**6. Phytogeographic comparison and biodiversity of Platberg**

The concept of islands having high numbers of endemics (MacArthur & Wilson 2001) associated; generally with low species richness (Linden 2003) is typical of island fauna and flora as well as African mountain regions (Kingdom 1989). Platberg, as an inselberg 'island' does not fully reflect this association; it has high numbers of endemics, 27 (Brand et al., 2010), but has high species richness with a total of 670 taxa.

On a global scale the United Kingdom (Whales, Scotland, Northern Ireland and England), covers 312 000 km² (a surface area four-orders-of-magnitude larger than Platberg which is 30 km²) with a total vascular plant species count of approximately 1400 of which none are endemic (Preston et al., 2002). In comparison Platberg has 670 species with the 27 endemic. It is problematic trying to compare species richness (alpha-diversity), with turnover between habitats (beta-diversity) and turnover between floras from one landscape to another (gamma-diversity), (Cowling et al., 1992). Similarities in edaphic conditions must take into account and environmental differences minimised to be able to match the differences in habitat gradients (Cowling et al*.*, 1992). For Platberg it is relatively easy to match alphadiversity with sites elsewhere. However, this becomes more problematic with beta and gamma diversity as different researcher use different plot sizes for similar biomes. For grassland Perkins et al., (1999a) uses 25² m, for Platberg plot size is 30 m² while Eckhardt et al. (1993, 1995), Fuls (1993) and Kay (1993) use 100 m² plot sizes.

Biogeography of Platberg, Eastern Free State, South Africa:

**Zimbabwe Inselbergs (Seine et al., 1998)** 

inselbergs (numbers represent species per family)**.** 

vegetation.

**Africa** 

**Platberg South** 

**(Brand et al., 2010)** 

5. Scrophulariaceae

28

Links with Afromontane Regions and South African Biomes 127

Cyperaceae (3 species), Poaceae (2), Orchidaceae (2) and Rubiaceae (2) with a total of only 15 species found on 100 relevés. For the *Selaginella caffrorum* mats on Platberg Poaceae was the most species rich family (9), second was Asteraceae (8), Cyperaceae with 4 and Crassulaceae with 3 species with a total of 100 species in 4 relevés giving an average of 25 species. Geophytes are abundant (6) with none occurring on the *Afrotrilepis pilosa* mats and few occurring on the Ivory Coast inselbergs. The high geophytes numbers is a trend seen in the DAC and an influence from the geophyte rich Cape flora (Goldblatt & Manning 2001). Porembski et al., (1996) found that on the vegetation of small size inselbergs in West African rain forests, 66 species of vascular plants occurred in 29 families, with the numbers showing good correlation with inselberg size. The largest Families are Poaceae, Cyperaceae, with Acanthaeceae, Commelinaceae and Malvaceae. Biogeographic affinities show species distribution widespread for Sudano-Zambezian elements, which are widespread for vegetation on inselbergs in the Comoé National Park in the Ivory Coast with Poaceae, Cyperaceae and Fabaceae comprising the most species rich families out of a total of 216 species found on 18 inselbergs (Porembski & Brown 1995); with most species found not being restricted to the inselbergs but in other habitats, savanna, marshes or waste ground. Inselbergs host a comparatively high amount of endemic species, 86 on Venezuelan inselbergs (Gröger & Barthlot 1996). Endemic angiosperms in the Drakensberg number 410, on Platberg, endemics number 27, three of which are Pterdophytes (Brand et al., 2010). Additionally, Table 6 shows a comparison of the most abundant inselberg family level

> **Ivory Coast Inselbergs Porembski et al.,**

Scrophulariaceae 22 Rubiaceae 22 Poaceae 31

**Venezuela Inselbergs** 

**1996)** 

**(Gröger & Barthlot** 

**1996)** 

1. Asteraceae 126 Poaceae 53 Poaceae 72 Cyperaceae 40 2. Poaceae 73 Cyperaceae 40 Cyperaceae 68 Rubiaceae 40 3. Cyperaceae 39 Fabaceae 40 Fabaceae 62 Melastomataceae 36 4. Fabaceae 33 Asteraceae 33 Scrophulariaceae 23 Orchidaceae 33

