Atractocarpus is a genus of roughly 40 species of flowering plants in the family Rubiaceae (order Gentianales), commonly known in Australia as native gardenias. The genus was formally defined by botanists Rudolf Schlechter and Kurt Krause in 1908, with Atractocarpus bracteatus — a New Caledonian endemic — as the type species. A pivotal revision by Australian botanist Christopher Puttock in 1999 substantially expanded the genus by transferring numerous species previously placed in the wastebasket genera Randia and Gardenia, and by sinking the small genera Sukunia, Trukia, Neofranciella, and Sulitia into Atractocarpus.
Members of the genus are dioecious or gynodioecious spineless small trees with furrowed or smooth bark and branchlets bearing distinctive lenticel protrusions. Leaves are opposite or whorled in threes or fours, entire, and may bear domatia in the vein angles. The inflorescences are many-flowered thyroids or dichasial cymes, occasionally reduced to solitary flowers; the 5-merous flowers are white or cream, turning brown with age, and the fruit is a berry containing few to many dark-brown seeds — the spindle-shaped fruit of the type species giving the genus its name.
The genus ranges across the Asia-Pacific: seven species are native to Australia (six endemic, occurring in Queensland and New South Wales), with additional species in the Federated States of Micronesia, the Philippines, New Guinea, the Solomon Islands, Vanuatu, New Caledonia, Fiji, Tonga, and east to Tahiti. All species inhabit lowland tropical vegetation, primarily simple mesophyll vine forests, swamp forests, and vine thickets. Notable Australian members include A. fitzalanii and A. chartaceus, both valued as garden plants.
Etymology
The name Atractocarpus combines the Ancient Greek words atractos ("spindle") and karpos ("fruit"), a reference to the distinctive spindle-shaped fruit of the type species, Atractocarpus bracteatus.
Distribution
Atractocarpus occurs across a broad arc of the tropical Asia-Pacific region, from Australia northward through New Guinea, the Philippines, and Micronesia to the Solomon Islands, Vanuatu, New Caledonia, Fiji, Tonga, and Tahiti. In Australia, seven species are native, six of them endemic, found in Queensland and New South Wales.
Ecology
All species of Atractocarpus are restricted to lowland tropical vegetation, particularly simple mesophyll vine forests, swamp forests, and marine semi-deciduous vine thickets.
Taxonomy Notes
The genus was established by Schlechter and Krause in 1908. Prior to Puttock's 1999 revision, many of its species had been misplaced in the large wastebasket genera Randia and Gardenia. Puttock's revision transferred Australian Randia species not closely related to Neotropical Randia, and synonymised Sukunia, Trukia, Neofranciella, and Sulitia into Atractocarpus, bringing the genus to its current circumscription of around 40 species. The genus belongs to the tribe Gardenieae within Rubiaceae.
