Acacia mearnsii

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Black wattle
Acacia mearnsii blossoms.jpg
Acacia mearnsii on Maui
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Subfamily: Caesalpinioideae
Clade: Mimosoid clade
Genus: Acacia
Species:
A. mearnsii
Binomial name
Acacia mearnsii
Acacia mearnsiiDistMap582.png
Occurrence data from AVH
Synonyms [1]
  • Racosperma mearnsii(De Wild.) Pedley

Acacia mearnsii, commonly known as black wattle, late black wattle or green wattle, [2] 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 leaves and spherical heads of fragrant pale yellow or cream-coloured flowers followed by black to reddish brown pods. In some other parts of the world, it is regarded as an invasive species.

Contents

Description

Acacis mearnsii is a spreading shrub or erect tree that typically grows to a height of 10 m (33 ft) and has smooth bark, sometimes corrugated at the base of old specimens. The leaves are bipinnate with 7 to 31 pairs of pinnae, each with 25 to 78 pairs of pinnules. There is a spherical gland up to 8 mm (0.31 in) below the lowest pair of pinnae. The scented flowers are arranged in spherical heads of twenty to forty and are pale yellow or cream-coloured, the heads on hairy peduncles 2–8 mm (0.079–0.315 in) long. Flowering mainly occurs from October to December and black to reddish-brown pods, 30–150 mm (1.2–5.9 in) long and 4.5–8 mm (0.18–0.31 in) wide develop from October to February. [2] [3] [4]

Taxonomy

Belgian naturalist Émile Auguste Joseph De Wildeman described the black wattle in 1925 in his book Plantae Bequaertianae. [5] The species is named after American naturalist Edgar Alexander Mearns, who collected the type from a cultivated specimen in East Africa. [6] Along with other bipinnate wattles, it is classified in the section Botrycephalae within the subgenus Phyllodineae in the genus Acacia. An analysis of genomic and chloroplast DNA along with morphological characters found that the section is polyphyletic, though the close relationships of many species were unable to be resolved. Acacia mearnsii appears to be most closely related to A. dealbata , A. nanodealbata and A. baileyana . [7]

Distribution and habitat

A. mearnsii is native to south-eastern Australia and Tasmania, but has been introduced to North America, South America, Asia, Europe, Pacific and Indian Ocean islands, Africa, and New Zealand. [8] [9] [10] [11] [12] In these areas it is often used as a commercial source of tannin or a source of firewood for local communities.

In some regions, introduced plants of this species are considered a weed. This is because they threaten native habitats by competing with indigenous vegetation, replacing grass communities, reducing native biodiversity and increasing water loss from riparian zones. In Africa, A. mearnsii competes with local vegetation for nitrogen and water resources, which are particularly scarce in certain regions, endangering the livelihoods of millions of people. [13]

In its native range A. mearnsii is a tree of tall woodland and forests in subtropical and warm temperate regions. In Africa the species grows in disturbed areas, range/grasslands, riparian zones, urban areas, water courses, and mesic habitats at an altitude of between 600-1700m. In Africa it grows in a range of climates including warm temperate dry climates and moist tropical climates. A. mearnsii is reported to tolerate an annual precipitation of between 66 to 228 centimetres (26 to 90 in), an annual mean temperature of 14.7 to 27.8 °C (58.5 to 82.0 °F), and a pH of 5.0 – 7.2. [14] A. mearnsii does not grow well on very dry and poor soils. [15]

Ecology in Australia

A. mearnsii plays an important role in the ecosystem in its native Australia. As a pioneer plant it quickly binds the erosion-prone soil following the bushfires that are common in its Australian habitats. Like other leguminous plants, it fixes the atmospheric nitrogen in the soil. Other woodland species can rapidly use these increased nitrogen levels provided by the nodules of bacteria present in their expansive root systems. Hence they play a critical part in the natural regeneration of Australian bushland after fires.

Acacia mearnsii seed pods Starr 050816-7454 Acacia mearnsii.jpg
Acacia mearnsii seed pods

Mycorrhizal fungi attach to the roots to produce food for marsupial animals, and these animals in turn disperse the spores in their droppings to perpetuates the symbiotic relationship between wattle's roots and the mycorrhizal fungi.

The cracks and crevices in the wattle's bark are home for many insects and invertebrates. The rare Tasmanian hairstreak butterfly lays her eggs in these cracks, which hatch to produce caterpillar larva attended by ants ( Iridomyrmex sp.) that feed off the sweet exudates from the larva.[ citation needed ]A. mearnsii is used similarly as a larval host plant and food source by the imperial hairstreak, Jalmenus evagoras . [20]

The tree is home to various grubs, such as wood moths, which provide a food source to the Australian black cockatoos, who strip the bark for access to these borers.

