Eastern Transvaal Escarpment Research Articles

Threatened fishes of the world: Chiloglanis emarginatus (Jubb & le Roux, 1969) (Mochokidae)

Common name: Phongolo rock catlet (E), Phongolo Suierbekkie (Afrikaans). Conservation status: Rare in South Africa (South African Red Data Book-Fishes, Skelton 1987), uncommon in Zimbabwe (Bell-Cross & Minshull 1988). Identification: Small (SL = 65 mm), scaleless catlet with depressed body. Disc-shaped mouth with relatively long mandibular barbels. Mandibular teeth long, up to 8 in number, widely space, width of band 25–40% width of inside of mouth. Dorsal fin with single unserrated spine. D I + 6, A III + 8. Caudal fin emarginate. Drawing by Penny Meakin. Distribution: Found in the eastern Transvaal escarpment sections of the Komati River (Incomati system) as well as the Ngwempisi, Hlelo, Assegaai and Phongolo rivers (Phongolo system) (Kleynhans 1986). C. emerginatus is also present in the Gwai, Lower Zambezi and Pungwe rivers in Zimbabwe (Bell-Cross & Minshull 1988). Abundance: Constitutes on average 5.5% of the total catch with a frequency of occurrence of 58.8% in its preferred habitat in the Incomati system. It is more common in the Phongolo system, constituting 12.1% of the total catch and having a frequency of occurrence of 75.9%. Habitat and ecology: Occurs at an altitude of 900–1200 m above sea level. This catlet has a preference for flowing water in runs, riffles and rapids (flow speed = 0.18–0.70 m sec, width = 2–5 m, depth = 0.2–0.4 m (Kleynhans 1984). The mouth is used as a sucking disc to maintain its position in fast-flowing water. The gut length is less than the standard length and the mandibular teeth are used to scrape invertebrates from stones. Feeds on epilithic aufwuchs and small stream invertebrates, especially insect larvae, ostracods and small molluscs. Co-exists with minnows (Barbus species), yellowfishes (Barbus polylepis, B. marequensis, Varicorhinus nelspruitensis) and labeos (Labeo cylindricus and L. molybdinus), the mountain catlet Amphilius uranoscopus and other Chiloglanis species. Natural enemies may include longfin eels Anguilla mossambica. Reproduction: The Phongolo rock catlet is a serial spawner that breeds from October to April and produces a maximum of about 320 ova per season (Kleynhans 1984). It is likely to be an interstitial gravel spawner like the related Chiloglanis pretoriae (de Villiers & Hecht 1991). Threats: Fragmentation of populations, habitat alteration and flow regulation due to the construction of impoundments in both the Phongolo and Incomati systems constitute the greatest threats (Kleynhans 1984). The envisaged increase in the catchment area planted with exotic tree plantations may in future decrease water runoff and water quality in this catlet’s habitat. Water abstraction for agriculture and industrial usage may also cause habitat alterations. Conservation action: Monitoring of the population numbers of this catlet and its habitat is undertaken on a regular basis by the conservation authorities. Conservation recommendations: The minimum flow requirements for the survival of this species must be determined as it is subject to flow regulation and reductions in runoff. The conservation status in Zimbabwe should be determined. Remarks: C. emarginatus is one of several species of fishes inhabiting fast-flowing rivers in southern Africa which have restricted distributions and are threatened with extinction by habitat alterations.

Genetic relationships between Marico barb (Barbus motebensis, Steindacher 1894), Redtail barb (B. gurneyi, Günther 1868) and Amatola barb (B. amatolicus, Skelton 1990)

SummaryStarch gel‐electrophoresis was used to assess genetic differences between two populations of Barbus motebensis and two other taxonomic related and morphologically similar barb species. Ten of the 29 protein coding loci studied were polymorphic. In spite of the small bio‐metric and meristic differences between the species studied, the extent of genetic differences suggests four distinct species. The evidence in support of a new barb species in the Ohrigstad River further adds to the current conservation importance of the rivers of the eastern Transvaal escarpment as a ‘hotspot’ for endemic fish species.

