African Wildlife & Environment Issue 83

FAUNA, FLORA & WILDLIFE

Acacia karroo Episode 2 - A Few Final words

It is fitting to start this, my final piece, in the recent past, since during this time the genus Acacia has enjoyed southern African, African and global attention amongst botanists, citizen scientists and the general public. This because of the uproar caused when the botanical, taxonomic world, at the International Botanical Conference in Melbourne, Australia (2011), put the ‘ final nail into the coffin’ when it was confirmed that the name ‘Acacia’, derived from the Greek ake and/or akis referring to a sharp point, be conserved for the vast majority of the non-spiny Australian members of the genus! Historically the genus name was given to an African species by Linnaeus in 1773 after the term coined by Pedanius Dioscorides, well before Christ, that was applied to Acacia nilotica from Egypt (see Clarke & Charters, 2016, Illustrated Dictionary of Southern African Plant Names, Jacana Media). A year or so before, and indeed after 2011, people tried to contest the name change. Note that this change was done strictly in accordance with the laws laid down for taxonomic name-changes, according to the rules governing international botanical nomenclature. Frankly, and in the final analysis, we just have to accept this change scientifically. However, in common use, there is nothing illegal in referring to our thorny trees as ‘acacias’, which I shall do forever. But if I were to write about acacias in the peer-reviewed literature I must follow the correct nomenclature! So, please, no more amateur attempts to get the old name back – that is simply Not surprisingly, there are still a few loose ends for me to tie up regarding this amazing, essentially southern African, tree species and Karoo super-hero! This essay, and my other contributions on A. karroo are not only about the taxonomy, ecology and possible evolutionary forces that moulded this species to be so iconic and successful in the southern parts of South Africa (see AW&E #80 & #82), but also include thoughts about the whole genus - that once numbered over 100 well known and recognised African species!

Eugene Moll

a waste of time and effort, notwithstanding any argument you may wish to make. That matter is Q.E.D. ( quod erat demonstrandum ) - as I was taught in high school geometry after having proved a theorem! What did emerge from this taxonomic change in 2011 in fact proved to be a positive step forward, when we learned that our species of acacia belong to two different genera (three if you consider Faidherbia albida - that was once Acacia albida ). Today those acacias that have spike like inflorescences and hooked prickles (‘prickles’ being spine-tipped outgrowths that have no vascular tissue) are in the genus Senegalia , and those with pom-pom like inflorescences and paired, stipular spines (spines have vascular tissue so cannot easily be removed), are Vachellia . Before you ‘complain’ about this further split/name change, consider some fairly recent research that informs us that these two essentially savanna/ bushveld species left the primeval forests at different times (see AW&E # 82: Vachellia ~8 Ma and Senegalia ~5 Ma) and each genus developed different strategies to withstand browsing by large mammals ( Veld & Flora , December 2021). So not only are our ‘old’ acacias, now in two different genera, but the two genera also differ ecologically (how cool is that?). I find this extremely interesting and intellectually challenging – because one can now speculate about the how and the why these two sympatric Bushveld genera have thrived through the ages in different ways!

24 | African Wildlife & Environment | Issue 83 (2023)