6. Hyacinthaceae 21 Euphorbiaceae 18 Orchidaceae 15 Bromeliaceae 20 7. Orchidaceae 16 Rubiaceae 18 Commelinaceae 14 Apocynaceae 18 8. Iridaceae 16 Lamiaceae 14 Lentibulaceae 14 Caesalpiniaceae 18 9. Geraniaceae 15 Adiantaceae 12 Caesalpiniaceae 13 Fabaceae 17 10. Crassulaceae 13 Acanthaceae 10 Euphorbiaceae 13 Euphorbiaceae 15 Table 6. A comparison of the 10 largest plant families for African and South American

It is obvious that some families have better representation on inselbergs than others. An immediate difference is Poaceae, which is fifth largest for Venezuela while it is first for the Ivory Coast and Zimbabwe, and second for Platberg and the DAC (Brand et al., 2010), with other species rich families of Cyperaceae, Asteraceae, Fabaceae, Scrophulariaceae and Orchidaceae. The trend for Platberg species rich flora is comparable to the DAC (Brand et al., 2010). The floristic trends shown on these disparate sites, all show high abundance for

Fig. 7. High altitude freshwater wetlands embedded in grassland on Platberg summit plateau.

Phytogeographic comparison for the vegetation of Platberg and Korannaberg is shown in Table 5 (Brand et al., 2010). There is a high degree of similarity for the Angiosperm flora for Platberg and Korannaberg with the larger numbers for Korannaberg possibly the result of the much larger area, (MacArthur & Wilson 2001, Cowling et al., 2002), which, as surface area increases, more species can be supported (Linder 2003, Gröger & Barthlott 1996). The higher species numbers for Korannaberg could be due to its position, which has strong Afromontane, Nana Karoo and Savanna Biome floristic influences (Du Preez & Bredenkamp 1991, Du Preez et al*.* 1991).


Table 5. A summary of Platberg and Korannaberg floras other sites, (modified from Brand et al., 2010)

However, climate and topography are only part of the explanation for high biodiversity and it is rather actual diversity of plant communities, which provides a measure of habitat diversity, (Cowling & Lombard 2002) and is a reflection of response to climate change (Scott et al., 1997; Mucina & Rutherford 2006).

For the Ivory Coast inselbergs, species composition was highest for Poaceae, then Cyperaceae, Scrophulariaceae and Lentibulariaceae. Species number and diversity were closely related to rainfall patterns for inselberg habitats (Porembski & Barthlott 1995). An examination of *Afrotrilepis pilosa* vegetation mats, shows the most species rich families are

Fig. 7. High altitude freshwater wetlands embedded in grassland on Platberg summit

Phytogeographic comparison for the vegetation of Platberg and Korannaberg is shown in Table 5 (Brand et al., 2010). There is a high degree of similarity for the Angiosperm flora for Platberg and Korannaberg with the larger numbers for Korannaberg possibly the result of the much larger area, (MacArthur & Wilson 2001, Cowling et al., 2002), which, as surface area increases, more species can be supported (Linder 2003, Gröger & Barthlott 1996). The higher species numbers for Korannaberg could be due to its position, which has strong Afromontane, Nana Karoo and Savanna Biome floristic influences (Du Preez & Bredenkamp

**Site Families Genera Species Area (km²)**  Platberg this survey 2007 96 305 670 30.0 Korannaberg (Du Preez 1991) 115 385 767 129.52

Table 5. A summary of Platberg and Korannaberg floras other sites, (modified from Brand et

However, climate and topography are only part of the explanation for high biodiversity and it is rather actual diversity of plant communities, which provides a measure of habitat diversity, (Cowling & Lombard 2002) and is a reflection of response to climate change (Scott

For the Ivory Coast inselbergs, species composition was highest for Poaceae, then Cyperaceae, Scrophulariaceae and Lentibulariaceae. Species number and diversity were closely related to rainfall patterns for inselberg habitats (Porembski & Barthlott 1995). An examination of *Afrotrilepis pilosa* vegetation mats, shows the most species rich families are

N/A N/A 566 47.9

> 76 > 229 481 494.30

73 176 263 5.244

plateau.

1991, Du Preez et al*.* 1991).

(Kay 1983)

al., 2010)

(Clever et al. 2005)

(Brown et al. 2005)

Golden Gate National Park

Kammanasie Nature Reserve

Bourke's Luck, Mpumalanga

et al., 1997; Mucina & Rutherford 2006).

