Acacia Mill.
Traditionally, this genus was composed of some 1,500 species worldwide, therefore considered one of the most diversified in the family. However, current phylogeny data obtained from molecular markers have recognised several lineages, proposing a new circumscription of the genus, with the recognition of 5 independent genera: Acacia Mill., Senegalia Raf., Vachellia Wight & Arn., Mariosousa Seigler & Ebinger y Acaciella Britton & Rose. Such segregation, established in 2011 after the resolution adopted at the International Botanical Congress in Melbourne (from a proposal made at the Seventeenth International Botanical Congress held in Vienna in 2005), is based on a new typification of the genus, since the type species Acacia scorpioides (L.) W.Wight [A. nilotica (L.) Willd. ex Del.], belonging to a minority lineage, has been replaced by a new type (A. penninervis Sieber ex DC.), in order to maintain maximum nomenclature stability. Thus, the genus Acacia continues to include the largest number of species (c. 1,075), most of them confined to Australia (plus a dozen Asian species and a couple of species in Madagascar), while the rest of the species are distributed among the other mentioned genera.
In North Africa all species of the genus are non native species and are cultivated for their wood, for rubber and tannin production, as dunes fixers, for their ornamental or forestry value, etc., some species may appear as adventitious or even locally naturalised or in process of becoming naturalised.
This project aims to recognise the value of the biodiversity of North Africa, while pointing out the need to curb the spread of introduced species, especially invasives, due to the numerous examples of serious disturbances caused by these species to the natural ecosystems and local economic systems. Although we will continue to insist that there are many North African native species that perform similar or better functions than the introduced species, we hereby present an identification key of the most used introduced Acacias, to facilitate their identification, for example, in programmes aimed at the eradication and replacement of introduced species with native species.
Maslin, B.R. et al. 2001. Acacia. In: A.E.Orchard & A.J.G. Wilson (eds.). Flora of Australia vols. 11A & 11B.
Key to species
1 Adult leaves all bipinnate without phyllodes (Subg. Botrycephalae) 2
1 Adult leaves all reduced to laminar phyllodes, rarely any bipinnate leaves 4
2 Leaves with 2-6 pairs of pinnae, pruinose A. baileyana
2 Leaves with 8-26 pairs of pinnae, not pruinose 3
3 Foliar raquis with 1 gland under each pair of pinnae A. dealbata
3 Foliar raquis with 2 glands below each pair of pinnae A. mearnsii
4 Adult leaves reduced to plurinervate phyllodes; spiciform inflorescences; Cylindrical; flowers tetramerous; pods cylindrical (Subg. Juliflorae) A. longifolia
4 Adult leaves reduced to uninervate or plurinervate phyllodes; flowers pentamerous, in globose glomeruli; ± compressed pod 5
5 Adult leaves reduced to plurinervate phyllodes; phyllodes with (2)3-5(6) prominent veins (Subg. Plurinerves) 6
5 Adult leaves reduced to uninervate phyllodes; phyllodes with a single prominent vein (Subg. Acacia) 7
6 Phyllodes elliptic-lanceolate, oblanceolate or subfalcate, generally more than 1.2 cm in width; glomeruli 10-12 mm in diameter, grouped in 2-8 into axillary clusters A. melanoxylon
6 Phyllodes linear-lanceolate or linear-oblanceolate, usually lessthan 1.2 cm wide; glomeruli 4-6 mm in diameter, solitary, axillaryor grouped in 2-3 into axillary racemes A. cyclops
7 Plant viscose; often some glomeruli geminateon the peduncle A. dodonaeifolia
7 Plant not viscose; glomeruli always solitary at the end of the peduncle 8
8 Phyllodes 0.5-5 cm wide; bracts promptly caducous; funicle white, short, not exceeding the seed in length 9
9 Phyllodes asymmetric at the base, falcate or subfalcate, muticous; racemes with 10-20 glomeruli; ± straight pod A. pycnantha
9 Phyllodes symmetrical at the base, linear to lanceolate, usually mucronate;racemes with (1)2-10 glomeruli; ± twisted-undulate pod A. saligna
Updated by: J.A. Devesa.