**1. Introduction**

112 Biodiversity Loss in a Changing Planet

Weiner, S. & Dove, P. (2003). An overview of biomineralization processes and the problem

Weisz, J.B.; Massaro, A.J.; Ramsby, B.D. & Hill, M. (2010). Zooxanthellar symbionts shape

Weisz, J.H.; Lindquist, N. & Martens, C.S. (2008). Do associated microbial abundances

Welsh, D.T.; Viaroli, P.; Hamilton, W.D. & Lenton, T.M. (1999). Is DMSP synthesis in

Wild, C.; Huettel, M.; Klueter,A.; Kremb, S.; Rasheed, M.Y.M. & Jorgensen B.B. (2004). Coral

Wild C., Rasheed M., Jantzen C., Cook P., Struck U., Huettel M. & Boetius A. (2005). Benthic

Wild, C.; Hoegh-Guldberg, O.; Naumann, M.S.; Colombo-Pallotta, F.; Ateweberhan, M. et al.

abalone *Haliotis asinine. Biol. Bull.*, Vol.215, pp. 98-107, ISSN: 0006-3185 Wong, K.K.W.; Lane, A.C.; Leung, P.T.W. & Thiyagarajan, V. (2011, in press). Response of

Woolard, F.X.; Moore, R.E. & Roller, P.P. (1979). Halogenated acetic and acrylic acids from

Woods Hole Oceanographic Institute: http://www.whoi.edu/OCB-OA/FAQs/)

Dove, P.M., DeYoreo, J.J. and Weiner, S. Vol. 54, pp. 1-29

189–197, ISSN*:* 0006-3185

ISSN*:* 0171-8630

ISSN: 0031-9422

pp. 367-376, ISSN: 0029-8549

Vol.11, pp. 265-278, ISSN: 0394-9370

*Physiol. Part D,* 12 pages, in press.

*Nature*, Vol.428, pp. 66-70, ISNN: 0028-0836

of vital effect. In: Biomineralization. Reviews in Mineralogy & Geochemistry. Eds.

host sponge trophic status through translocation of carbon. *Biol. Bull.*, Vol.219, pp.

impact marine demosponge pumping rates and tissue densities? *Oecologia*, Vol.155,

chlorophycean macro-algae linked to aerial dispersal? *Ethology Ecology & Evolution,*

mucus functions as an energy carrier and particle trap in the reef ecosystem.

metabolism and degradation of natural particulate organic matter in carbonate and silicate reef sands of the northern Red Sea. *Mar. Ecol. Prog. Ser.*, Vol. 298, pp. 69–78,

(2011). Climate changes impede scleractinian corals as primary reef ecosystem engineers. *Marine and Freshwater Research*, Vol.62, pp. 205–215, ISSN*:* 1323-1650 Williams, E.A.; Craigie, A; Yates, A. & Degnan, S.M. (2008). Articulated coralline algae of the

genus *Amphiroa* are highly effective natural inducers of settlement in the tropical

larval barnacle proteome to CO2-driven seawater acidification. *Comp. Biochem.* 

the red alga *Asparagopsis taxiformis Phytochemistry* 18 (4), Vol.18, No4, pp. 617-620,

This chapter comprises a vegetation analysis of Platberg, eastern Free State, South Africa (Figure 1). Platberg is an inselberg which has high botanical diversity, with associated species richness, and high numbers of endemic taxa only found at high altitudes over 2 000 m.a.s.l. indicative of montain flora.

Inselbergs are one of the most striking and persistent landform types in Africa (Goudie 1996) and are defined as an isolated hill, knob, koppie or small mountain, which stands alone and rises abruptly, island-like, from the surrounding terrain (Sarthou & Villiers 1998). In the eastern Free State, South Africa, rising abruptly from the flat terrain of the Karoo sediments, are a series of more than 20 prominent inselbergs all over 2000 m high. These flat-topped, steep-sided inselbergs stretch north from the Qwa-Qwa scarp, which constitutes the northern endpoint of the Maluti-Drakensberg. Geologically, these inselbergs are an extension of the Maluti Drakensberg, and occur along a line prescribed by the Great Escarpment (King 1963) at 1800 m. They form a discrete island-like archipelago stretching over 200 km, connecting the main Lesotho-Maluti-Drakensberg with the Mpumalanga-Drakensberg, and the Highveld Mountains to the north.

Inselbergs are formed from igneous or sedimentary rocks, capped by more resistant strata. The remnants of the resistant igneous capping form the distinct flat-topped mesas, buttes or table mountains. Platberg (Figure 2) and all the other inselbergs are the structurally controlled remnants of such weathering processes (King 1963; Moon & Dardis 1992). As prominent landscape features, geomorhologically they are formed by extensive subsurface decay along joints. The subsequently loosened material is removed by water, wind and gravity, with thawing and freezing assisting the process (Moon & Dardis 1992). The accompanying erosional detritus, rocks, boulders and gravel, form the steep slopes to the inselbergs, which are slowly buried in the rock debris (Figure 3). It is the packing of this weathered material, which provides the numerous ecological niches for the development of biodiverse plant communities characterised by inselbergs (Sarthou & Villiers 1998).