During winter insects, birds and marsupials are hosted by the black wattle with the aid of their supplies of nectar in their leaf axials. These creatures provide an important predatory role to deal with tree dieback caused by scarab beetles and pasture pests.

Black wattles, along with gums, native box and native hop form the framework vegetation on so-called "hill-topping" sites. They are often isolated remnant pockets of native vegetation amongst a lower sea of exotic pasture. These "hill-topping" sites are critical habitat for male butterflies to attract females for mating, which then lay their eggs under the wattle's bark elsewhere but still within close proximity. It's the only acceptable mating site in the area for these butterflies.

Black wattle flowers provide very nitrogen rich pollen with no nectar. They attract pollen-feeding birds such as wattlebirds, yellow-throated honeyeaters and New Holland honeyeaters. The protein-rich nectar in the leaf axials is very sustaining for nurturing the growth of juvenile nestlings and young invertebrates, e.g. ants.

Ants harvest the seed, attracted by the fleshy, oil rich elaiosome (or seed stalk), which they bury and store in widely dispersed locations. These seeds are buried ready for germinating with the next soaking rains. However, a "wattle seed-eating insect" which enjoys liquid meals using its proboscis-like injector to pierce the testa and suck out the embryo, often reduces the seed's viability. [21]

Status as an invasive species

In some parts of the world, A. mearnsii is considered to be an invasive species. Its invasiveness is due to its production of large numbers of seeds each year and to its large crown that shades other species. [22]

In South Africa it is listed as a Category 2 invader in the National Environmental Biodiversity Management Act. This means a permit is required to handle a species and ensure it does not spread beyond the area of the permit. [23]

Uses

The Ngunnawal people of the Australian Capital Territory use the gum as food and to make cement (when mixed with ash), and to ensure a supply of sap, the bark was cut in the autumn. [24] The bark was also used to make coarse rope and string, and used to be infused in water to make a medicine for indigestion. [24]

Reproduction

A. mearnsii produces copious numbers of small seeds that are not dispersed actively. The species may resprout from basal shoots following a fire. [8] It also generates numerous suckers that result in thickets consisting of clones. [8] Seeds may remain viable for up to 50 years. [25]

Chemistry

Leuco-fisetinidin, a flavan-3,4-diol (leucoanthocyanidin) and a monomer of the condensed tannins called profisetinidins, can be extracted from the heartwood of A. mearnsii. [26]

Related Research Articles

<i>Acacia sensu lato</i> Genus of legumes

Acacia s.l., known commonly as mimosa, acacia, thorntree or wattle, is a polyphyletic genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae. It was described by the Swedish botanist Carl Linnaeus in 1773 based on the African species Acacia nilotica. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. All species are pod-bearing, with sap and leaves often bearing large amounts of tannins and condensed tannins that historically found use as pharmaceuticals and preservatives.

<i>Robinia pseudoacacia</i> Species of tree native to North America

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 States, but it has been widely planted and naturalized elsewhere in temperate North America, Europe, Southern Africa and Asia and is considered an invasive species in some areas. Another common name is false acacia, a literal translation of the specific name.

<i>Acacia pycnantha</i> Golden wattle of southeastern Australia

Acacia pycnantha, most commonly known as the golden wattle, is a tree of the family Fabaceae native to southeastern Australia. It grows to a height of 8 m (26 ft) and has phyllodes instead of true leaves. Sickle-shaped, these are between 9 and 15 cm long, and 1–3.5 cm wide. The profuse fragrant, golden flowers appear in late winter and spring, followed by long seed pods. Plants are cross-pollinated by several species of honeyeater and thornbill, which visit nectaries on the phyllodes and brush against flowers, transferring pollen between them. An understorey plant in eucalyptus forest, it is found from southern New South Wales and the Australian Capital Territory, through Victoria and into southeastern South Australia.

<i>Acacia saligna</i> Species of plant in the family Fabaceae native to Australia

Acacia saligna, commonly known by various names including coojong, golden wreath wattle, orange wattle, blue-leafed wattle, Western Australian golden wattle, and, in Africa, Port Jackson willow, is a small tree in the family Fabaceae. Native to Australia, it is widely distributed throughout the south west corner of Western Australia, extending north as far as the Murchison River, and east to Israelite Bay. The Noongar peoples know the tree as Cujong.

<i>Acacia</i> Genus of plants

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 Neo-Latin, borrowed from the Greek ἀκακία, 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 ἀκακία from Dioscorides as the origin of the Latin name.

