Boundaries

The Amatolo-Winterberg Highlands ecoregion covers a series of high-altitude Afromontane forests in the Eastern Cape Province of South Africa. It is situated on a relict arm of the Great Escarpment’s southern rim. To the south and east of the Amatolo-Winterberg Highlands lies the low-altitude coastal plain (Hughes & Hughes 1992). The headwater streams of this ecoregion are poorly studied, yet there is enough information to confirm that they host a rich aquatic fauna and a number of relict and endemic species.

Topography

The Amatolo-Winterberg Highlands extend south and east from the ranges of the Great Escarpment and are separated from the latter by the valleys of the Fish River in the west and the Great Kei to the north. The highlands represent a residual portion of the Great Escarpment that was bypassed by a more rapidly eroding Kei valley and retreating northern scarp (Wellington 1928 in Skelton 1986)(Skelton 1986a), such that it is an area where relict Afromontane fauna and flora have survived. The area tends to be rugged, with steep cliffs and valleys and several peaks around 2,000 m asl that rise from the low-lying rolling grasslands and valley bushveld. Sandy loam soils predominate.

Freshwater habitats

Streams of the Amatolo-Winterberg Highlands are both perennial and ephemeral but all are highly seasonal in their discharge. The streams are typically narrow, fast-flowing turbulent headwaters with rocky substrata, and many have sponges or bogs at their source and small areas of seasonally flooded marsh in flatter, low-altitude valleys (Hughes & Hughes 1992). 

Terrestrial habitats

A mixture of montane grasslands and fynbos heath is present at high altitudes, especially in rain-shadow areas. Below the montane grasslands the highlands and peaks are covered with both wet and dry Afromontane forest. Scrub forests and rolling grasslands replace these montane forests at lower altitudes. Riparian valleys tend to be thickly forested, and shorter, dry forest species are found on the steeper slopes and gorges. Dominant trees in the forest canopy include Rapanea, Podocarpus, Curtisia, Canthium, Celtis, Xymalos, Vepris, Ptaeroxylon,and Trichocladus. In the south, towards the Mpofu Game Reserve, the topography becomes gentler and rolling grasslands are more prevalent (Barnes 1998; Barnes et al. 2001).

Description of endemic fishes

The Eastern Province rocky (Sandelia bainsii), the border barb (Barbus trevelyani), and B. amatolicus are restricted to the tributaries of the Keiskamma and Buffalo Rivers in the Amatole Forest Complex (Mayekiso & Hecht 1988). In the 2002 IUCN Red List, Sandelia bainsii is listed as endangered and B. trevelyani is critically endangered (IUCN 2002). Both species are threatened by the presence of alien fish species and degradation and loss of habitat from excessive water abstraction.

Justification for delineation

This ecoregion is defined by the Amatolo-Winterberg Highlands and is the southern extent of the Montane-escarpment aquatic region (Skelton 1993). The fishes of the Amatolo-Winterberg Highlands belong to the temperate fish fauna of southern Africa. These species are only found in southern Africa between the coastal rivers and streams of the Cape and the southern plateau tributaries of the Limpopo River. Elements of both the “Cape” and “Karroid” fishes live in the waters of this ecoregion. Typical “Cape” fauna are those fish species found only in the Cape Fold Mountains and their outliers; the “Karroid” fishes are those inland species whose distribution closely follows that of the geological strata of the Karroo Sequence (Skelton 1986). As with the Drakensberg-Maloti Highlands [837], the presence here of a mixed fish fauna suggests that this ecoregion may prove to be a transition zone for other aquatic taxa as well.

Although the phylogenetics of the ecoregion’s “Cape” fishes (Sandelia bainsii and Barbus trevelyani) are too poorly understood to reveal the species’ biogeographic history, Skelton (1986) suggests that the distribution of the “Karroid” fishes (examples from the Amatolo-Winterberg Highlands include Labeo umbratus and Barbus anoplus) is intimately linked to the evolution of the Orange-Vaal River Basin. When the supercontinent Gondwanaland broke up, the continental margins of southern Africa warped upward (Corbett 1979, as cited in Skelton 1986). This resulted in the formation of two drainage systems: a huge system that drained the gently sloping land to the west of the escarpment (the Orange-Vaal River), and a much shorter, more powerful series of rivers that drained the eastern side. The Orange-Vaal system was more extensive during this time and drained much further north and south of its present catchment (Wellington 1958, as cited in Skelton 1986). As they received higher rainfall, however, and were eroding to a lower base level, the eastern systems gradually captured more and more of the peripheries of the inland drainage system. In the Amatolo-Winterberg Highlands, as in other places, fish species would have been “captured” from parts of the Orange-Vaal River and isolated in the new river systems. Here they underwent speciation, resulting in the formation of present-day endemics and range-restricted species (Skelton 1986).

Level of taxonomic exploration

Fair. There is surprisingly little information available on the wetland ecosystems of the Amatolo-Winterberg Highlands. Future research on aquatic taxa may reveal a rich and varied relict Afromontane fauna, in keeping with the results from the studies of fishes in the ecoregion.