Cyperaceae (3 species), Poaceae (2), Orchidaceae (2) and Rubiaceae (2) with a total of only 15 species found on 100 relevés. For the *Selaginella caffrorum* mats on Platberg Poaceae was the most species rich family (9), second was Asteraceae (8), Cyperaceae with 4 and Crassulaceae with 3 species with a total of 100 species in 4 relevés giving an average of 25 species. Geophytes are abundant (6) with none occurring on the *Afrotrilepis pilosa* mats and few occurring on the Ivory Coast inselbergs. The high geophytes numbers is a trend seen in the DAC and an influence from the geophyte rich Cape flora (Goldblatt & Manning 2001).

Porembski et al., (1996) found that on the vegetation of small size inselbergs in West African rain forests, 66 species of vascular plants occurred in 29 families, with the numbers showing good correlation with inselberg size. The largest Families are Poaceae, Cyperaceae, with Acanthaeceae, Commelinaceae and Malvaceae. Biogeographic affinities show species distribution widespread for Sudano-Zambezian elements, which are widespread for vegetation on inselbergs in the Comoé National Park in the Ivory Coast with Poaceae, Cyperaceae and Fabaceae comprising the most species rich families out of a total of 216 species found on 18 inselbergs (Porembski & Brown 1995); with most species found not being restricted to the inselbergs but in other habitats, savanna, marshes or waste ground.

Inselbergs host a comparatively high amount of endemic species, 86 on Venezuelan inselbergs (Gröger & Barthlot 1996). Endemic angiosperms in the Drakensberg number 410, on Platberg, endemics number 27, three of which are Pterdophytes (Brand et al., 2010). Additionally, Table 6 shows a comparison of the most abundant inselberg family level vegetation.


Table 6. A comparison of the 10 largest plant families for African and South American inselbergs (numbers represent species per family)**.** 

It is obvious that some families have better representation on inselbergs than others. An immediate difference is Poaceae, which is fifth largest for Venezuela while it is first for the Ivory Coast and Zimbabwe, and second for Platberg and the DAC (Brand et al., 2010), with other species rich families of Cyperaceae, Asteraceae, Fabaceae, Scrophulariaceae and Orchidaceae. The trend for Platberg species rich flora is comparable to the DAC (Brand et al., 2010). The floristic trends shown on these disparate sites, all show high abundance for

Biogeography of Platberg, Eastern Free State, South Africa:

Cowling & Lombard 2002).

**7.2.1 Birds** 

**7.2.2 Insects** 

association.

**7.2.3 Wind** 

**7.2 Pollination: Birds, insects and wind** 

needed to prevent the ecological specialisation from being lost…."

community associations and is a subject for future investigation.

Cape flora, on the Drakensberg and at Platberg.

Links with Afromontane Regions and South African Biomes 129

" … factors that allow (and drive?) speciation may be very similar to those that allow species to co-exist. These factors could be expected to include those that limit gene flow between sister species, as well as those that result in differential selection. Reproductive isolation is

This may offer a partial explanation for the high numbers of hybrids recorded, as well as the speciation and high numbers of endemics or near-endemics observed within the DAC and by extension, Platberg. Hybrids and rare species do not contribute to community patterns (beta-diversity), but are important for maintenance of biological diversity (Mutke et al. 2001;

For the central and southern Drakensberg, Hillard & Burtt (1987) have recorded bird pollination for *Protea, Kniphofia, Watsonia, Pelargonium schlecterii, Sutherlandea montana, Halleria lucida* and *Leonotis.* Most *Protea* species have a specalised feeding connection with Sugar birds *(Promerops* spp.) and Sunbirds (*Nectariania* species) detailed by Kingdom (1989) as well as the Cape Canary (*Serinus leucopterus*) and a beetle specialists which also feeds on Protea nectar. Except for *Protea*, all the other plant species occur on Platberg. This form of pollination, where a single pollinator will visit different, but close-by species with similar flower morphology and physiology, may also be responsible for the phytosociological associations of some plants. On Platberg, such community assemblage corresponds to the *Leonotis ocymifolia–Watsonia lepida* and *Halleria lucida* plant associations (Brand et al., 2009). Limited empirical research has been done to establish the connection between bird/plant

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

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

On Platberg, Asteraceae has the greatest numbers of genera and species, however grasses are the most dominant plant group with Cyperaceae the third most abundant. Wind dispersal is an important mechanism of pollination for grasses (Gibbs-Russell 1991) and for sedges (Gordon-Grey 1995). Wind pollination is also important for *Cliffortia* and *Anthospermum* fynbos species (Hillard & Burtt 1987), both of which are abundant on

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.

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