The unique, high altitude conditions found above 2 000 m, lead to high levels of endemism in organisms; bryophytes, plants and animals (Hillard & Burtt 1987; Van Wyk & Smith 2001; Carbutt & Edwards 2006; Mucina & Rutherford 2006). This is due to the compression of

Biogeography of Platberg, Eastern Free State, South Africa:

feature of Platberg.

inselbergs and the Afromontane region.

**1.1 African phytochoria and species richness** 

Links with Afromontane Regions and South African Biomes 115

shows strong floristic and plant community similarities with Gd 8 Lesotho Highland Basalt Grassland, and demonstrates Platberg is an extension of the same phytochoria as the DAC.

Fig. 2. The contact between the dark dolerite cap and the lighter sandstone is a distinct

Fig. 3. Mobile boulder beds on Platberg provide habitat for species and vegetation unique to

The phytochoria of Africa have been formally classified by White (1983), who defined eighteen major phytochoria for Africa. The two phytochoria of interest for this work as are the *Afromontane* archipelago-like regional centre of endemism (VIII), and embedded within the *Afromontane* phytochoria is the *Afroalpine* archipelago-like centre of extreme floristic impoverishment (IX). The basis of White's work was to produce a vegetation map for Africa, using two criteria: the physiognomy of the most extensive vegetation type, and floristic composition. This produced a useful, broad scale map of regional biodiversity, but did not

have the resolution to show species richness on the local or community level.

climatic life zones over a short distance that makes mountains hot spots for biological diversity (Körner 2003). Inselbergs may be regarded as analogous with an archipelago of islands in an 'ocean' of low-level vegetation types which act as an isolation factor (Taylor 1996; MacArthur & Wilson 2001).

Fig. 1. Platberg, Eastern Free State, South Africa (Brand 2008).

This in turn precludes plant species with less mobile seed dispersal mechanisms from propagating over wide ranges, and allows for high levels of endemism to develop (Taylor 1996). High levels of endemism mean that a large proportion of the available gene pool is unique to that site, and inselbergs and mountains therefore have an important role to play in the maintenance of genetic diversity (Taylor 1996; Mucina & Rutherford 2006).

Inselbergs are differentiated from their surroundings by harsher edaphic and microclimatic conditions (Porembski & Barthlott 1995), consequently they host distinctive species, forming unique phytosociological associations, which differ from the lowland vegetation matrix in which they are embedded (Porembski & Brown 1995; Porembski et al., 1996, 1997, 1998; Sarthou & Villiers 1998; Parmentier et al., 2006). The vegetation map of Mucina & Rutherford (2006) shows Platberg as an inselberg embedded in the lowland grassland but also as a high altitude vegetation unit designated as the Gd 8 Lesotho Highland Basalt Grassland, part of the Drakensberg Grasslands predominantly associated with the broader Drakensberg Alpine Centre (DAC). Prior to this study no field data was available to prove this hypothesis. These studies provides empirical data on a detailed vegetation level that

climatic life zones over a short distance that makes mountains hot spots for biological diversity (Körner 2003). Inselbergs may be regarded as analogous with an archipelago of islands in an 'ocean' of low-level vegetation types which act as an isolation factor (Taylor

1996; MacArthur & Wilson 2001).

Fig. 1. Platberg, Eastern Free State, South Africa (Brand 2008).

This in turn precludes plant species with less mobile seed dispersal mechanisms from propagating over wide ranges, and allows for high levels of endemism to develop (Taylor 1996). High levels of endemism mean that a large proportion of the available gene pool is unique to that site, and inselbergs and mountains therefore have an important role to play in

Inselbergs are differentiated from their surroundings by harsher edaphic and microclimatic conditions (Porembski & Barthlott 1995), consequently they host distinctive species, forming unique phytosociological associations, which differ from the lowland vegetation matrix in which they are embedded (Porembski & Brown 1995; Porembski et al., 1996, 1997, 1998; Sarthou & Villiers 1998; Parmentier et al., 2006). The vegetation map of Mucina & Rutherford (2006) shows Platberg as an inselberg embedded in the lowland grassland but also as a high altitude vegetation unit designated as the Gd 8 Lesotho Highland Basalt Grassland, part of the Drakensberg Grasslands predominantly associated with the broader Drakensberg Alpine Centre (DAC). Prior to this study no field data was available to prove this hypothesis. These studies provides empirical data on a detailed vegetation level that

the maintenance of genetic diversity (Taylor 1996; Mucina & Rutherford 2006).

shows strong floristic and plant community similarities with Gd 8 Lesotho Highland Basalt Grassland, and demonstrates Platberg is an extension of the same phytochoria as the DAC.

Fig. 2. The contact between the dark dolerite cap and the lighter sandstone is a distinct feature of Platberg.

Fig. 3. Mobile boulder beds on Platberg provide habitat for species and vegetation unique to inselbergs and the Afromontane region.
