What’s in a name?

Tree Wistaria Bolusanthus speciosus. Photo: Caroline Voget.

Not only are the scientific names of plants changed from time to time but so are their common names. Why is this so? The whole process of botanical nomenclature in the scientific sense is strictly controlled by international convention and rules (for example the whole Acacia name change debate). Plants are named officially using a binomial system of genus first (and with a capital letter) followed by the species (lower case). Thus for example we have Acacia karroo; a widespread and common tree species in South Africa. Also by convention all binomials are written in italics. To be even more precise one should follow the binomial with the author or authors (the authorities who first named the plant by publishing a description which by ‘law’ must be in Latin). Thus strictly speaking it is Acacia karroo Hayne. To be even more pedantic some authorities have internationally accepted abbreviations; thus, for example, Linnaeus is not spelled out in full but written as L. (in bold and with a full stop). And, for example, the ‘baobab’, Adansonia digitata L., still has the same scientific name it was given in the mid-1700s.

Exploding the myth

Grassland in the Drakensberg foothills with a lone Cabbage Tree (Cussonia paniculata). Photo: Eugene Moll.

Fire and frost keep trees from establishing in the grasslands of the Highveld is an oft-perpetuated myth. Back in the late 1950s, an exceptional South African geomorphologist, Lester King, published his book The South African Scenery in which he questioned many existing geological paradigms, and Ken Tinley put forward his view of why the Highveld was treeless. Tinley’s view was certainly very different from what I had been taught, and what is still taught today – that frost and fire keep the Highveld grasslands treeless. What rubbish!
As I remember it, the reason for King’s book was that he had submitted a paper on the age of South African mountains and the peer-reviewed journals (in the Northern Hemisphere) all refused to publish his work. At that time geologists believed that there were no mountains on Earth older than 10 million years! Yet King was telling the world that the Cape Fold Mountains were older than 70 million years old and that we had some land-surfaces that hark back to the break-up of Gondwana (the Highveld). Today his pioneering work has been vindicated. Thankfully today’s scientists have become much more open-minded since those oppressive and restrictive days of the mid-1900s. Recently a University of Cape Town group researched the reasons for no trees in the Highveld grasslands (see the article ‘Why do grasslands have no trees’ by Julia Wakeling, William Bond and Michael Cramer in the March 2009 issue of Veld & Flora). Their conclusions were inconclusive, but they certainly demonstrated that frost is not a totally limiting factor, nor were fires a conclusive reason for no trees but that the lack of trees could be due to a combination of factors; one of which may be plant available nutrients. Thus the generally held view that grasses dominate the Highveld because it is too cold for trees and that fierce annual fires kill woody growth has been debunked.