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Acacia name issue

Acacia has now been conserved with a new type, A. penninervis DC. that replaces the former type, A. scorpioides (=A. nilotica) (McNeill & Turland, 2011). This issue has been the subject of a robust debate in scientific and other literature over about the past two decades. However, the matter now appears to have been be resolved and nomenclatural stability has been achieved insofar as the appliction of the name Acacia is concerned. This nomenclatural matter is inextricably linked to the division of Acacia sens. lat. which is discussed elsewhere on WorldWideWattle.

Adoption of new names that are now applicable to species of Acacia sens. lat. has been occurring over the past decade in a range of literature, databases, web resources, etc. Although this process continues (and is gaining momentum), universal uptake of the new nomenclature will take time, especially given the large size and global distribution of the group, and the dispute concerning the application of the name Acacia itself.

The following notes provide a terse overview of these nomenclatural issues and a summary of the present uptake of the new names. Relevant background information is presented under the Further details heading.

Synoptic overview

In modern times the issue of splitting Acacia sens. lat. commenced with Pedley (1986), who proposed recognizing three genera, Acacia, Senegalia and Racosperma, the latter being a resurrected name that would encompass most Australian species; however, the proposal was not widely adopted at the time. The issue gained momentum around the turn of the century when molecular and other evidence indicated that the group was indeed polyphyletic and that at least five genera needed to be recognized (see Maslin et al. 2003 for overview). The impending split of Acacia sens. lat. prompted Orchard & Maslin (2003) to formally propose, in the interest of perceived nomenclatural stability, that the name Acacia be conserved with a new (Australian) type. The proposal generated much debate before and during the Nomenclature Session of the International Botanical Congress (IBC) in Vienna in 2005, but was accepted at that Congress. This outcome meant that: (1) the name Acacia (syn. Racosperma) applied to the "Australian group" of species and (2) in Africa, America and Asia the name Acacia would no longer apply to species belonging to the former Acacia subg. Acacia (these species would become known as Vachellia). Following the decision at Vienna some delegates raised questions about procedures adopted in the Nomenclature Session. Furthermore, due to the large size and global distribution of Acacia sens. lat. and the symbolic significance of the name Acacia (particularly in Africa and Australia), it was inevitable that not everyone would be happy with the Vienna outcome. Consequently further debate ensued and the matter was ultimately brought before the Nomenclature Session of the IBC in Melbourne in 2011. Following lengthy discussion at that meeting the decision of the Vienna Congress was ratified. This means that Acacia with its conserved type remains in the International Code (McNeill et al. 2012).

Adoption of new generic nomenclature

A summary of the uptake of the new nomenclaure within Acacia sens. lat. following the split of the group and the retypification of the name Acacia is given in Maslin (2015). Much of the following information is taken from that publication.

Combinations have been made for practically all the currently recognised species of Acacia sen. lat. that are referable to Acaciella, Mariosousa, Senegalia and Vachellia. These new names (and their Acacia analogue name when that group was treated as a single genus) can be accessed via the WorldWideWattle Search feature. The only species known at present (Nov. 2015) that may possibly require a new combination (in Vachellia) is Acacia pennivenia Balf.f., which is endemic in Socotra (an island off the Horn of Africa).

After the Vienna IBC, the "new" generic names had begun to appear in a range of publications and web databases. As summarised by Maslin (2011), even prior to the Melbourne IBC the name Vachellia had been adopted, in lieu of Acacia, in many publications including Flora treatments, field guides, scientific research papers and books. One particularly important publication to adopt the new nomenclature early was Mabberley's Plant-book 3rd ed. (Mabberley 2008), which is a primary reference source for the correct names of vascular plant genera and families of the world.

On the web today the new nomenclature has now been adopted in some large databases such as the Catalogue of Life and the National Center for Biotechnology Information. Others web resources such as Tropicos and The Plant List currently adopt a half-way approach by listing many names as accepted under both Acacia and Vachellia/Senegalia. Some important legume-centric databases on the web still maintain the old nomenclature, e.g. the online version of Legumes of the World and the International Legume Database & Information Service (ILDIS). Furthermore, the online version of Index Nominum Genericorum still lists A. scorpioides as the type of Acacia. There are of course many possible reasons why the uptake of the new generic nomenclature has been slow, erratic or has not occurred at all. Resource and time limitations are two of the more obvious reasons, but some databases may simply not have the capacity to be changed (ILDIS is presently in this latter category).

