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''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus name is
New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy a ...
, borrowed from the Greek (), a term used by Dioscorides for a preparation extracted from the leaves and fruit pods of '' Vachellia nilotica'', the original type of the genus. In his ''Pinax'' (1623), Gaspard Bauhin mentioned the Greek from Dioscorides as the origin of the Latin name. In the early 2000s it had become evident that the genus as it stood was not monophyletic and that several divergent lineages needed to be placed in separate genera. It turned out that one lineage comprising over 900 species mainly native to Australia, New Guinea, and Indonesia was not closely related to the much smaller group of African lineage that contained ''A. nilotica''—the type species. This meant that the Australasian lineage (by far the most prolific in number of species) would need to be renamed. Botanist Leslie Pedley named this group ''Racosperma'', which received little acclaim in the botanical community. Australian botanists proposed a less disruptive solution setting a different type species for ''Acacia'' ('' A. penninervis'') and allowing this largest number of species to remain in ''Acacia'', resulting in the two Pan-Tropical lineages being renamed '' Vachellia'' and '' Senegalia'', and the two endemic American lineages renamed ''
Acaciella ''Acaciella'' is a Neotropical genus of flowering plants in the legume family, Fabaceae, and its subfamily Mimosoideae. Its centre of diversity is along the Mexican Pacific coast. They are unarmed, have no extrafloral nectaries and the polyads ...
'' and ''
Mariosousa ''Mariosousa'' is a genus of 13 species of flowering plants in the family Fabaceae. It belongs to the mimosoid clade of the subfamily Caesalpinioideae. Members of this genus were formerly considered to belong to the genus ''Acacia ''Acacia ...
''. Although many botanists still disagreed that this was necessary, this solution was eventually officially adopted at the Melbourne International Botanical Congress in 2011. Acacia remains a widely used common name across genera. A number of species have been introduced to various parts of the world, and two million hectares of commercial plantations have been established. The heterogeneous group varies considerably in habit, from mat-like subshrubs to canopy trees in a forest.


Description

Several species in the genus bear vertically oriented phyllodes, which are green, broadened leaf petioles that function like leaf blades, an adaptation to hot climates and droughts. Some phyllodinous species have a colourful aril on the seed. A few species have cladodes rather than leaves.


Taxonomy

The genus was first validly named in 1754 by Philip Miller. In 1913
Nathaniel Lord Britton Nathaniel Lord Britton (January 15, 1859 – June 25, 1934) was an American botanist and taxonomist who co-founded the New York Botanical Garden in the Bronx, New York. Early life Britton was born in New Dorp in Staten Island, New York to Jaspe ...
and
Addison Brown Addison C. Brown (February 21, 1830 – April 9, 1913) was a United States district judge of the United States District Court for the Southern District of New York, a botanist, and a serious amateur astronomer. Early life, education and career A ...
selected ''Mimosa scorpioides'' (≡ ''Acacia scorpioides'' () = ''
Acacia nilotica ''Vachellia nilotica'', more commonly known as ''Acacia nilotica'', and by the vernacular names of gum arabic tree, babul, thorn mimosa, Egyptian acacia or thorny acacia, is a flowering tree in the family Fabaceae. It is native to Africa, the M ...
'' () ), a species from Africa, as the
lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...
of the name. The genus as recognized in 1986 contained 1352 species. That year however, Pedley published a paper in which he questioned the monophyletic nature of the genus, and proposed a split into three genera: ''Acacia''
sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...
(161 species), ''Senegalia'' (231 species) and ''Racosperma'' (960 species), the last name first proposed in 1829 by
Carl Friedrich Philipp von Martius Carl Friedrich Philipp (Karl Friedrich Philipp) von Martius (17 April 1794 – 13 December 1868) was a German botanist and explorer. Life Martius was born at Erlangen, the son of Prof Ernst Wilhelm Martius, court apothecary. He graduated PhD f ...
as the name of a section in ''Acacia'', but raised to generic rank in 1835. In 2003, Pedley published a paper with 834 new combinations in ''Racosperma'' for species, most of which were formerly placed in ''Acacia''. All but 10 of these species are native to
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...
, where it constitutes the largest plant genus. In 2003, Anthony Orchard and Bruce Maslin filed a proposal to conserve the name ''Acacia'' with a different type in order to retain the Australasian group of species in the genus ''Acacia''. Following a controversial decision to choose a new type for ''Acacia'' in 2005, the Australian component of ''Acacia s.l.'' now retains the name ''Acacia''. At the 2011
International Botanical Congress International Botanical Congress (IBC) is an international meeting of botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the location rotati ...
held in Melbourne, the decision to use the name ''Acacia'', rather than the proposed ''Racosperma'' for this genus, was upheld. Other '' Acacia s.l.'' taxa continue to be called ''Acacia'' by those who choose to consider the entire group as one genus. Australian species of the genus ''
Paraserianthes ''Paraserianthes'' is a genus of flowering plants in the family Fabaceae. It belongs to the mimosoid clade of the subfamily Caesalpinioideae. Taxonomy ''Paraserianthes'' includes only one species: * '' Paraserianthes lophantha'' (Willd.) I.C.Ni ...
'' ''
s.l. SL may refer to: Arts and entertainment * SL (rapper), a rapper from London * ''Second Life'', a multi-user 3D virtual world * Sensei's Library, an Internet site dedicated to the game of Go * Subdominant leittonwechselklänge * Leica SL, a mirr ...
'' are deemed its closest relatives, particularly '' P. lophantha''. The nearest relatives of ''Acacia'' and ''Paraserianthes s.l.'' in turn include the Australian and South East Asian genera ''
Archidendron ''Archidendron'' is a genus of flowering plants in the pea family, Fabaceae. Image:Archidendron lucyii foliage.jpg, ''Archidendron lucyii'' leaves Image:Pithecellobium jiringa.JPG, ''Archidendron pauciflorum'' fruits Image:Archidendron lucyii f ...
'', ''
Archidendropsis ''Archidendropsis'' is a genus of flowering plants in the family Fabaceae The Fabaceae or Leguminosae,Pararchidendron ''Pararchidendron'' is a genus of flowering plants in the family Fabaceae. It belongs to the mimosoid clade of the subfamily Caesalpinioideae Caesalpinioideae is a botanical name at the rank of subfamily, placed in the large family Fabaceae o ...
'' and '' Wallaceodendron'', all of the tribe
Ingeae The Mimosoideae are a traditional subfamily of trees, herbs, lianas, and shrubs in the pea family (Fabaceae) that mostly grow in tropical and subtropical climates. They are typically characterized by having radially symmetric flowers, with petals ...
.


