Casearia species toward rarity or extinction. Casearia quinduensis of Colombia is considered possibly extinct, and Casearia tinifolia, endemic to Mauritius, appears to have gone extinct around 1976. The genus illustrates the vulnerability of island and narrow-endemic tropical tree species to habitat loss.