In Asia the new names have begun to appear on the web with Senegalia being listed for both the Philippines and for the Hengduan Mountains region of south-central China. Ali (2014) has adopted the new names for Pakistan. Also, the new generic names have been adopted in the checklist of plants of China and India that are expected to be published soon.

Although the new nomenclature has been adopted (at least in literature) in many parts of the world the uptake of the new names by herbaria appears to have been relatively slow. If this is the case then it is not surprising because implementing changes for such a large group poses practical problems for many herbaria. Austrailan herbaria have adopted the new nomenclature (and the names are incorporated into the Australian national names database) but in Australia there are relatively few specimen records and names involved. For herbaria with large holdings of Acacia sens. lat. it is more difficult to implement the necessary change (see Maslin 2015 for discussion).

Further details...

The following discussions provide some historical information concerning the conservation of the name Acacia.

Melbourne IBC (2011)

In July 2011 the Nomenclature Section of the XVII International Botanical Congress in Melbourne, Australia, voted with a clear majority (68%) to accept the Vienna Code with Acacia included therein with a conserved (new) type, A. penninervis, that replaces the former type, A. scorpioides (=A. nilotica). The consequence of this decision is that when Acacia sens. lat. is regarded as comprising segregate genera the name Acacia applies to the large, predominantly Australian group that was formerly called Acacia subgenus Phyllodineae; the name Racosperma is a synonym of this group. Also, the name Vachellia is the correct name for the smaller, pan-tropical group that was formerly called Acacia subgenus Acacia.

Following the Vienna IBC in 2005 some workers had questioned the validity of the procedures adopted there that first effected the conservation of Acacia with its new type. The opposing views in this debate are best summarized in the following two papers (both of which contain additional relevant references on this subject):

  1. Moore et al. (2010) focused on details of the process by which the vote was conducted in Vienna, arguing that it was flawed and therefore stated their intention to challenge the decision at the Melbourne IBC.
  2. Thiele et al. (2011) argued that the Vienna process was fundamentally sound, that reversing the decision, except through standard processes as suggested by McNeill & Turland (2010), would set a dangerous precedent and therefore the Vienna decision should stand.

Resolution of these two diametrically opposed views was contingent, in the first place at least, on whether or not the Nomenclature Section of the Melbourne IBC accepted or rejected the Vienna Code with Acacia included with its conserved type as basis for discussion at that meeting. The matter was put to the vote and a clear majority (68%) voted in favour of accepting the Vienna Code with Acacia included; a breakdown of the voting patterns is shown in Table 1 below. Because of the widespread global impact of this decision, and because this generic issue had been such a controversial issue, attempts were made to attain a compromise whereby neither side of the debate would feel disadvantaged: two main compromise proposals had been published ahead of the meeting, one by Brummitt (2010) and another by Turland (2011), but neither received sufficient support to be accepted.

The outcome and consequences of the Melbourne Acacia decision were published at the IBC in the 26 July issue of Congress News; a fuller account of the discussions is provided by Smith & Figueiredo (2011).

Many people expected (or at least hoped) that decisions made at the Melbourne IBC would put an end to the nomenclatural destabilization surrounding the application of the name Acacia. It is therefore regrettable that Smith & Figueiredo (2011) have stated that it is likely that yet another conservation proposal will be made, one that will aim to return Acacia to its original type (A. scorpioides). Any such proposal will of course need to be assessed by the relevant Committees of IAPT and if successful, will then need to be ratified by the next Botanical Congress that will be held in 2017 in China. Given the very extensive debate and deliberations by the global taxonomic and nomenclatural community that have already occurred regarding the application of the Acacia, it is difficult to see the justification for protracting this matter further, or how any such proposal will be in the interest of global nomenclatural stability. Surely it is now time to move on! (Note: as of Nov. 2015 no such proposal has been forthcoming.)


Total votes case (545)

Institutional votes cast (383)

Personal votes cast (162)

For acceptance

Against acceptance

For acceptance

Against acceptance

For acceptance

Against acceptance

373 (68.4%)


247 (64.5%)


57 (61.3%)


Table 1. Voting pattern at Melbourne IBC for acceptance of the Vienna Code with Acacia included with its conserved type. The figures provided below are derived from McNeill et al. (2011).

