The Vachellia karroo-complex
Preface
In 2011 the change from Acacia to Vachellia or Senegalia for the African Species has been accepted by the Nomenclature Section of the XVII International Botanical Congress in Melbourne, Australia, confirming the Vienna Code from 2005.
In 2013 a group of South African authors ( Kyalangalilwa et al. ; Botanical Journal of the Linnean Society, 2013) renamed most of the African Acacia s.l. species.
Nevertheless the tree-list of the Dendrological Society of South Africa has not been changed till today.
http://www.dendro.co.za/fsa-tree-names--numbersfsa-boom-name--nommers.html
Accordingly neither the 3rd edition of PALGRAVE (2002), nor the 2nd edition of the „Field Guide to trees of Southern Africa“ by B. van Wyk and P.van Wyk (2013) have adopted the change.
Only in ispot, an internet platform of SANBI the new names are cautiously applied by some members.
Hence I have to use the old names to discuss the status of the Vachellia (Acacia) karroo-complex.
The Acacia (s.l.)-karroo complex, Status 2014
Since my last comments on this matter (2003) see below
some additional information is available. In the recent 2nd edition oft the Tree Field Guide from van Wyk & van Wyk (2013) two of the 6 new (separated) species are mentioned:
Acacia kosiensis (Dune sweet thorn) with 5-7 pair of pinnae (p/p), a light brown or greyish white bark and constrictions between the seeds on the pods. This species is confined to a small coastal strip in KwaZuluNatal.
And Acacia natalitia (pale barked sweet thorn) with 6-12 p/p and a greyish white bark, with a wider distributuion, replacing Acacia karroo east of the Great Escarpement area in the summer rainfall region.
Palgrave (2002) lists five new species. A new aspect in the species-differentiation is the separate discussion of distal and proximal leaves. The proximal leaves mostly show less p/p than the distal ones in the new species:
Acacia dyeri is a shrub to 1m height in an small area north of East London; 3-5 p/p; „very long flowering period so that both flowers and ripe pods can be found on the same branch at the same time“.
Acacia kosiensis occuring on a narrow coastal strip in KZN. Interestingly ...“ this is the only species within the previous A. karroo-complex, with flavanoids in the wood and hardly any tannins in the bark“.
Acacia natalitia with 6-12 distal p/p (no indication of number of proximal p/p).
Acacia robbertsei, confined to a small area in Sekhukhuneland. It has densely hairy pods and leaves are densly hairy all-over.
Acacia theronii was renamed A. montana in Palgrave (I do not think that is correct as discussed in the NEWS-section of this internet-site in Oct 2013). It shows 3-4 distal and 1-2 proximal p/p. And it is only found in a limited area between Mpumalanga and Sekhukhuneland.
Acacia karroo has the widest distribution (including Namibia) but the species s.s. is confined to 2-3 p/p in the description in Palgrave. The illustration Nr. 60, however, clearly shows leaves with up to 6 p/p!
Vachellia ebutsiniorum is not mentioned in the Field Guides. It seems to have a very local distribution in Mpumalanga, Ebutsini tribal land.
Only on ispot the new nomenclature is used e.g. for Vachellia kosiensis:
http://www.ispot.org.za/node/225089
Outlook
It seems to me, that there is still much work to do regarding the separation of species in the Acacia karroo-complex and define the characteristics of the remaining species Vachellia karroo. I can only repat my earlier question: How to call the tall Acacia karroo-trees with 6 or more pairs of pinnae, described by Carr (1976, page 68), shown in the literature or on the internet (e.g. my home page: http://acacia-world.net/index.php/africa-me/namibia/acacia-karroo
and
http://acacia-world.net/index.php/africa-me/south-africa/vachellia-karroo-s-l)
and often found in South Africa and Namibia, i.e. in other areas than described above?
Earlier comments: In his 1976 book The South African Acacias, J.D. Carr notes that “the species varies considerably in overall appearance, size and other characters and the layman may be justified in expressing surprise that the differences have not been considered sufficiently marked to warrant division into subspecies, or at least varieties.”
Regarding the foliage he writes: “Typical” pinna pairs number generally from 3 to 5, but 12 and even 16 have been noted from the N. and E. Transvaal these latter possibly coming from a further variant. The book shows a picture of an A. karroo leaf from the Barberton district with more than 7 pairs of pinnae.
The 1999 Guide to the Acacias of South Africa by Nico Smit still keeps Acacia karroo as one species, but talks of a gene-pool and mentions several “untypical” forms.
In 2002 the third edition of Trees of Southern Africa by M. Palgrave cites four new species derived from the Karroo-complex as described by P.P.Swartz , three of which received tree numbers by the Dendrological Society of South Africa (only A. dyeri is missing in that list). Also A. natalitia, the “KZN-form of A. karroo”, often showing a whitish bark, was reinstated and got its own tree-number.
There are now the following six species/varieties in the A. karroo-complex:
Acacia dyeri
Acacia karroo
Acacia kosiensis
Acacia natalitia
Acacia robbertsei
Acacia theronii (initially named A. montana by P.P.Swartz).
Some explanations how to differentiate them are given by Eileen Campbell in the Newsletter 4th Quarter 2003 of the Algoa Branch of the Botanical Soc. of South Africa.www.botanicalsociety.org.za
Analysing her article I distill out the distinguishing characteristics for:
A. dyeri: a shrub with many stems originating from the root, always shorter than 1m, endemic to the grass-veld of Kei River Mouth area north of East London.
A. karroo: is a tree, although branching very close to the ground. It has 2-3 (max.5) pair of pinnae A. kosiensis: 10-17m high, yellow powder-puff inflorescence hidden among the leaves; rachis and rachillas are finely hairy, but leaflets are without hairs. Along KZN-coast north of Tugela River to Mocambique.
A. theronii: 4-6- m high, flowers and ripe pods together on tree.
A. robbertsei: 6 or more pair of pinnae; all parts of the compound leaf are densely hairy.
A. natalitia described by N. Smit as a white-barked tree or shrub with short spines and 4 - 13 pinna pairs per leaf, mainly found in the Eastern Cape, KZN, Swaziland, Mpumalanga, Zimbabwe and Mocambique.
A. karro s.s. is limited to a maximum of 5 pair of pinnae. That leaves the tall Acacia karroo-trees with more than 6 pairs of pinnae, described by Carr, shown in the literature or on the internet and often found in South Africa and Namibia, i.e. in other areas than described above, without a name. I suggest a broader genomics study of this group - as is actually been done with the very difficult group of A.aneura (Mulga) in Australia by. J. Miller et.al.
Gums are secreted at wounds