The phytosociology and syntaxonomy of relatively low-altitude areas in the North-eastern Mountain Sourveld, in the eastern Transvaal escarpment region

An analysis of the vegetation of the relatively low altitude regions of the North-eastern Mountain Sourveld of the eastern Transvaal escarpment is presented. Releves were compiled in 53 stratified random sample plots. ATWINSPAN-classification, refined by Braun-Blanquet procedures, revealed seven plant communities. In the hierarchical classification one class, one alliance, four associations, four subassociations and two valiants are recognised. Formal syntaxonomic descriptions of the syntaxa are given. All communities are related to specific environmental conditions, of which geology, aspect, altitude and rockiness of the soil surface are the most important.

A new species of Haemanthus (Amaryllidaceae) from the eastern Transvaal Escarpment, South Africa

Two disjunct populations of Haemanthus L., recently discovered in the Blyderivierspoort Nature Reserve and near Barberton, are morphologically distinct from previously described species. This new species, H. pauculifolius Snijman & Van Wyk, is most closely allied to H. albiflos Jacq. from which it differs by its mostly solitary leaf, smaller compact umbel and longer flowers. Twee disjunkte bevolkings van Haemanthus L., wat morfologies van die reeds bekende spesies verskil, is onlangs in die Blyderivierspoortnatuurreservaat en naby Barberton ontdek. Die nuwe species, H. pauculifolius Snijman & Van Wyk, is verwant aan H. albiflos Jacq., maar verskil daarvan in die hoofsaaklik enkele blaar, die kleiner kompakte skerm en die langer blomme.

Ordination as a tool for substantiating and interpreting floristic classifications: a case study

Detrended Correspondence Analysis ordination is used as a tool for substantiating the authenticity of hierarchical syntaxa derived from a phytosociological classification of the vegetation of the Eastern Transvaal Escarpment in the Sabie area. Ecological interpretation of syntaxa is facilitated by superimposing environmental variables on axes of ordination.

The vegetation ecology of the Eastern Transvaal Escarpment in the Sabie area. 1. Physical environment

The physiography, geology, soil and climate of a broad transect of the Eastern Transvaal Escarpment in the Sabie area are described. The transect extends from Hazyview (530 m elevation) to Mount Anderson (2 280 m elevation). The description provides a contextual framework for the subsequent vegetation classification.

The vegetation ecology of the Eastern Transvaal Escarpment in the Sabie area. 3. Annotated checklist

Over 1 000 plant taxa occumng in a 1 300 km; belt transect extending from Hazyview (530 m elevation) to Mount Anderson (2 280 m elevation) in the Sabie area of the Eastern Transvaal Escarpment are listed by genus, with species arranged alphabetically within genera. Annotations include genus author, species author, growth form, habitat, collector and specimen number Floristic analysis shows the Asteraceae as representing the largest family, followed by the Fabaceae. Poaceae. Rubiaceae and Liliaceae Flonstic affinities are briefly discussed.

The vegetation ecology of the Eastern Transvaal Escarpment in the Sabie area. 2. Floristic classification

The indigenous vegetation of the Eastern Transvaal Escarpment in the Sabie area is classified with the aid of the PHYTOTAB program package. Four ecological-formation classes (efc) based on floristics. physiognomy and climate correspond to four data subsets. Plant communities in each efc are defined by means of 46 differential species-groups distributed amongst forest, thicket, woodland, shrubland and grassland structural types. Environmental correlation is facilitated by means of 21 habitat types.

Weathering Sequence and Alteration Products in the Genesis of the Graskop Manganese Residua, Republic of South Africa

AbstractAlthough numerous, small, manganese oxide deposits associated with dolomite in the Eastern Transvaal escarpment, Republic of South Africa, have been known for many years, their mineralogical make-up is somewhat controversial. Chemical, mineralogical, and morphological properties of the weathering products of dolomite and the coexisting manganese oxide material in the Graskop area were therefore determined. Mn and Fe occur only in minor accessory minerals in the original rock; however, in the weathering residue, these elements are concentrated and occur as separate mineral phases, chiefly birnessite, nsutite, and goethite. Thin veins of pure muscovite and quartz traverse the residua. Rare, pure calcite and maghemite nodules were noted throughout the residual manganese material. The properties of this weathering sequence suggest that the manganese wad deposits were formed in situ as a result of the congruent dissolution of dolomite, leaving a porous, sponge-like structure, highly enriched in Mn and Fe oxides.

