Cossinia is a small genus of four species of rainforest trees belonging to the family Sapindaceae (order Sapindales). It is notable for its strikingly disjunct distribution: the four species are each endemic to widely separated island and coastal regions — the Mascarene Islands (Réunion and Mauritius) in the Indian Ocean, Queensland in eastern Australia, New Caledonia, and Fiji. This fragmented range makes Cossinia an example of a relict Gondwanan lineage scattered across the southwestern Pacific and Indian Ocean.
The genus grows naturally in rainforest habitats, including seasonally drought-prone rainforests and associated non-fire-adapted vegetation types. At least two of the four species face significant conservation pressure: Cossinia australiana, restricted to central-eastern and southeastern Queensland, holds national and state “Endangered” status in Australia, with its habitat having been extensively cleared and remaining under further threat. Cossinia trifoliata, endemic to New Caledonia, was assessed as Vulnerable to global extinction by the IUCN in 1998.
Distribution
Cossinia has a disjunct distribution across four geographically separated regions: the Mascarene Islands (C. pinnata, Réunion and Mauritius), central-eastern to southeastern Queensland in Australia (C. australiana), New Caledonia (C. trifoliata), and Fiji (C. pacifica). This scattered range across the southwestern Pacific and Indian Ocean reflects a classic island-relict pattern within the Sapindaceae.
Ecology
Species grow in rainforest settings, including seasonally drought-prone rainforests and associated non-fire-adapted vegetation types. Their restriction to closed-canopy forest and absence from fire-adapted communities is ecologically significant, given that fire disturbance is widespread across much of their range in Queensland and the Pacific.
Conservation
Two of the four species face elevated extinction risk. Cossinia australiana is listed as Endangered under both Australian national legislation and Queensland state law; its known habitats in central-eastern and southeastern Queensland have historically been subject to extensive native vegetation clearance, with ongoing threats recorded as of 2013. Cossinia trifoliata, endemic to New Caledonia, was assessed as Vulnerable by the IUCN in 1998.