Etymology

The origin of "
wattle Wattle or wattles may refer to: Plants *''Acacia sensu lato'', polyphyletic genus of plants commonly known as wattle, especially in Australia and South Africa **''Acacia'', large genus of shrubs and trees, native to Australasia ** Black wattle, ...
" may be an Old Teutonic word meaning "to weave". From around 700 CE, ' was used in Old English to refer to the interwoven branches and sticks which formed fences, walls and roofs. Since about 1810 it refers to the Australian legumes that provide these branches.


Species

One species of ''Acacia'' (''
sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...
'') is native to Madagascar, one to
Reunion island Reunion may refer to: * Class reunion * Family reunion Reunion, Réunion, Re-union, Reunions or The Reunion may also refer to: Places * Réunion, a French overseas department and island in the Indian Ocean * Reunion, Commerce City, Colorado, ...
, 12 to
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, and the remaining species (over 900) are native to
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...
and the Pacific Islands. These species were all given combinations by Pedley when he erected the genus ''Racosperma'', hence ''
Acacia pulchella ''Acacia pulchella'', commonly known as prickly moses or western prickly moses, is a shrub in the family Fabaceae. Endemic to Western Australia, it is one of the most common shrubs of the bushland around Perth and in the Darling Range. Descri ...
'', for example, became ''
Racosperma pulchellum ''Acacia pulchella'', commonly known as prickly moses or western prickly moses, is a shrub in the family Fabaceae. Endemic to Western Australia, it is one of the most common shrubs of the bushland around Perth and in the Darling Range. Descri ...
''. However, these were not upheld with the retypification of ''Acacia''.


Phylogeny

Acacias in Australia probably evolved their fire resistance about 20 million years ago when fossilised charcoal deposits show a large increase, indicating that fire was a factor even then. With no major mountain ranges or rivers to prevent their spread, the wattles began to spread all over the continent as it dried and fires became more common. They began to form dry, open forests with species of the genera ''
Allocasuarina ''Allocasuarina'' is a genus of trees in the flowering plant family Casuarinaceae. They are endemic to Australia, occurring primarily in the south. Like the closely related genus ''Casuarina'', they are commonly called sheoaks or she-oaks. ...
'', '' Eucalyptus'' and ''
Callitris ''Callitris'' is a genus of coniferous trees in the Cupressaceae (cypress family). There are 16 recognized species in the genus, of which 13 are native to Australia and the other three (''C. neocaledonica, C. sulcata'' and ''C.  ...
'' (cypress-pines). The southernmost species in the genus are ''
Acacia dealbata ''Acacia dealbata'', the silver wattle, blue wattle or mimosa, is a species of flowering plant in the legume family Fabaceae, native to southeastern Australia in New South Wales, Victoria, Tasmania, and the Australian Capital Territory, and widel ...
'' (silver wattle), ''
Acacia longifolia ''Acacia longifolia'' is a species of ''Acacia'' native to southeastern Australia, from the extreme southeast of Queensland, eastern New South Wales, eastern and southern Victoria, and southeastern South Australia. Common names for it include lo ...
'' (coast wattle or Sydney golden wattle), ''
Acacia mearnsii ''Acacia mearnsii'', commonly known as black wattle, late black wattle or green wattle, is a species of flowering plant in the family Fabaceae and is endemic to south-eastern Australia. It is usually an erect tree with smooth bark, bipinnate lea ...
'' (black wattle), and ''
Acacia melanoxylon ''Acacia melanoxylon'', commonly known as the Australian blackwood, is an ''Acacia'' species native in South eastern Australia. The species is also known as Blackwood, hickory, mudgerabah, Tasmanian blackwood, or blackwood acacia. The tree belo ...
'' (blackwood), reaching 43°30' S in Tasmania, Australia.