ASPECTS OF THE ECOLOGY OFKNERIA AURICULATA(PELLEGRIN, 1905) (PISCES: KNERIIDAE) FROM THE EASTERN TRANSVAAL SOUTH AFRICA

SUMMARY Seven natural populations of Kneria auriculata occur in tributaries of the Crocodile River (Incomati System) on the eastern Transvaal escarpment. The routes it probably used to colonize these streams are discussed and used to explain its current restricted distribution with reference to its ecological requirements. Fish up to a fork length of 2,0 cm feed on invertebrates while larger fish utilize ‘Aufwuchs’, especially diatoms. This dietary difference results in an increase in the food spectrum and possibly also serves to limit competition between smaller and larger lengths groups. Relative gut lengths increase with an increase in fork length and this is correlated with a change in diet from invertebrates to diatoms. Observations on captive fishes indicated that adult fish are able to survive on a diet of Daphnia spp. The habitat of K. auriculata is considered to be unstable due to the occurrence of unpredictable summer floods in escarpment streams. As a result the species has a prolonged breeding season (October to April) while the presence of two size classes of ova indicate that it is a multiple spawner. This breeding strategy minimizes mortality in escarpment streams. The colonization by this fish of previously unsuitable and unavailable habitat indicates that it is a generalist. Its feeding habits and reproductive strategy indicate, however, that it has developed a certain degree of specialization in order to survive in a relatively unpredictable habitat. The conservation prospects of the seven natural and one translocated population varies from uncertain to good. Medium and long term conservation measures are needed to ensure the survival of this fish in the Transvaal.

The effect of afforestation with Eucalyptus grandis Hill ex Maiden and Pinus patula Schlecht. et Cham. on streamflow from experimental catchments at Mokobulaan, Transvaal

This paper reports results of a catchment experiment on the Eastern Transvaal escarpment, South Africa. Gauging of flow from the catchments under natural grass cover began in 1956. One of the catchments was planted to Eucalyptus grandis in 1969 after 12 years of calibration, a second was planted to Pinus patula in 1971, and the third was maintained in the natural condition. Simple regression analysis procedures were used and showed that afforestation with Eucalyptus grandis exerted an observable influence from the third year after planting, with a maximum apparent reduction in flow, expressed as rainfall equivalent, of between 300 and 380 mm yr. −1, and with maximum reductions in seasonal flow of about 200–260 mm yr. −1 in summer and 100–130 mm yr. −1 in winter. Conclusions from the Pinus patula treatment are very tentative, but the effect of afforestation is apparently delayed by one year relative to that of Eucalyptus grandis, and apparent streamflow reductions are smaller.

The influence of temperature on the life-cycle and distribution of Biomphalaria pfeifferi (Krauss, 1948) in South-Eastern Africa

An annual life-cycle of three over-lapping generations was found for Biomphalaria pfeifferi in a perennial stream on the eastern Transvaal escarpment. The 2nd of these generations appeared during the hottest months of the year—late January and February. This generation sequence was confirmed in a completely different environment, a permanent pond in a climatically different area, the coastal peneplain of north-eastern Zululand though the density of the 2nd generation here was much reduced. The species is moreover absent from certain types of shallow, permanent waterbody (pans) on this plain. In these habitats the thermal regime rose above those in other types during spring and early summer—the maturation period of the 1st generation. A negative partial-correlation, significant at a 1% level, was found between decreasing fecundity of the 1st generation and increasing periods of above-optimal temperatures (> 27°C) during its maturation period. This temperature effect accounts for the species' absence from pans in the area and the critical duration of these above-optimal temperatures appears to lie between mean weekly levels of 120 and 179 deg.h. > 27°C. The discontinuous distribution of B. pfeifferi in the Lake Sibaya area of the Zululand coastal plain corresponds to an ecological succession amongst waterbodies associated with the lake's fluctuating water level. The separation of sheltered bays from the lake was followed by further lowering of their levels and a spread of emergent vegetation. This is believed to have contributed to an increasingly high thermal regime, especially during spring when temperatures rise rapidly. The pans from which B. pfeifferi is absent constitute the present end point of this succession.