Pisonia is a genus of tropical and subtropical flowering plants in the family Nyctaginaceae (the four o'clock family), within the order Caryophyllales. Approximately 27 species are accepted, distributed across pantropical regions including the Caribbean, Central and South America, the Galápagos Islands, and the tropical Indo-Pacific.
The genus is perhaps best known for its birdcatcher species — trees and shrubs whose seeds are coated in an intensely sticky mucilage. This adaptation gives several species common names such as birdcatcher tree, catchbirdtree, or birdlime tree. The sticky seeds are thought to facilitate long-distance dispersal across ocean island chains by adhering to the feathers of seabirds, which carry them between islands. On coral-sand islands, seeds that fall with entangled birds also enrich the otherwise nutrient-poor coralline soil as the bird decomposes, providing a localised fertilisation effect at the base of the tree. Notable birdcatcher species include Pisonia brunoniana of Australasia and Polynesia, and the widespread Indo-Pacific P. umbellifera. Pisonia aculeata — an armed, scrambling shrub — has a pantropical distribution, while P. grandis (grand devil's-claws) is widespread across the Indo-Pacific and P. floribunda (pega pega) is native to the Galápagos Islands.
The genus was named in honour of the Dutch physician and naturalist Willem Piso (1611–1678), a pioneering figure in the natural history of Brazil.
Etymology
The genus Pisonia was named by Carl Linnaeus in honour of Willem Piso (1611–1678), a Dutch physician and naturalist who was among the first Europeans to document the natural history of Brazil. The common names "birdcatcher tree," "catchbirdtree," and "birdlime tree" reflect the genus's most striking trait: seeds covered in a tenacious sticky mucilage capable of adhering to birds.
Distribution
Pisonia species occur throughout pantropical and subtropical regions. The genus has a broad Caribbean presence (including Puerto Rico and Cuba), extends through Central America to South America, and includes the Galápagos Islands (P. floribunda). In the Indo-Pacific, P. umbellifera and P. grandis range widely across oceanic islands. P. brunoniana is native to Australasia and Polynesia. P. aculeata has become nearly cosmopolitan in the tropics.
Ecology
Several Pisonia species occupy critical ecological roles on low-lying coral and volcanic islands, where they form dense tree colonies on seabird nesting grounds. The sticky, mucilage-coated seeds of island species (notably P. brunoniana and P. umbellifera) are an adaptation for dispersal by seabirds: seeds adhere to feathers and are carried between islands across open ocean. Where seabirds nesting under Pisonia trees become heavily encumbered by seeds and die, their bodies locally enrich nitrogen-poor coralline sands, effectively fertilising the soil around the parent tree's root zone. This creates a feedback loop between Pisonia forest structure and seabird colony productivity on atolls and small islands.