Fossil record

An ''Acacia''-like long fossil
seed pod This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnify ...
has been described from the Eocene of the
Paris Basin The Paris Basin is one of the major geological regions of France. It developed since the Triassic over remnant uplands of the Variscan orogeny (Hercynian orogeny). The sedimentary basin, no longer a single drainage basin, is a large sag in the cr ...
. ''Acacia''-like fossil pods under the name ''Leguminocarpon'' are known from late Oligocene
deposits A deposit account is a bank account maintained by a financial institution in which a customer can deposit and withdraw money. Deposit accounts can be savings accounts, current accounts or any of several other types of accounts explained below. ...
at different sites in Hungary. Seed pod
fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...
of †''Acacia parschlugiana'' and †''Acacia cyclosperma'' are known from
Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...
deposits in Switzerland. †''Acacia colchica'' has been described from the Miocene of West
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...
. Pliocene fossil pollen of an ''Acacia'' sp. has been described from West
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...
(including
Abkhazia Abkhazia, ka, აფხაზეთი, tr, , xmf, აბჟუა, abzhua, or ( or ), officially the Republic of Abkhazia, is a partially recognised state in the South Caucasus, recognised by most countries as part of Georgia, which ...
). Oldest records of fossil ''Acacia'' pollen in Australia are from the late
Oligocene epoch The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
, 25 million years ago.


Distribution and habitat

They are present in all terrestrial habitats, including alpine settings, rainforests, woodlands, grasslands, coastal dunes and deserts. In drier woodlands or forests they are an important component of the understory. Elsewhere they may be dominant, as in the
Brigalow Belt The Brigalow Belt is a wide band of acacia-wooded grassland that runs between tropical rainforest of the coast and the semi-arid interior of Queensland, Australia. The Interim Biogeographic Regionalisation for Australia (IBRA) divides the Br ...
, Myall woodlands and the eremaean Mulga woodlands. In Australia, ''Acacia'' forest is the second most common forest type after
eucalypt Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera (of the tribe Eucalypteae) found across Australasia: ''Eucalyptus'', ''Corymbia'', ''Angophora'', '' Stockwellia'', '' Allosy ...
forest, covering or 8% of total forest area. ''Acacia'' is also the nation's largest genus of flowering plants with almost 1,000 species found.


Ecology

Acacia is a common food source and host plant for butterflies of the genus ''
Jalmenus Jalmenus is a genus of butterflies in the family Lycaenidae.The genus is endemic to Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island ...
.'' The imperial hairstreak, ''
Jalmenus evagoras ''Jalmenus evagoras,'' the imperial hairstreak, imperial blue, or common imperial blue, is a small, metallic blue butterfly of the family Lycaenidae. It is commonly found in eastern coastal regions of Australia. This species is notable for its ...
,'' feeds on at least 25 acacia species. Many reptiles feed on the sap as well, such as the native house gecko in Australia.


Toxicity

Some species of acacia contain psychoactive alkaloids, and some contain
potassium fluoroacetate Sodium fluoroacetate is an organofluorine chemical compound with the formula FCH2CO2Na. This colourless salt has a taste similar to that of sodium chloride and is used as a rodenticide. History and production The effectiveness of sodium fluoro ...
, a rodent poison.