<span class="mw-page-title-main">Wattleseed</span> Acacia seeds eaten by Aboriginal Australians

Wattleseeds are the edible seeds from any of 120 species of Australian Acacia that were traditionally used as food by Aboriginal Australians, and eaten either green or dried to make a type of bush bread. Acacia murrayana and A. victoriae have been studied as candidates for commercial production.

<i>Acacia implexa</i> Species of plant

Acacia implexa, commonly known as lightwood or hickory wattle, is a fast-growing Australian tree, the timber of which is used for furniture making. The wood is prized for its finish and strength. The foliage was used to make pulp and dye cloth.

<i>Acacia dealbata</i> Species of flowering plant

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 widely introduced in Mediterranean, warm temperate, and highland tropical landscapes.

<span class="mw-page-title-main">Black wattle</span> Index of plants with the same common name

Black wattle is the common name for a number of species of trees that are native to Australia, as listed below:

<i>Acacia parramattensis</i> Species of legume

Acacia parramattensis, commonly known as Parramatta wattle, is a tree of the family Fabaceae native to the Blue Mountains and surrounding regions of New South Wales. It is a tall shrub or tree to about 15 m (49 ft) in height with phyllodes instead of true leaves. These are finely divided bipinnate. The yellow flowers appear over summer. It generally grows in woodland or dry sclerophyll forest on alluvial or shale-based soils, generally with some clay content.

<i>Acacia salicina</i> Species of plant

Acacia salicina is a thornless species of Acacia tree native to Australia.

<i>Acacia decurrens</i> Species of legume

Acacia decurrens, commonly known as black wattle or early green wattle, is a perennial tree or shrub native to eastern New South Wales, including Sydney, the Greater Blue Mountains Area, the Hunter Region, and south west to the Australian Capital Territory. It grows to a height of 2–15 m (7–50 ft) and it flowers from July to September.

<i>Acacia falcata</i> Species of legume

Acacia falcata, commonly known as sickle wattle and by other vernacular names including sally, is a perennial shrub or tree native to eastern Australia, which reaches five metres in height and has cream flowers in early winter. It gets its common and scientific name for its sickle-shaped leaves. Hardy and adaptable to cultivation, it is used in regeneration of bushland.

<i>Vachellia</i> Genus of legumes

Vachellia is a genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or acacias. It belongs to the subfamily Mimosoideae. Its species were considered members of genus Acacia until 2009. Vachellia can be distinguished from other acacias by its capitate inflorescences and spinescent stipules. Before discovery of the New World, Europeans in the Mediterranean region were familiar with several species of Vachellia, which they knew as sources of medicine, and had names for them that they inherited from the Greeks and Romans.

<i>Acacia flavescens</i> Species of legume

Acacia flavescens, also known as the red wattle, yellow wattle or primrose ball wattle, is a tree in the genus Acacia native to eastern Australia.

<i>Acacia pubescens</i> Species of legume

Acacia pubescens, also known as the downy wattle, is a species of wattle found in the Sydney Basin in eastern New South Wales. The downy wattle is classified as vulnerable; much of its habitat has vanished with the growth of the city of Sydney.

<i>Acacia cana</i> Species of legume

Acacia cana, or commonly named as boree or the cabbage-tree wattle or broad-leaved nealie, is part of the family Fabaceae and sub-family Mimosoideae. It is a dense shrub- tree that can grow to 6 metres (20 ft) high and is a perennial plant meaning it has long life span and doesn’t necessary produce a high amount of seed. The cabbage-tree wattle heavily flowers from August till October and relies on animals and insects for pollination and dispersal of seeds. This least concern acacia species is found in the western plains of New South Wales and Central Queensland the habitats of these areas are found to be sandy soils and gibber plains.

<i>Acacia iteaphylla</i> Species of plant

Acacia iteaphylla, commonly known as Flinders Range wattle, Port Lincoln wattle, winter wattle and willow-leaved wattle, is a shrub belonging to the genus Acacia and the subgenus Phyllodineae that is endemic to South Australia.

<i>Acacia shirleyi</i> Species of legume

Acacia shirleyi, known colloquially as lancewood, is a species of Acacia native to Queensland and the Northern Territory in Australia. It grows as a tree to 15 metres (49 ft) high, with dark grey or black stringy bark and blue-grey foliage. The yellow flowers appear from March to July. It grows in dry scrub, open forest or mixed savannah woodland. Indigenous people used the wood as fuel and to make hunting spears. Cattle can eat the foliage as fodder.

<i>Acacia carneorum</i> Species of plant

Acacia carneorum, also referred to as purple-wood wattle, needle wattle, dead finish or by its former scientific name, Acacia carnei, is a plant species in the genus Acacia.

References

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