Diploglottis is a genus of 11 species of trees in the family Sapindaceae — the lychee and maple family — placed in the order Sapindales. The genus is almost entirely endemic to eastern Australia, with the great majority of species restricted to the Wet Tropics bioregion of Queensland; one species, D. diphyllostegia, extends into New Guinea, while D. australis and D. campbellii reach as far south as northern New South Wales.
Plants in the genus are small to large trees, often with fluted and multi-stemmed trunks and branchlets bearing lenticels. The leaves are alternate and compound paripinnate, with leaflets arranged oppositely or alternately along the rachis, sometimes quite large and stiff. Inflorescences are axillary panicles bearing small, slightly zygomorphic flowers that are polygamous — carrying both bisexual and unisexual flowers on the same plant. The calyx has five lobes and the corolla four or five petals with hairy, usually crested scales. Stamens number six to ten. The fruit is a two- or three-lobed capsule, and each seed is partly or fully enclosed in a fleshy, acidic bilobed aril.
Species in the genus are commonly called tamarinds — D. diphyllostegia is the northern tamarind, D. harpullioides the Babinda tamarind, and D. berniana Bernie's tamarind — though they bear no close relationship to the true tamarind, which belongs to the unrelated family Fabaceae. Diploglottis australis, the native tamarind, is planted as a street tree in the Northern Rivers region of New South Wales. Diploglottis campbellii, the small-leaved tamarind, is a rare and threatened species known from only about 42 mature wild trees across south-eastern Queensland and north-eastern New South Wales, though it is readily available from nurseries and its fruit is commercially produced as a bushfood.
Distribution
Diploglottis is centred on the Wet Tropics bioregion of north-eastern Queensland, with most of its 11 species endemic to eastern Australia. Diploglottis australis and D. campbellii extend south into northern New South Wales, and D. diphyllostegia is the sole species reaching beyond Australia into New Guinea. PlantNET records the broader range as eastern Malesia and New Caledonia in addition to Australia.
Ecology
Species grow in rainforest and subtropical to tropical forest environments along the eastern Australian seaboard, particularly in the Wet Tropics. The fleshy, acidic arils are adapted for seed dispersal, and the polygamous flower structure supports pollinator diversity. D. campbellii is critically restricted in wild populations, with a maximum of three trees per known site.
Cultural Uses
The acidic arils of Diploglottis fruit have long been used in Australia for drinks and jam-making. The fruit of D. campbellii (small-leaved tamarind) is commercially produced as a bushfood and sold in the Northern Rivers region of New South Wales. D. australis is planted as a street tree in Lismore and surrounding towns.
Conservation
Diploglottis campbellii is rare and threatened, with only approximately 42 known mature wild trees occurring in small populations across south-eastern Queensland and north-eastern New South Wales, each site supporting a maximum of three trees.