Uses

The seed pods, flowers, and young leaves are generally edible either raw or cooked.
Aboriginal Australians Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait Island ...
have traditionally harvested the seeds of some species, to be ground into flour and eaten as a paste or baked into a cake. The seeds contain as much as 25% more protein than common cereals, and they store well for long periods due to the hard seed coats. In addition to utilizing the edible seed and gum, the people employed the timber for implements, weapons, fuel and musical instruments. A number of species, most notably '' A. mangium'' (hickory wattle), '' A. mearnsii'' (black wattle) and '' A. saligna'' (coojong), are economically important and are widely planted globally for wood products,
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...
, firewood and fodder. ''A. melanoxylon'' (blackwood) and ''A. aneura'' (mulga) supply some of the most attractive timbers in the genus. Black wattle bark supported the tanning industries of several countries, and may supply tannins for production of waterproof
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s. Wattle bark collected in Australia in the 19th century was exported to Europe where it was used in the tanning process. One ton of wattle or mimosa bark contained about of pure tannin. In ancient Egypt, an ointment made from the ground leaves of an Acacia (sensu lato) was used to treat
hemorrhoid Hemorrhoids (or haemorrhoids), also known as piles, are vascular structures in the anal canal. In their normal state, they are cushions that help with stool control. They become a disease when swollen or inflamed; the unqualified term ''he ...
s. The hardened
sap Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from latex, resin, or cell sap; it is a separ ...
of various species of the acacia tree (sensu lato) are known as
acacia gum Gum arabic, also known as gum sudani, acacia gum, Arabic gum, gum acacia, acacia, Senegal gum, Indian gum, and by other names, is a natural gum originally consisting of the hardened sap of two species of the ''Acacia'' tree, ''Senegalia sen ...
. Acacia gum is used as an emulsifier in food, a binder for watercolour painting, an additive to
ceramic glazes Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a pottery body through firing. Glaze can serve to color, decorate or waterproof an item. Glazing renders earthenware vessels suitable for holding ...
, a binding in gum bichromate photography, a protective layer in the lithographic processes and as a binder to bind together fireworks. "Acacia honey" is not collected from plants in the acacia family, but rather from ''
Robinia pseudoacacia ''Robinia pseudoacacia'', commonly known in its native territory as black locust, is a medium-sized hardwood deciduous tree, belonging to the tribe Robinieae of the legume family Fabaceae. It is endemic to a few small areas of the United Sta ...
'', known as black locust in North America. Honey collected from ''
Caragana arborescens ''Caragana arborescens'', the Siberian peashrub, Siberian pea-tree, or caragana, is a species of legume native to Siberia and parts of China (Heilongjiang, Xinjiang) and neighboring Mongolia and Kazakhstan. It was taken to the United States by ...
'' is sometimes also called (yellow) acacia honey. (See also
Monofloral honey Monofloral honey is a type of honey which has a distinctive flavor or other attribute due to its being predominantly from the nectar of a single plant species. It is stored and labeled separately so as to command a premium price. While there may ...
.)


Cultivation

Some species of acacia – notably ''A. baileyana'', '' A. dealbata'' and '' A. pravissima'' – are cultivated as ornamental garden plants. The 1889 publication ''Useful Native Plants of Australia'' describes various uses for eating.


In culture

Acacia is mentioned in an ancient Egyptian proverb referred to by
Amenhotep II Amenhotep II (sometimes called ''Amenophis II'' and meaning ''Amun is Satisfied'') was the seventh pharaoh of the Eighteenth Dynasty of Egypt. Amenhotep inherited a vast kingdom from his father Thutmose III, and held it by means of a few militar ...
: "If you lack a gold battle-axe inlaid with bronze, a heavy club of acacia wood will do."Erik Hornung 'The Pharaoh' in Sergio Donadoni, The Egyptians, The University of Chicago Press, 1997. p. 291 Acacia (sensu lato) is repeatedly mentioned in the Book of Exodus, perhaps referring to ''
Vachellia tortilis ''Vachellia tortilis'', widely known as ''Acacia tortilis'' but now attributed to the genus '' Vachellia'', is the umbrella thorn acacia, also known as ''umbrella thorn'' and Israeli babool, a medium to large canopied tree native to most of Afr ...
'' (previously known as ''Acacia raddiana''), in regards to the construction of the Tabernacle. In
Exodus Exodus or the Exodus may refer to: Religion * Book of Exodus, second book of the Hebrew Torah and the Christian Bible * The Exodus, the biblical story of the migration of the ancient Israelites from Egypt into Canaan Historical events * E ...
25:10, acacia wood is mentioned as the construction material for the
Ark of the Covenant The Ark of the Covenant,; Ge'ez: also known as the Ark of the Testimony or the Ark of God, is an alleged artifact believed to be the most sacred relic of the Israelites, which is described as a wooden chest, covered in pure gold, with an el ...
.


References

* Pedley, L. (2002). "A conspectus of ''Acacia'' subgen. ''Acacia'' in Australia". ''Austrobaileya'' 6(2): 177–186. * Pedley, L. (2003). A synopsis of ''Racosperma'' C.Mart". ''Austrobaileya'' 6(3): 445–496.


External links


WATTLE Acacias of Australia Lucid Web Player (multi-access key for identifying Australian Acacias)
{{Authority control Fabaceae genera Mimosoids