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Acacia name issue

Melbourne 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).

Where to from here?

There is now considerable morphological and genetic evidence indicating that Acacia sens. lat. is polyphyletic and that a number of separate genera should be recognized within the group; Maslin (2011) provides reference to the most recent genetic papers. Table 2 below summarizes the current generic classification of Acacia with five genera recognized. Of course, if one chooses not to recognize separate genera then the name Acacia can be applied to the broader group.

A number of combinations are still required in both Senegalia and Vachellia and it is hoped that someone will soon undertake this work so that a full complement of names will become available for use in broad-based comparative studies involving Acacia sens. lat. A list of Acacia sens. lat. taxa for which names are required in Vachellia and Senegalia is provided here.

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!


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).


Post-Vienna names; Acacia s.l. treated as five genera

Pre-Vienna names (Acacia treated as a single genus with A. scorpioides the type).

With A. penninervis the type

With A. scorpioides the type






    subg. Acacia








    subg. Aculeiferum
        sect. Spiciflorae








        sect. Filicinae








        sect. Acacia coulteri group








    subg. Phyllodineae








Table 2. The classification of Acacia sens. lat. showing species numbers and major areas of occurrence. Numbers are sourced from current information at Species Gallery on WorldWideWattle and refer to accepted species only (not including infraspecific taxa, informal taxa or hybrids).


Brummitt, R.K. (2010). Acacia: a solution that should be acceptable to everybody. Taxon 59(6): 1925-1926.
Maslin, B.R. (2011). Acacia and the IBC. Australasian Systematic Botany Society Newsletter 146: 2-6.
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., 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.
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.

Vienna 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)

Generic and Infrageneric Names

Generic and infrageneric names in Acacia following retypification of the genus. By B.R. Maslin (Nov. 2005, revised July 2006)

Some Background Information

  • Wattle become of Acacia? A simplified version of the taxonomic and nomenclatural issues relating to the impending division of Acacia.
  • Proposal to conserve the name Acacia (Leguminosae: Mimosoideae) with a conserved type. Formal proposal by Orchard and Maslin to retypify Acacia with a new type (a hyperlink to the internet version of the journal published by the International Association for Plant Taxonomy in which this proposal appears, namely, Taxon 52(2): 362-363, 2003).
  • Nomenclatural and classification history of Acacia . An unpublished paper by Maslin, Orchard and West providing background and supplementary information relevant to the Orchard and Maslin (2003) proposal to conserve the name Acacia . (This is essentially a detailed version of the 'Wattle become of Acacia' article that is listed above.)

Further Information

Additional information on the taxonomy of Acacia is presented elsewhere on Worldwidewattle.

Page last updated: Wednesday 6 November 2013