African Wildlife & Environment Issue 82

FAUNA, FLORA & WILDLIFE

This tree is possibly the most common and widespread of any of our more than 1,000 SA trees and large shrub species (including woody climbers [=lianas]: see the Dendrological Society of South Africa’s 2014 Pocket List of Southern African Trees .) and an excellent summary in: Chapter 6, Vachellia (Acacia) karroo Communities in South Africa: An Overview , by Mamokete Dingaan and Pieter J. du Preez in a book titled Pure and Applied Biogeography . Additionally, there are a myriad publications and postgraduate studies on this species, and other African acacias. What one also needs to know is that this species is hugely variable across the many habitats where it occurs. From small trees in the Karoo that have been gradually spreading westwards, to skinny flagpole-like trees in Hluhluwe/Mfolozi Game Reserve, to large Copy of page 246 showing the distribution of A. karroo (here correctly shown as Vachellia karroo ) widely distributed over most of southern Africa

quick-growing spreading trees colonising bare coastal dunes in northern KZN. Some have almost smooth white trunks, rather than the usual brown to black rough bark of the karoo form. Jim Ross considered this was a species still evolving into several new species, and he chose to keep all seven of the variants he recognised as one entity. Jim was what we call a ‘lumper’. Subsequently, the ‘splitters’ have had a go at what was Jim’s A. karroo . and as a result, we now The much inflated spines on Vachellia leudereritzii are occuped by cock-tailed ants. In this case the twig is dead and the ants have vacated their temporary home. Please also note the much smaller, recurved, white spines elsewhere on the tree

Photos left to right A. karroo : Shoot of unlimited growth with PRIMARY leaves, followed by and older twig with SECONDARY leaves produced from a shoot of limited growth (middle), and finally a twig with an axillary branchlet of unlimited growth arising from a node where there are also leaves produced from a shoot of limited growth (above and below this are other leaves and inflorescences produced from shoots of limited growth). This is a complex arrangement that with careful observation, and some aid, you will be able to distinguish the difference. Little wonder many have not included information of these two distinctly, different shoot types (more on this matter in Episode 2)

34 | African Wildlife & Environment | Issue 82 (2022)