M. B. Bayer (MSc), Kleinbegin Farm, Kuilsriver, South Africa
Mrs Carly Cowell (MSc), Regional Ecologist, Cape Research Centre, Conservation Services, South African National Parks, Cape Town, South Africa.
Objective: The significance of the Park occurrences.
The occurrence of members of three aloid “genera” (the three sub-genera of the genus Haworthia could indeed be genera) and the absence of any other member of the Aloids (bar the ubiquitous Aloe ferox) must surely be indicative of the driving forces that determine the flora of the Park. This also must surely help establish the significance of the park as a conservancy of considerable merit. The complex interaction of the species enhances even that. The purpose of this report is to examine more closely the variation and nature of a small segment of the Park flora, and demonstrate how much more can be done.
Note: This report has several constraints. Firstly is the situation in which there is no formal general definition and hence understanding of what a plant species is. Secondly there is the generally understood view that there is an evolutionary process at work by which organisms evolve from a common distant origin by genetic mutation and adaptation. Thirdly there are serious flaws in the classification of the Aloid genera. Several essays dealing with these issues by DNA sequencing are weak because they rest on those flaws and consequently do not address some serious questions of relationships that the results pose. Fourthly of course is the reality that the knowledge or intellectual capacity to overcome these deficiencies may be absent. Thus the report is written in the context of all the publications as the original genus revision (Haworthia Revisited, Bayer; Umdaus, 1999) and others available on the internet (HaworthiaUpdates.org).
I was at Bontebok Park south of Swellendam this week specifically to get another look at Haworthia floribunda there and why it is so different. On the way I did some exploring at Stormsvlei about 25km west of Swellendam where I know H. mutica Klipport in a shale environment, and a very odd H. mirabilis growing on a small patch of manganic conglomerate. But going south onto the northern slopes of the Bromberg we found three populations of H. mirabilis in sandstone that are again “different” in the sense that “H. groenewaldii” could be different from H. mutica. This is just a local geological phenomenon and fully sequential with H. mirabilis to all compass directions. If you extrapolate this to Swellendam you have to conclude that the Swellendam mix of H. floribunda, H. marginata, H. minima, H. floribunda, H. mutica and H. retusa is the way it is because of the unusual geology of the area. The Bontebok Park is a relatively massive area of tertiary gravel of mostly river origin and derived from Table Mountain Sandstone. Tertiary gravels east and south are derived from silcrete and ferricrete. I do not know the detail of the mineralogy but it most definitely forms the basis of the soils, vegetation and habitat across the Southern Cape. I specifically looked at H. marginata in the park and see that it was in seed i.e. September flowering with massive capsules and seed. Now if Marx can persuade someone that this is a different species, I accept that I am a monkey’s uncle and that the differences in H. marginata elsewhere e.g. Drew, Bredasdorp and Heidelberg or Riversdale, mean there are several similar species. OH, I forget – that means H. floribunda would also be several species, and so is H. minima. But then H. mutica is of course several species and H. retusa several dozen. H. mirabilis several hundred.