Genus Anisoptera in Tribe Dipterocarpeae

Genus Description

Anisoptera (Korth.) is a genus of medium to large trees in the family Dipterocarpaceae, comprising about twelve to fifteen accepted species (POWO, 2024; WFO, 2024). The type species is Anisoptera costata Korth., the original taxon for the genus. Members are restricted to tropical lowland rainforests of Southeast Asia, from the Malay Peninsula through Borneo, Sumatra, the Philippines and New Guinea, occurring in both terra firme and peatswamp forests up to roughly 800 m. The genus is distinguished by several characters: trees with buttressed trunks and caducous stipules, simple alternate leaves that are entire and often have a dense yellowish indumentum on the lower surface, and panicles that are terminal or axillary bearing numerous five‑parted flowers. The calyx lobes are unequal, the larger forming a long wing while the smaller remains short, giving the fruit a characteristic two‑winged samara (Symington, 2004). The ovary is superior and five‑locular with two ovules per locule; the fruit is a dry, winged achene that dehisces at maturity. Anisoptera reaches its highest richness in Borneo and Sumatra, with narrow endemics such as A. laevis in the Philippines and A. polyandra in northern Borneo. Typical habitats include primary dipterocarp forest, kerangas, and freshwater swamp; the genus is absent from montane zones. Pollination is presumed largely anemophilous, though nectariferous sepals suggest occasional insect assistance (Gale et al., 2017). The winged fruit is wind‑mediated, allowing long‑distance colonization of suitable gaps. Chromosome numbers are rarely reported and a stable base number for the genus is not yet established. Molecular phylogenies confirm Anisoptera as a monophyletic group within Dipterocarpoideae, sister to Vatica (Lee et al., 2022). The genus is accepted without subgeneric division in most modern treatments, although a few authors (e.g., Symington, 2004) have proposed a broader Shorea concept that would include Anisoptera; this view is not followed in major databases (POWO, 2024). Several species provide high‑quality timber used in construction and furniture, and resin is harvested for varnish; the trees are occasionally cultivated in botanical gardens but have limited ornamental use. Habitat loss from logging, oil‑palm conversion and peatland drainage threatens many populations, and detailed assessments of reproductive biology and genetic diversity remain scarce. Continued protection of remaining primary forest fragments and implementation of targeted restoration programs will be essential for the long‑term persistence of Anisoptera species.

• Anisoptera sect. Anisoptera ()
• Anisoptera sect. Glabrae (F.Heim)