Vienna IBC (2005)

On 16 July the Nomenclature Section of the XVII International Botanical Congress in Vienna , Austria , voted to accept the Spermatophyta Committee's recommendation to conserve the name Acacia by retypifying it with a new type as proposed by Orchard & Maslin (2003). This decision was subsequently ratified at the Plenary Session of the Congress on 23 July. The new type of Acacia is the Australian species A. penninervis (replacing the African/Asian species, A. nilotica). The above decision means that when this large cosmopolitan genus is split the name Acacia will be retained for the almost 1,000 species currently ascribed to Acacia subgenus Phyllodineae; these species predominate in Australia and are extensively utilised around the world. The majority of native, non-Australian species will subsequently become known as either Vachellia or Senegalia. The information presented below provides some details relating to this issue.

  • Acacia - the final decision. A discussion paper by Bruce Maslin & Tony Orchard providing terse background information on the Acacia name issue, a précis of events leading up to the Vienna Congress, and reasons why the Congress voted the way it did.
  • List of people who expressed support for the Spermatophyta Committee's recommendation to accept the Orchard and Maslin proposal to conserve Acacia with an new type. Worldwidewattle extends it sincerest thanks to the almost 250 people who provided this support. Glenda Lindsay is also thanked for assistance in preparing this list. Contact us if your details need changing or if we inadvertently omitted to list your name.
  • Chronology of relevant matters concerning the proposal to conserve Acacia with a conserved type (since March 2003)

Some pre-Vienna Background Information


Ali, S.I. (2104). The genus Acacia s.l. in Pakistan. Pakistan Journal of Botany 46: 1-4.
Brummitt, R.K. (2010). Acacia: a solution that should be acceptable to everybody. Taxon 59(6): 1925-1926.
Mabberley, D.J. (2008). Mabberley’s Plant-book 3rd ed. Pp. 1021. (Cambridge University Press: England,Cambridge.).
Maslin, B.R. (2011). Acacia and the IBC. Australasian Systematic Botany Society Newsletter 146: 2-6.
Maslin, B.R. (2015). Synoptic overview of Acacia sensu lato (Leguminosae: Mimosoideae) in East and Southeast Asia. Gardens’ Bulletin Singapore 67(1): 231–250.
Maslin, B.R., Miller, J. & Seigler, D.S. (2003). Overview of the generic status of Acacia (Leguminosae: Mimosoideae). Australian Systematic Botany 16(1): 1-18. An abstract of this paper (together with a provision to purchase the whole article) is available from CSIRO Publishing.
McNeill, J., Barrie, F.R., Buck, W.R., Demoulin, V., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Knapp, S., Marhold, K., Prado, J., Prud’Homme van Reine, W.F., Smith, G.F., Wiersema, J.H & Turland, N.J. (2012). International Code of Nomenclature for algae, fungi, and plants (Melbourne Code). Regnum Vegetabile 154. pp. 208. (Koeltz Scientific Books: Germany.)
McNeill, J. & Turland, N.J. (2010). The conservation of Acacia with A. penninervis as conserved type. Taxon 59(2): 613-616.
McNeill, J. & Turland, N.J. (2011). Major changes to the Code of Nomenclature – Melbourne, July 2011. Taxon 60: 1495–1497.
McNeill, J., Turland, N.J., Monro, A.M. & Lepschi, B.J. (2011). XVIII International Botanical Congress: Preliminary mail vote and report of Congress action on nomenclature proposals. Taxon vol. 60, no. 4. (Note: The pdf provided here is the independently paginated  version of this paper that was posted on the Taxon Fast Track on 12 Sept. 2011; this paper will soon become available under volume 60 on the Taxon site.)
Moore, G., et al. (2010). Acacia, the 2011 Nomenclature Section in Melbourne, and beyond. Taxon 59(4): 1188-1195.
Orchard, A.E. & Maslin, B.R. (2003). Proposal to conserve the name Acacia (Leguminosae: Mimosoideae) with a conserved type. Taxon 52(2): 362–363
Smith, G.F. & Figueiredo, E. (2011). Conserving Acacia Mill. with a conserved type: What happened in Melbourne?" Taxon 60(4). . (Note: The pdf provided here is the independently paginated  version of this paper that was posted on the Taxon Fast Track on 12 Sept. 2011; this paper will soon become available under volume 60 on the Taxon site.)
Thiele, K., et al. (2011). The controversy over the retypification of Acacia Mill. with an Australian type: a pragmatic view. Taxon 60(1): 194-198.
Turland, N.J. (2011). A suggested compromise on the nomenclature of Acacia. Taxon 60(3): 913-914.

Page last updated: Thursday 22 June 2023