Acacia

Acacia (/əˈkeɪʃə/ or /əˈkeɪsiə/) is a monophyletic genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or shittah trees. The genus name is derived via Latin from ancient Greek ακακία (akakia). It was the name used by Theophrastus and Dioscorides to denote thorn trees, the word root being ἀκίς (akis) or ἀκή (akḗ), meaning "thorn" and "point" respectively. Before discovery of the New World, Europeans in the Mediterranean region were familiar with several species of Acacia, which they knew as sources of medicine, and had names for them that they inherited from the Greeks and Romans.

The wide-ranging genus occurs in a variety of open, tropical to subtropical habitats, and is locally dominant. In parts of Africa, Acacias are shaped progressively by grazing animals of increasing size and height, such as gazelle, gerenuk and giraffe. The genus in Africa has thus developed thorns in defence against such herbivory. They belong to the subfamily Mimosoideae, the major clades of which may have formed in response to drying trends and fire regimes that accompanied increased seasonality during the late Oligocene to early Miocene (∼25 mya). Pedley (1978), following Vassal (1972), viewed Acacia as comprising three large subgenera, but subsequently (1986) raised the rank of these groups to genera Acacia, Senegalia (s.l.) and Racosperma, which was underpinned by later genetic studies. The International Code of Nomenclature provides that under the rules, if Acacia is dismantled, then the name Acacia follows the type.