Together with the Platanaceae (plane trees), Nelumbonaceae (the sacred lotus) and in the recent APG IV system the Sabiaceae, they make up the order Proteales.

[citation needed] The genera of Proteaceae are highly varied, with Banksia in particular providing a striking example of adaptive radiation in plants.

[6] This variability makes it impossible to provide a simple, diagnostic identification key for the family, although individual genera may be easily identified.

In many genera, the most obvious feature is the large and often very showy inflorescences, consisting of many small flowers densely packed into a compact head or spike.

They are an adaptation to growth in poor, phosphorus-deficient soils, greatly increasing the plants' access to scarce water and nutrients by exuding carboxylates that mobilise previously unavailable phosphorus.

[8] However, this adaptation leaves them highly vulnerable to dieback caused by the Phytophthora cinnamomi water mould, and generally intolerant of fertilization.

Due to these specialized proteoid roots, the Proteaceae are one of few flowering plant families that do not form symbioses with arbuscular mycorrhizal fungi.

Pollination is carried out by bees, beetles, flies, moths, birds (honeyeaters, sunbirds, sugarbirds and hummingbirds) and mammals (rodents, small marsupials, elephant shrews and bats).

These trees accumulate fruits on their branches whose outer layers or protective structures (bracts) are highly lignified and resistant to fire.

[9] It is a good example of a Gondwanan family, with taxa occurring on virtually every land mass considered a remnant of the ancient supercontinent Gondwana, except Antarctica.

Cyanogenic glycosides, derived from tyrosine, are often present, as are proanthocyanidines (delphinidin and cyanidin), flavonols (kaempferol, quercetin and myricetin) and arbutin.

Many traditional cultures have used Proteaceae as sustenance, medicine, for curing animal hides, as a source of dyes, firewood and as wood for construction.

Aboriginal Australians eat the fruit of Persoonia, and the seeds of species from other genera, including Gevuina and Macadamia, form part of the diet of the indigenous peoples but are also sold throughout the world.

Traditional medicines can be obtained from infusions of the roots, bark, leaves, or flowers of many species that are used as topical applications for skin conditions or internally as tonics, aphrodisiacs, and galactogens to treat headaches, cough, dysentery, diarrhea, indigestion, stomach ulcers, and kidney disease.

Gevuina avellana (Chilean hazel) is also cultivated for its edible nuts, in Chile and New Zealand, and they are also used in the pharmaceutical industry for their humectant properties and as an ingredient in sunscreens.

[citation needed] It is also planted in the British Isles and on the Pacific coast of the United States for its tropical appearance and its ability to grow in cooler climates.

Some temperate climate species are cultivated more locally in Australia for their attractive appearance: Persoonia pinifolia (pine-leaved geebung) is valued for its vivid yellow flowers and grape-like fruit.

Adenanthos sericeus (woolly bush) is planted for its attractive soft leaves and its small red or orange flowers.

The Proteaceae are particularly susceptible to certain parasites, in particular the oomycete Phytophthora cinnamomi, which causes severe root rot in the plants that grow in Mediterranean climates.

The species of this family are particularly susceptible to the destruction or fragmentation of their habitat, fire, parasitic diseases, competition from introduced plants, soil degradation and other damage provoked by humans and their domesticated animals.

The fossil record of some areas, such as New Zealand and Tasmania, show a greater biodiversity for Proteaceae than currently exists, which supports the fact that the distribution of many taxa has changed drastically with the passage of time and that the family has suffered a general decline, including high levels of extinction during the Cenozoic.

[citation needed] First described by French botanist Antoine Laurent de Jussieu, the family Proteaceae is a fairly large one, with around 80 genera, but less than 2,000 species.