The Acacia debate

Botanical Congress, Media releases

A plant name dispute that has bubbled away for a decade has finally been resolved at the XVIII International Botanical Congress in Melbourne.
The species concerned are the acacias, which until now has included the Australian wattles and the thorn trees of the Serengeti—both highly recognisable and iconic groups of plants.

Kevin Thiele reports on the discussion

An important and controversial issue decided by the Nomenclature Section to put to the XVIII International Botanical Congress centred around the scientific use of the name Acacia.

Acacia taxonomy has generated much controversy in the scientific and wider community over the past decade. Careful research has shown that Acacia should be split into several genera, and a difficult decision was required as to whether the name Acacia should be used either for a very large group of species found mainly in Australia or for a smaller group found mainly in Africa and Central and South America.

Under the internationally accepted rules governing the correct naming of plants, the International Code of Botanical Nomenclature, the name would normally have remained with the African-American group, as this includes the species Acacia nilotica, which is the nomenclatural type species, the species which fixes the application of the genus name. However, a special provision of the Code allows for the name of the type species of a genus to be changed in cases like this, where strict application of the rules would require a large number of species to be renamed, and would cause confusion or significant difficulties for taxonomists or the wider community.

An application under this provision was made in 2003 by two Australian botanists who sought to make an Australian species the type species for Acacia. This was considered by the relevant botanical committees, who decided in its favour. The International Botanical Congress at Vienna in 2005 ratified this decision.

The proposal was highly controversial, however.  Acacia is an important genus in both Africa and Australia: in Africa it includes iconic and characteristic savannah species such as many flat-topped thorn trees, while in Australia it is the dominant genus over much of the continent and includes the Australian floral emblem (the Golden Wattle, Acacia pycnantha). The Vienna decision was contested by a group of botanists involved with African and American acacias.

In essence, the controversy in recent years focused on the procedure used in Vienna to vote on the Australian proposal. Those opposed to the decision argued that the Vienna meeting used a flawed process, while those in favour of it argued that the process was valid and correct.

The Melbourne Congress, in two important votes on the first day of the Nomenclature Section, supported the procedure used in Vienna by a large majority. Support for this decision was widespread and not confined to Australian delegates. This vote effectively confirmed that the type species of Acacia is now an Australian species.

Later in the Nomenclature Section meeting, proposals were considered to amend the rules under which plants are named, to allow a “compromise solution” to the Acacia problem. One proposal would have allowed botanists to continue to use the name Acacia for all the segregate genera; a second proposal would have created new names – Austroacacia and Protoacacia – for the Australian and African-American groups respectively.

Delegates at the Section voted, again by large majorities, to reject these compromise proposals. While many expressed an understanding of the difficulties caused by the renaming of the African-American acacias, many argued that the compromise proposals unacceptably compromised the rules of nomenclature and created a dangerous precedent.

In summary, the decisions taken in Melbourne confirm that the Australian acacias retain the name, while a new name is needed for the African and American species. Several options for achieving a good result in Africa and the Americas are available, and will be discussed and considered in the months ahead.

For more information:  call me on 0417 131 977, or AJ Epstein on 0433 339 141 or email We’ll be in the Media Room (214 from 8:30am Monday 25 July).