Adenanthos is a genus of approximately 33 species of shrubs native to Australia, belonging to the family Proteaceae in the order Proteales. It is the sole genus in Proteaceae in which solitary flowers are the norm — a trait that sets it apart from the clustered inflorescences typical of the family. Plants in the genus are variable in habit and leaf shape, ranging from low ground-covers to larger shrubs adapted to the nutrient-poor soils of Australian heathland.
The genus was first discovered in 1791 and formally described by the French botanist Jacques Labillardière in 1805. It is placed in the subfamily Proteoideae and is considered most closely related to several South African genera within that group. The type species is Adenanthos cuneatus, a low-spreading shrub of southwestern Western Australia.
Adenanthos is endemic to Australia, with its centre of diversity in the Southwest Australian Floristic Region — one of the world's 36 biodiversity hotspots. Thirty-one of the 33 species are confined to southwest Western Australia, particularly the kwongan heath of the Esperance Plains, where 17 species co-occur. The remaining species include Adenanthos macropodianus (Kangaroo Island glandflower), endemic to Kangaroo Island, and Adenanthos terminalis (yellow glandflower), which extends from South Australia into western Victoria. The plants are mainly pollinated by honeyeaters, and their flowers are adapted to bird visitation.
Etymology
The name Adenanthos derives from Greek, reflecting the glandular character of the flowers — aden (gland) and anthos (flower). The genus was formally named by Jacques Labillardière in 1805.
Distribution
Adenanthos is endemic to Australia, with 31 of its 33 species confined to southwest Western Australia, particularly the Esperance Plains kwongan heath. The two remaining species extend east: Adenanthos macropodianus is endemic to Kangaroo Island, and Adenanthos terminalis occurs on the Eyre Peninsula, Kangaroo Island, and into western Victoria. The genus is absent from the drier inland north of the Avon Wheatbelt region but penetrates further inland in the south, with A. argyreus reaching as far as Southern Cross.
Ecology
Adenanthos flowers are visited and pollinated primarily by honeyeaters. Recorded visitors include the eastern spinebill (Acanthorhynchus tenuirostris), little wattlebird (Anthochaera chrysoptera), New Holland honeyeater (Phylidonyris novaehollandiae), crescent honeyeater, tawny-crowned honeyeater, silvereye, and brown-headed honeyeater. Research suggests that bird visitation rates at a site correlate more strongly with the abundance of co-occurring Banksia sessilis than with the density of Adenanthos plants themselves.
