Dipterocarpus costulatus is known by locals as keruing kipas. Keruing is the vernacular name for the genus Dipterocarpus while kipas is the Malay word for fan. The common name of this species is associated with its conspicuous ridged leaves which resemble the corrugated surface of a palm fan commonly used during grilling of satay or a traditional hand-held fan.
In Negeri Sembilan, D. costulatus is also known as keruing mara kluang and keruing pekat. However, both vernacular names are also shared by other Dipterocarpus species. For example, keruing mara keluang is also a vernacular name for D. costatus while keruing pekat also refers to D. grandiflorus, D. rigidus and D. verrucosus. The Malay word pekat means thick which refers to the viscosity or consistency of the oil produced from the wood of all of the above mentioned species (Symington et al., 2004). Thus, to avoid confusion keruing kipas has been chosen as the preferred vernacular name for D. costulatus.
This species is an emergent tree that can grow up to 1.2 m dbh and 50 m tall. It has a grey bole and patchily peeling bark that is covered with lenticels. The leaf is thick and has a leather-like texture. The leaf blade is broadly elliptic to ovate, measuring 12–20 X 7–14 cm. The stipules are greenish white and can measure up to 16 X 2 cm. The flowers are typical Dipterocarpus flowers, with 5 pinkish cream petals measuring about 3 X 5 cm. The fruits have 2 major calyx lobes of 20 X 4 cm and another 3 minor calyx lobes of 0.7 X 0.6 cm (Ashton et al., 2004).
Dipterocarpus costulatus is native to Sumatra, Peninsular Malaysia, Singapore, and Borneo. Ashton et al. (2004) stated that the species is common in the peninsula but infrequently found in Sabah while Julia et al. (2014) reported that this species is widely scattered throughout Sarawak’s southwest.
Its preferred habitat is lowland mixed dipterocarp forest that can sometimes be subjected to inundation. However, it can also be found on higher areas, as it has been recorded on a hill up to 600 m elevation in Bubu Forest Reserve in Perak (Symington et al., 2004).
Like other Dipterocarpus spp. such as D. crinitus and D. grandiflorus, the timber of D. costulatus locally known as keruing, is classified as medium hardwood, which has a high commercial value. The timber is used for heavy construction, boat building and flooring. In addition, after appropriate treatment, the timber can be used to build bridges, railway sleepers and power-line poles (Malaysian Timber Council, n.d.).
According to Symington (2004) the major threat for D. costulatus is forest conversion which can lead to habitat loss. In Malaysia, it is categorised as Near Threatened (NT); the populations are still well represented in Totally Protected Areas of Peninsular Malaysia and Sarawak (Chua et al., 2010; Julia et al., 2014). The global conservation status for this species is also Near Threatened (NT) as the areas where this species grows is considered as threatened habitats (Barstow, 2019).
A living collection of D. costulatus can be observed at the Dipterocarp Arboretum of the Forest Research Institute Malaysia at Kepong, Selangor.
