Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: The Greater Cederberg Biodiversity Corridor (GCBC) is a large-scale conservation
corridor situated in the south-western region of South Africa. Delineation of the GCBC
was largely based on by vegetation data. The relevance of the GCBC for the
conservation of the reptilian fauna in the area south of 31°S and west of 21°E is assessed
in the present study. This entailed determining the GCBC’s coverage of regional reptile
diversity patterns and assessing its potential conservation significance during possible
climate induced changes in reptile distributions.
Reptile species point distribution data from the preliminary (2007) SARCA (South African
Reptile Conservation Assessment) database was used. Under-representation of the
Tankwa Karoo in the dataset required a field survey of this region. Additionally, the
biogeographical influence of the arid Tankwa Karoo Basin on the distribution of reptiles in
the south-western districts of South Africa was investigated. Turnover across the Basin is
high, species richness is lower than in surrounding mountainous areas and there are no
species endemic to the area. The Tankwa Karoo Basin acts as a dispersal barrier for
many reptile species occurring in the surrounding more mesic areas. At the same time,
the ranges of a number of typical northern, arid adapted species extend southward along
the Tankwa Plains. A number of species range extensions in the region are reported.
Patterns of endemism, species richness and turnover were plotted from the point
distribution data at quarter and eighth degree square resolution. Extensive sampling bias
towards reserves and populated areas is apparent from the reptile species richness plots.
This pattern is more pronounced for snakes than lizards. Reptile richness is particularly
high along the north-south section of the Cape Fold Mountains and also relatively high
along the south-western coast, peaking in the Lambert’s Bay area. The majority of the 20
reptile species endemic to the study area are associated with one of two identified centres of endemism: the Greater Cederberg area, or the narrow coastal zone stretching from the
Lambert’s Bay area to the Cape Peninsula. An additional third set of endemics comprised
of melanistic forms restricted to a number of different refugia, notably, Landroskop, the
Cape Peninsula, Sladanha-Langebaan region, Piketberg Mountains and a confined area
along the western section of the Cape Fold Mountains. Species richness and endemism
patterns co-vary within the study area.
Biotic regions were identified through hierarchical clustering of grid cells according to
shared species occurrences. A Northern, Southern, Central and Western biotic region
was identified. Classification tree methodology (CART) and Canonical Correspondence
Analysis (CCA) were used to characterise defined biotic regions in terms of selected
environmental variables. Four sets of species assemblages are described on the basis of
these biotic regions – two major and two minor ones. Of the major assemblages the
Northern assemblage can be described as an arid zone one and the Southern
assemblage as a mesic zone one. The minor Central assemblage, comprising mainly
rock-dwelling forms, represent evolutionary leftovers as a result of climate change induces
cycles of contraction and expansion of arid and mesic faunas. The other minor one, the
West Coast assemblage could be considered a sub-assemblage of the Northern one, with
particular adaptation to the coastal climate. Environmental characterisation of the biotic
regions reveals that these groupings are supported by an environmental signal. The
contiguity of four distinct sets of reptiles, each with its own set of environmental
requirements, in this relatively small geographic area clearly indicates that the southwestern
region of South Africa is biogeographically complex.
The GCBC incorporates the largely coinciding centres of endemism and richness along
the West Coast and the greater Cederberg area. Although the centre of endemism for
melanistic reptile forms, in the Saldanha-Langebaan area, falls just south of the GCBC
boundary, the Corridor fulfils the requirements for effective conservation of reptiles in the area to a large degree. The north-south dispersal pathways provided by the Corridor
along the Cape Fold Mountains is believed to be adequate to buffer climate change
effects, however there is concern about its ability to contribute to the persistence of the
assemblage associated with the narrow coastal zone in the west. / AFRIKAANSE OPSOMMING: Die Groter Cederberg Biodiversiteit Korridor (GCBK) is ‘n grootskaalse bewaringskorridor
wat in die suid-westelike deel van Suid-Afrika geleë is. Die grense van GCBK is
gebasseer op plantegroei data. In die huidige studie word die betekenis van die GCBK vir
die bewaring van die reptiel fauna in die gebied suid van 31°S en wes van 21°O
assesseer. Die mate waartoe die GCBK die patrone van reptieldiversiteit in die streek
inkorporeer, asook die korridor se potensiaal om voorsiening te maak vir reptiel
verspreidingsgebiede wat moontlik as gevolg van potensiële omgewingsverandering kan
verskuif.
