**7.2.2 Insects**

128 Biodiversity Loss in a Changing Planet

Asteraceae, Poaceae and Fabaceae which may represent the pattern of evolutionary radiation seen for these groups during the Eocene as well as associated ungulate grazers and predatory fauna (Retallack 2001). Cyperaceae is another important group, and its exploitation of environmental niches and evolution, may be parallel with Grasses, but may show a some-what different route. Cyperaceae are a widespread family, but generally have a lesser cover abundance throughout their range compared with grasses (Du Preez & Bredenkamp 1991; Kooij 1990; Perkins et al., 1999a; Bester 1998). Cyperaceae (like Poaceae) seems to have evolved C4 photosynthetic pathways several times (Clayton 1975; Ferrier 2002; Stock et al., 2004) and even though they form components of grasslands and are commonly associated with wetlands and other seasonally moist areas, they also occur in arid regions (Gordon-Grey 1995; Jürgens 1997; Stock et al., 2004). Unlike Grasses (Gibbs-Russell et al., 1991) for Cyperaceae in southern Africa, no strong relationship is found such as altitude and rainfall (Stock et al., 2004). Their development may be less dependent on the mechanisms responsible for grass radiation, it may be that co-evolution of grasses and ungulates, climate change and CO2 level changes, is a reflection of composition found in the DAC, Platberg and the inselbergs compared in Table 3, which show a general pattern for the

top most specious families to include Asteraceae, Poaceae, Cyperaceae and Fabaceae.

Mucina & Rutherford 2006) where high levels of endemic species (63.2%) are found.

**7. Factors influencing inselberg flora** 

**7.1 Hybridisation** 

flow (Linden 2003).

For Venezuela inselberg flora, Asteraceae is significantly under represented which is a reflection of the South American regional flora, which occurs in high rainfall areas (Gröger & Barthlot 1996). This is the same trend shown for Ivory Coast inselbergs, moisture availability is the common environmental factor (Gröger & Barthlot 1996). Asteraceae is not well represented in west Africa, unlike East Africa where in Zimbabwe, the DAC and Platberg significant high levels of Asteraceae are found. This trend is representative of the Asteraceae for arid and semi-arid regions, including the CFR (Jürgens 1997; Linder 2003,

For the DAC, Hillard and Burtt (1987) list 21 hybrid taxa of which three (two *Senecio* crossed species and one *Cephalaria*) are exclusive to high altitude DAC records, and do not occur on Platberg, while the *Protea roupelliae* x *P. subvestita* cross has both species growing in the vicinity of Platberg. Of the remaining 17 hybrids it could be that some or all of them may occur on Platberg. This level of taxonomic expertise must wait for future detailed analysis. Hillard & Burtt (1987) do not offer an explanation for the occurrence of these 21-recorded hybrids (it is possible there are more). However, hybridisation breaks down species boundaries. Linden (2003) reports for the Cape flora, where species co-occur, such as *Moraea* hybrids, these are frequently found. This is the case also for *Romulea* with artificial hybrids cultivated for *Sparaxis, Watsonia* and *Ixia* of which *Watsonia* and *Morea* occur on Platberg (Linden 2003). Most of these Cape hybrids are sterile, however, hybridisation, sterile or not, is an environmental response to selection forces, which, in the case of Cape flora, limit gene

For the higher areas of the DAC, and Platberg as an inselberg, a degree of geographical isolation occurs which allows for edaphic and microclimatic, as well as larger, longer climatic and geological processes, to provide for geographical isolation of species (MacArthur & Wilson 2001; Porembski & Brown 1995; Gröger & Barthlott 1996; Linden 2003). This isolation has allowed for speciation and to quote from Linden (2003, page 623): Hillard and Burtt (1987) have also described pollination by bees of highly specalised plants; Orchidaceae, and Scrophulariaceae. In the Fynbos Biome closely related plant species could have very different pollinators, with pollinator selection playing a central role in speciation and species richness (Linden 2003). Hillard & Burtt (1987) and Linden (2003) discuss the possible link between insect pollinators and floral guilds (phytosociological communities), with the possibility that such guilds are the results of insect/plant interaction and association.

Orchidaceae is a species rich family in the Cape flora and comprise 3.3% of the entire flora (Goldblatt & Manning 2000), 5.2% of the angiosperm DAC flora (Carbutt & Edwards 2004) and 2.7% of Platberg flora. Many orchid species are unique to select habitats. It may be that the process of pollination as well as pollinator selection (Hillard & Burtt 1987, Linden 2003) may play a significant part in accounting for the high numbers of Orchidaceae found in the Cape flora, on the Drakensberg and at Platberg.
