Dissertation (PhD)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: South Africa, Lesotho and Swaziland are home to an endemic group of dwarf
chameleons (Bradypodion). They are small, viviparous, insectivorous, arboreal
lizards, found in a variety of vegetation types and climatic conditions. Previous
work on Bradypodion pumilum suggests prolonged breeding and high fecundity
which is very unusual for a viviparous lizard inhabiting a Mediterranean
environment. It has been suggested that the alleged prolonged reproduction
observed in B. pumilum may be a reproductive adaptation to life in a fire-prone
habitat. In addition, Chamaesaura anguina a viviparous, arboreal grass lizard also
occurs in the fire-frequent fynbos and exhibits an aseasonal female reproductive
cycle with high clutch sizes; highly unusual for the Cordylidae. With the
observation of two species both inhabiting a fire-driven environment and exhibiting
aseasonal reproductive cycles with high fecundity, it was thought that this
unpredictable environment may shape the reproductive strategies of animals
inhabiting it. However, detailed reproductive data for B. pumilum were unavailable.
The first aim was provide baseline reproductive data for B. pumilum and to discuss
the reproductive strategy in relation to a fire-prone environment. To establish the
significance of fire in the reproductive strategy of B. pumilum, reproductive data of
other Bradypodion species, not inhabiting the fire-prone area was required. The
second aim was to provide baseline reproductive data for Bradypodion with
discussion on possible scenarios facilitating the evolution of dwarf chameleon
reproduction. Bradypodion pumilum specimens were collected in monthly samples
from Stellenbosch and Somerset West in the Western Cape, South Africa.
Specimens of other Bradypodion species were obtained from South African
museums. Data were collected for both sexes of Bradypodion, and sperm storage ability was investigated in B. pumilum. Bradypodion females all showed an
aseasonal reproductive cycle with relatively high clutch sizes for their body size
and the possibility of individual females producing multiple clutches per year. Male
Bradypodion have sperm available the entire year round however, there appears
to be an increase in sperm production in autumn and again in spring in B.
pumilum. Elements of this bimodal pattern are seen in other Bradypodion species.
Dwarf chameleons regardless of habitat and associated climatic conditions are
thus able to reproduce through out the year. It has also been demonstrated in B.
pumilum that both sexes are able to store sperm and it is expected that other
Bradypodion species would posses this character. This type of reproductive
strategy is highly unusual for viviparous, temperate-zone lizards. It is likely that the
cooling of the climate due to the development of the Benguela current facilitated
the transition to viviparity in Bradypodion. Bradypodion may be aseasonal
reproducers for a number of reasons. They are of tropical ancestry, they relatively
recently inhabited tropical forests, or fluctuations in climate may have caused this.
Bradypodion most likely have a high reproductive output due to their intense
vulnerability to predation as in other chameleon species. The proposed hypothesis
that the unusual reproductive characteristics of B. pumilum (and possibly the
ancestral Bradypodion) were due to inhabiting a fire-prone environment now
appears an unlikely explanation. However, even if this extraordinary reproduction
was not in direct response to fire, the strategy appears beneficial in this type of
unpredictable environment. / AFRIKAANSE OPSOMMING: Suid-Afrika, Lesotho en Swaziland huisves ‘n endemiese groep van
dwergverkleurmannetjies (Bradypodion). Hulle is klein, lewendbarende,
insekvretende, arboreale akkedisse en word gevind in ‘n verskeidenheid van
plantegroeitipes en klimaatsomstandighede. Vorige studies op Bradypodion
pumilum dui op ‘n verlengde broeiseisoen en hoë fekunditeit, wat ongewoon is vir
‘n lewendbarende akkedis wat in ‘n Mediterreense omgewing voorkom. Daar is
voorheen voorgestel dat die skynbare verlengde voortplanting in B. pumilum ‘n
aanpassing tot oorlewing in hoogs brandvatbare habitat kan wees. Chamaesaura
anguina is ook ‘n lewenbarende, arboreale akkedis wat in fynbos voorkom wat
hoogs vatbaar is vir brande en groot werpsels produseer en ‘n aseisoenale
voortplantingsiklus in wyfies toon; hierdie patroon is ongewoon vir lede van die
Cordylidae. Met die waarneming dat twee species wat in ‘n brandvatbare
omgewing voorkom albei aseisoenale voortplantingsiklusse en hoë fekunditeit
toon, het die gedagte ontstaan dat hierdie onvoorspelbare omgewing die
voortplantingstrategieë van diere wat daarin voorkom, bepaal. Gedetailleerde
voortplantingsdata ontbreek egter vir B. pumilum. Die eerste doelstelling van die
studie was dus om basisinligting te voorsien oor voortplanting by B. pumilum en
om die voortplantingstrategie aan die hand van die brandvatbare omgewing te
bespreek. Om die moontlike rol van brand in die vorming van die
voortplantingstrategie van B. pumilum te ondersoek, is voortplantingsdata vir
ander Bradypodion species wat nie in brandvatbare habitat voorkom nie, nodig.
