Nature drawings

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.

My indigenous courtyard garden

This is my spring patio garden which gets just the right amount of sunlight to make the plants happy. There are mainly indigenous plants here, including a pelargonium, plakkie (Cotyledon orbiculata) and an arum.
Thembisa Kohli, Khayelitsha

Sticking nails into aliens

As a member of the Western Heads/Goukamma conservancy in Knysna we struggle with the ongoing problem of alien tree control, especially pine and black wattle that infests some of the fynbos areas. Cutting and ring barking these two species respectively is as you know, expensive and time consuming for individual landowners.
The question I’d like to pose to people in the know is firstly, what is the world’s most toxic chemical agent to all trees and is this agent able to be infused into or coated over a type of hard metal nail that can be knocked into a tree once, which over time releases the toxins and eventually kills the tree? Imagine a box of say, one hundred nails no longer than 10 cm. each, which in half a day’s work could be hammered into select large alien trees which never have to be either chopped up, removed or cleared but only left to stand and slowly die from the root up and naturally rot away.
I look forward to sharing your readers ideas.
Guy Thesen

Who has the most species of us all?

Fynbos on the Cape Peninsula. Photo: Alice Notten.

Fynbos is said to have the most plant species and cover the smallest area, yet they say the tropical rainforests have more species. What am I misinterpreting regarding our fynbos?
Ronnie Glass

Alice Notten, Kirstenbosch, replies
I think the confusion arises from the way it is measured and compared.The figures that John Manning gives in his book Field Guide to Fynbos are species per 1000 km², calculated by dividing the total number of
species by the surface area covered by that vegetation type. He says that the entire Cape Floristic Region (that includes fynbos, renosterveld and succulent Karoo) averages 94 unique species per 1000 km². The
similar heathland communities of California and southwestern Australia average 14 and 12 unique species respectively. Southern Africa as a whole averages out at 8 unique species per 1000 km². Taking just
the fynbos areas within the Cape flora, he gives an average of 150 to 170 unique species per 1000 km². Using this method fynbos figures are two or three times that measured for tropical rainforests (this figure for rainforests is not given in his book). So fynbos has a high number of species packed into a tiny area. The other way of measuring is to measure out a quadrant and count the number of species found in that quadrant. On this scale the rainforests come out on top. Tropical rainforests range between 130 and 190 species, fynbos has 65, Renosterveld has 85 and California heathlands have 30.
Why then does fynbos show diversity but not remarkable diversity on the local richness scale yet enormous diversity for the vegetation as a whole? Fynbos diversity does not lie in the number of species found at any
particular site, it lies in the proportion of species shared between sites, i.e. fynbos has an exceptionally high number of highly localized species – species that are restricted to a single small area. If you look at the species lists for quadrants only kilometers apart, between half and two thirds of the species will be different for fynbos whereas in the rainforest the same species are scattered widely over a large area. Thus you will find more species per square kilometer in a rainforest than you will in fynbos, but if you move to another square kilometer, the fynbos species will have changed whereas those for the rainforest will remain much the same, so in total fynbos counts up more species over the whole area it covers than rainforests.

Floral mimicry

We recently hiked on Anne Paterson’s farm in the Cedarberg and we
saw these flowers of Lapeirousia fabricii (left) and Tritonia crispa (right) growing next
to each other. We were very excited because we had never seen the
tritonia before. It apparently only flowers after fire, and the veld was
burnt a year or so before.
Micky Orrey, Cape Town

Graham Duncan of Kirstenbosch replies
An excellent example of floral mimicry – both Lapeirousia fabricii and
Tritonia crispa are adapted to pollination by long-proboscid flies.