Die beskikbare puntverspreidingsdata van die voorlopige (2007) SARCA (South African
Reptile Conservation Assessment) databasis is gebruik. Swak verteenwoordiging van die
Tankwa Karoo in die datastel het ‘n veldopname van die gebied genoodsaak. Verder is
die biogeografiese invloed van die ariede Tankwa Karoo Kom op die verspreidingspatrone
van reptiele in die suid-westelike deel van Suid-Afrika ook ondersoek. Die spesie omset
van beide Noord na Suid en Wes na Oos oor die Tankwa is hoog, die spesierykheid is
aansienlik laer as in die omringende bergagtige gebiede en daar is geen spesies wat
endemies is tot die Tankwa Karoo nie. Die Tankwa Karoo Kom dien as ‘n barieêre teen
spreiding vir sommige reptielspesies wat in die omringende gematigde gebiede voorkom.
Terselfdertyd reik die verspreidings van ‘n aantal tipiese droogte aangepasde spesies
vanuit die noorde suidwaarts langs die Tankwa Vlaktes. Nuwe verspredingsrekords wat
‘n paar spesies se gebiede uitbrei word ook raporteer.
Die puntverspreidingsdata is geruik om die patrone van endemisme, spesierykheid en
omset op kwart- en agtstegraad resolusie te plot. Spesierykheid kaarte toon ‘n duidelike
neiging tot deegliker opnames in reservate en bewoonde gebiede. Hierdie patroon is meer opmerklik vir slange as akkedisse. Reptielrykheid is besonders hoog langs die
noord-suid as van die Kaapse Plooiberge en ook relatief hoog langs die suid-wes kus met
‘n maksimum in die Lambertsbaai omgewing. Die meerderheid van die 20 reptielspesies
wat endemies is aan die studie area is met een van twee geïdentifiseerde sentrums van
endemisme geassosieer: die Groter Cederberg area óf die nou kussone wat vanaf
Lambertsbaai tot Kaappunt strek. ‘n Derde stel endemiese spesies wat uit melanistiese
vorme bestaan, is beperk tot ‘n aantal refugia, naamlik, Landroskop, Kaappunt, Saldanha-
Langebaan omgewing, Piketberg berge en ‘n beperkte area langs die westelike dele van
die Kaapse Plooiberge. Spesierykheid en endemisme patrone stem grootliks ooreen
binne die studie area.
Roosterselle is op grond van gedeelde spesiesamestellings met behulp van ‘n hieragiese
groeperingsmetode (Incremental Sum of Squares) gegroepeer. Vier bio-areas, nl. ‘n
Noordelike-, Suidelike-, Sentrale en Westelike bio-area is identifiseer. Klassifikasieboom
metodologie (Classification and Regression Trees, CART) asook Kanoniese Annalises
(Cannonical Correspondence Annalysis, CCA) is gebruik om hierdie geografiese areas in
terme van ‘n aantal omgewingsveranderlikes te karakteriseer. Vier spesieversamelings,
twee groter en twee kleiner versamelings, is in ooreenstemming met hierdie vier areas
geïdentifiseer. Die Noordelike en Suidelike spesieversamelings is die groteres en kan
beskryf word as die faunas van onderskeidelik ‘n ariede en gematigde sone. Die kleiner
Sentrale versameling bestaan hoofsaaklik uit rots-lewende spesies en mag die
evolusionêre oorblyfsels verteenwoordig van ariede en gematigde faunas waarvan die
verspreidings herhaaldelik as gevolg van klimaatsveranderingsiklusse uitgebrei en
gekrimp het. Die Weskus versameling is ook ‘n kleiner een en kan as ‘n sub-versameling
van die Noordelike een beskou word, maar spesifiek tot die kus klimaat aangepas. Die
klassifikasie van hierdie bio-areas word ondersteun deur die analiese van die
omgewingsveranderlikes. Die feit dat vier kenmerkende versamelings reptiele, elk met sy besondere omgewingsvereistes, in hierdie relatief klein geografiese area ontmoet, dui
daarop dat die suid-westelike deel van Suid-Afrika biogeografies kompleks is.
Die GCBK inkorporeer die grootliks ooreenstemmende sentrums van endemisme en
rykheid wat langs die Weskus en in die groter Cederberg area voorkom. Alhoewel die
sentrum van melanistiese endemiese spesies, in die Saldanha-Langebaan omgewing, net
buite die grense van die Korridor val, voldoen die GCBK grootliks aan die vereistes vir die
effektiewe bewaring van reptiele in die gebied. Die voorsiening van noord-suid
verspreidingsweë langs die Kaapse Plooiberge binne die Korridor word beskou as
voldoende om die gevolge van klimaatsverandering te buffer. Daarinteen is daar kommer
oor die vermoeë van die GCKB om ‘n doeltreffende bydrae te maak tot die voortbestaan
van die spesieversameling wat met die nou kussone langs die Weskus geassosieer is.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21676 |
| Date | 03 1900 |
| Creators | Meyer, Anita |
| Contributors | Mouton, P. le F. N., Mucina, L., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiii, 140 leaves : ill. |
| Rights | Stellenbosch University |
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