Die tweede doelstelling was dus om basisinligting oor voortplanting by
Bradypodion in die breë in te samel, gevolg deur bespreking van moontlike
scenarios in die evolusie van voortplanting by dwergverkleurmannetjies. Bradypodion pumilum eksemplare is maandeliks versamel te Stellenbosch en
Somerset-wes in die Weskaap, Suid-Afrika. Eksemplare van ander Bradypodion
species is vanaf Suid-Afrikaanse museums verky. Data is vir beide geslagte van
Bradypodion versamel, en die vermoë tot spermstoring in B. pumilum bepaal.
Bradypodion wyfies het almal ‘n aseisonale voortplantingsiklus getoon met relatief
hoë werpselgroottes vir hul liggaamsgrootte en daar bestaan die moontlikheid dat
individuele wyfies verskeie werpsels per jaar kan lewer. Bradypodion mannetjies
produseer sperms dwarsdeur die hele jaar, maar daar blyk tog ‘n toename in
spermstoring te wees in die herfs en weer in die lente in B. pumilum. Spore van
hierdie bimodale patroon word in ander Bradypodion species gesien.
Dwergverkleurmannetjies is dus instaat om dwardeur die jaar voort te plant,
ongeag die habitat en geassosieerde klimaatsomstandighede. Daar is getoon dat
beide geslagte van B. pumilum sperms kan stoor en daar word verwag dat ander
Bradypodion species ook hierdie vermoë het. Hierdie tipe van
voortplantingstrategie is ongewoon vir lewendbarende akkedisse van die
gematigde sone. Dit is moontlik dat die ontwikkeling van ‘n koue klimaat weens die
onstaan van die Benguela-stroom aanleiding gegee het tot die oorskakeling na
lewendbarendheid in Bradypodion. Bradypodion mag aseisonale voortplanting
toon vir ‘n aantal moontlike redes. Hulle is van tropiese oorsprong, het redelik
onlangs tropiese woude betrek, of fluktuasies in klimaat kon ook die oorsaak
wees. Bradypodion het waarskynlik hoë voortplantingsuitset omdat hulle besonder
kwesbaar is vir predasie, soos dit die geval is by ander verkleurmannetjies. Die
aanvanklike hipotese dat die ongewone voortplantingseienskappe van B. pumilum
(en moontlik die voorvaderlike Bradypodion) ‘n gevolg is van lewe in ‘n hoogs
brandvatbare omgewing, blyk nou ‘n onwaarskynlik te wees. Selfs as hierdie buitengewone voortplantingstrategie nie ‘n direkte gevolg van brandvatbaarheid is
nie, blyk die strategie voordelig te wees vir oorlewing in hierdie onvoorspelbare
omgewing.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21628 |
| Date | 12 1900 |
| Creators | Jackson, Jennifer C. (Jennifer Claire) |
| Contributors | Mouton, P. le F.N., Flemming, A.F., 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 | English |
| Type | Thesis |
| Format | xxix, 148 leaves : ill. |
| Rights | Stellenbosch University |
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