Soutpansberg centre of endemism and biodivesity
As a result of the decline and elimination of various large mammals and the introduction of livestock such as cattle and goats, secondary bush encroachment has replaced much of the original grassland vegetation. At present many rare and endangered mammals are still to be found within the Soutpansberg. Habitat degradation and poaching could have a marked influence on their survival.
The avian fauna is immensely diverse, ranging from species confined to the forest (Macheiramphus alcinus, Bathawk) to species commonly associated with the savanna vegetation of the surrounding area.
The insect fauna has been poorly studied. However, many endemic species, especially butterflies have been found. There seems to be a definitive disjunct distribution between the endemic butterflies occurring in the Soutpansberg, and those occurring in the Blouberg.
The Soutpansberg is known for its substantial number of restricted reptile species. Branch (ed.) (1988) considers the Soutpansberg and adjacent regions a sensitive area, having recorded eight restricted taxa of which seven are endemic to the mountain region.
At present no endemic fish have been recorded in the Soutpansberg. This could be attributed to the immense age of the Soutpansberg and possibly through periodic droughts which lead to mass extinction of fishes.
One endemic frog Breviceps sylvestris taemiatus Poynton has been recorded for the Soutpansberg. Its nearest ally B. s. sylvestris FitzSimons occurs in the Wolkberg region a distribution shared with some of the endemic plants. The Soutpansberg has a relatively poor representation of frog species, an attribute shared with the fish. It is possible that the factors pertaining to the fish diversity are also relevant to those of the frogs. The only frog genus that has an endemic representative is Breviceps, a fossorial genus that is capable of aestivation. It is also the only group of frogs which do not need water for the development of their offspring making it more tolerable towards the survival of droughts.
Cowling & Hilton-Talor (1997) pointed out that there is a direct correlation between species richness and high endemism in southern Africa with the exception of Kaokoveld and Karoo Centres.
Approximately 2 500 to 3 000 vascular plant taxa comprising 1 066 genera and 240 families are known to occur in the mountain. This is a significant number if one hade to compare it to other regions. Arnold and De Wet (ed.)(1993) recorded 2 604 genera and 353 families for the entire Flora of southern Africa region (South Africa, Namibia, Botswana, Swaziland and Lesotho). The Soutpansberg therefore contains 41% of all plant genera and 68% of all plant families of the Flora of Southern Africa region. Altogether, 38 plants taxa are known to be endemic to the Soutpansberg, comprising 27 genera and 17 families.
Altogether, 594 tree taxa are known in the Soutpansberg, one of the highest counts for southern Africa, and approximately one third of all known trees of southern Africa. This is a significant number representing 18% to 22% of the known flora of the mountain range. It is therefore no wonder that most vegetation types within the area are predominantly woodlands.
Approximately 10% of the plants occurring within the Soutpansberg can be considered succulent. 32% of the endemic flora of the mountain can be regarded as succulents.
A succulent could be define as a plant which has the ability to store water in one or more of its morphologic components. This water being used when the plant is unable to absorb moisture through it normal means namely its roots. Nonetheless the plant will need a period where it must replenish his reserves.
From this we can deuce that whatever conditions arouse towards there evolution had to be related to periods of water stress. This would suggest that succulent endemics are the prodigies of a far distant relative that inhabited the area in times of lower than average moisture perspiration that became isolated as the climactic situations improved. It therefor becomes clear that the Soutpansberg throughout its history has undergone periods of drought leading to the isolation of biological entities.
Of the known endemic taxa, no fever than 17 can be considered succulent, with eight being leaf succulents and nine stem succulents. Eight taxa can be considered trees, that is to say woody or semi-woody plants growing taller than 2 m. The greatest generic diversity within a family is displayed by the Asclepiadaceae with five genera and six species. Aloe show the greatest species diversity with five species. The monotypic genus Zoutpansbergia is the only genus endemic to the mountain entailing one species. 24 species are found within the mist-belt with 13 restricted to Of these 13 species confined to the mist belt seven are succulents, two are trees, one an epiphyte one and one a herb.
Approximately 63% of the endemic species occur within the mist belt region where of no fever than 34% are restricted to it. In times of drought a large percentage of the high altitude mountain flora survives on the mist. Very little is known about mist and its interaction with the environment. At Entabeni mist precipitation has been measured at an average of 1 366 mm per annum (Department of Environmental Affairs 1988). Taking into account Entabenis average annual rainfall of 1 867 mm, the average total meteorological precipitation is 3 233 mm per annum.
Edifice speciation has played an important role in the evolution of the southern African endemic flora. In the Cape Centre the highest levels of endemism are associated with fynbos vegetation on nutrient poor soils largely dived from ancient, sterile quartzites (Cowling 1983). In the Wolkberg 71% of the endemics occur on soils derived from nutrient-poor quartzites (Matthews et al. 1993). The Pondo Centre is exclusively associated with an outcrop of ancient quartzites (van Wyk 1994). Most of the Maputuland endemics occur on infertile sandy soils mostly associated with see sand (van Wyk 1994). In both the Eastern Mountain Centre and Wolkberg Centre most endemics are associated with grassland habitat (Hilliard & Burtt 1987; Matthews et al. 1993). Almost all of the Chimanimani endemics occur on quartzites (Wild 1964). As Wild (1964) stated these soils form a very unfavourable habitat from an evolutional point of view.
With the exemption of the epiphyte, all taxa mentioned above grow in sandy soils derived from quartzite or sandstone. Euphorbia sp. nov. (N. Hahn 531). Duvalia procumbens, Euphorbia rowlandii and Ceratheca saxicola are apparently restricted to sandy soil derived from Karoo sediments. Except for Euphorbia aeruginosa and the previously mentioned three plants all other endemic plants grow on soils derived from Soutpansberg quartzite.