3 species & 2 hybrids in Australia
Mature fruits have a persistent star-shaped calyx. The genus Sonneratia L.f. (1782) belongs to the Sonneratiaceae Engl. & Gilg, a small tropical family of the order Myrtales with just two genera restricted to the Indo-West Pacific region. Sonneratia consist entirely of mangrove trees, while the other genus Duabanga Buch.-Ham.is made up of small evergreen rainforest shrubs from Indo-Malaya. Sonneratia are notable for their large showy flowers with numerous red or white stamens and their berry-shaped fruit seated on a persistent calyx with 6-8 erect pointed lobes. Fruits enclose a firm pulp imbedded with numerous small seeds that commonly germinate on exposed mud banks.
Sonneratia grow mostly along banks of tidal rivers, creeks and within sheltered bays of offshore islands and reef cays. In estuaries, they occupy distinct upriver ranges where: sibling species, S. caseolaris and S. lanceolata, occur in upstream reaches of river-dominated estuaries; S. alba occurs in downstream stands and offshore island embayments; and S. X gulngai and S. X urama, the two Australasian hybrids occur in small intermediate stands between the respective parents. Another species just north in New Guinea, S. ovata Backer, prefers a different habit, occurring at the high tide margin.
Derivation of Genus Name
Named for the French naturalist, Pierre Sonnerat (1748-1814), remembered for his explorations of New Guinea, Moluccas and China, including the first European description of lychee fruit.
Sonneratia occur throughout the Indo-West Pacific region from East Africa to China, through Asia and Indonesia, to New Guinea, the western Pacific and northern Australia. In Australia, there are three species and two hybrids. A third hybrid, S. alba X S. gulngai, is known only as a single tree in the McIvor River, north-eastern Australia.
Key to Australia's Sonneratia species
Three Sonneratia species and two widely-occurring hybrids are recognised in Australia’s mangroves across the northern coast from Western Australia, Northern Territory and Queensland. They are distinguished by colour of petals and stamens, calyx surface, shape of the calyx on mature fruit, plus the shape of leaves and leaf apices.