Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Geographic variation in the presence/absence of generation glands in females of the
cordylus-niger-oelofseni complex was described and correlated with climatic variables.
Preserved and live specimens from 96 localities in the area south of 32°30' S and west of
19°45' E in the Western Cape, South Africa, were examined for the presence or absence of
generation glands. Females from western coastal localities and from the Cape Fold
Mountains generally lack generation glands, while females from inland lowland localities
generally possess glands. A GIS analysis was performed to determine mean annual
minimum temperature, mean annual maximum temperature, potential evaporation, mean
annual precipitation, mean annual fog and mean annual cloud cover measured at 14:00 for
each locality. Discriminant function and canonical analyses showed a highly significant
correlation between the presence and absence of generation glands and five of the six
climatic variables. It is suggested that the high incidence of fog and lower temperatures
experienced along the west coast as a result of the cold Benguela Current, and the high
incidence of orographic fog and cloud cover in the Cape Fold Mountains may affect energy
allocation in females. In order to maintain their reproductive output, females may be
forced to invest less energy in secondary sexual characters such as generation glands.
Interspecific variation in the location, occurrence, number, and age of gland
differentiation was investigated for cordylid lizards. For several species, data were
obtained from the literature and for others data were obtained from material housed in the
Ellerman Collection of the University of Stellenbosch. Cordylus cordylus and C.
cataphractus were used for an evaluation of inter- and intrapopulation variation. Data for
C. cordylus were obtained from five populations on the coastal lowlands of the Western
Cape, while data on C. cataphractus come from the literature. The sex, snout-vent length, and number of generation glands were recorded for a representative sample of lizards at
each locality. While in all species generation glands were located in the femoral region,
Cordylus giganteus and C. microlepidotus had additional generation glands elsewhere on
the body. It is suggested that additional generation glands in these species may be related
to an increased need for chemical communication in a low-visibility environment in the
case of C. giganteus, and in low population densities in the case of C. microlepidotus.
Generation glands are present in all cordylid males, but females of some species may lack
these glands. All cordylids display sexual dimorphism with regards to the presence and
number of generation glands, with males having significantly more glands than females,
indicating that these glands may play a more important role in males than in females. Low
sexual dimorphism in at least two species suggests that generation glands may be equally
important in both sexes of these species. In females, the presence of generation glands is
closely regulated by climate. There is no indication of differences in generation gland
profile between ground-dwelling and rock-dwelling species, except that in at least three
ground-dwelling species, generation glands are already present at birth. In other species
these glands differentiate only later in life. In the males of most species, generation glands
start to differentiate prior to or at sexual maturity with a drastic increase in number when
asymptotic body size is reached. The considerable inter- and intrapopulation variation in
gland number in females, but not in males, underscores the hypothesis that the presence of
generation glands in females is energy-linked and closely regulated by climate. An
opposite geographic pattern of generation gland number in C. cataphractus, suggests that
other factors than climate must be responsible for a difference in gland number and a
difference in population density is suggested as explanation.
To test for differences in aggression levels, females with and those without generation
glands were staged in two experiments. In one experiment, females from different localities were staged against each other, while females from the same locality were paired
in another experiment. No significant difference in aggression levels between females
with and those without generation glands were observed in both experiments. It is
suggested that generation glands do not exclusively function in territorial marking, but
rather as a scent enhancer for femoral gland secretions.
Inorder to elucidate the functional significance of generation glands, male response to
female gland stimuli was investigated for 12 male C. cordylus. Males were presented with
different female gland secretions (femoral, generation, and femoral and generation gland
secretion combined) and water was used as a control. Total number of tongue-flicks and
number of tongue-flicks directed at the secretion were counted. No significant difference
was observed in the number of tongue-flicks between the different treatment groups.
Males did, however, display leg-waving and head-rubbing behaviour. At present, the
behaviour displayed by male C. cordylus in the presence of female gland stimuli, is
unclear. The general absence of tongue-flicking of sandpaper labelled by female gland
stimuli may be because of a flaw in the experimental design or because the experiment was
conducted outside the breeding season. The display ofleg-waving and head-rubbing
behaviour, however, suggests that cordylids do not exclusively rely on tongue-flicking for
detection of conspecifics. The real function of generation glands thus still remains
unresolved and further studies are needed to clarify this. / AFRIKAANSE OPSOMMING: Geografiese variasie in die aan-/afwesigheid van generasiekliere in wyfies van die
cordylus-niger-oelofseni kompleks is beskryf en met klimaatsveranderlikes gekorreleer.
Gepreserveerde en lewende materiaal, afkomstig van 96 lokaliteite in die area suid van
32°30' S en wes van 19°45'0 in die Wes-Kaap, Suid-Afrika, is vir die aan- ofafwesigheid
van generasiekliere ondersoek. Generasiekliere is oor die algemeen afwesig in wyfies van
westelike kuslokaliteite en die Kaapse Plooiberge, terwyl dit aanwesig is in wyfies van die
binnelandse laagland lokaliteite. 'n GIS-analise is gedoen om die gemiddelde jaarlikse
minimum temperatuur, gemiddelde jaarlikse maksimum temperatuur, potensiële
verdamping, gemiddelde jaarlikse neerslag, gemiddelde jaarlikse mis en gemiddelde
jaarlikse wolkbedekking, gemeet teen 14:00, vir elke lokaliteit te bepaal. Diskriminantefunksie
en kanonieke analises toon 'n hoogs beduidende korrelasie tussen die aan- en
afwesigheid van kliere en vyf van die ses klimaatsveranderlikes. Daar word voorgestel dat
die hoë voorkoms van mis en lae temperature wat langs die weskus ervaar word as gevolg
van die koue Benguela Seestroom, en die hoë voorkoms van orografiese mis en
wolkbedekking in die Kaapse Plooiberge, die energie-toekenning in wyfies beïnvloed. Om
hulle voortplantingsuitset te handhaaf, word wyfies moontlik gedwing om minder energie
in sekondêre geslagskenmerke, soos generasiekliere, te belê.
Interspesifieke variasie in die posisie, voorkoms, aantal en tyd van klierontwikkeling is
vir verskeie gordelakkedisspesies ondersoek. Data vir verskeie spesies is vanuit die
literatuur verkry, terwyl data vir ander spesies vanafmaterial in die Ellerman-versameling
van die Universiteit van Stellenbosch verkry is. Cordylus cordylus en C. cataphractus is
vir 'n evaluering van inter- en intrapopulasie variasie gebruik. Data vir C. cordylus is
vanafvyfpopulasie wat op die kuslaaglande van die Wes-Kaap voorkom, ingesamel, terwyl data oor C. cataphractus vanuit die literatuur verkry is. Geslag, snoet-kloaak-lengte
en die aantal generasiekliere is aangeteken vir 'n verteenwoordigende aantal individue van
elke populasie. Terwyl generasiekliere in die femorale wyk van alle spesies aangetref
word, het Cordylus giganteus en C. microlepidotus ook addisionele generasiekliere in
ander dele van die liggaam. Daar is tot die gevolgtrekking gekom dat addisionele
generasiekliere in hierdie spesies moontlik verwant is aan 'n groter behoefte aan chemiese
kommunikasie in 'n lae sigbaarheidsomgewing in die geval van C. giganteus, en in 'n lae
populasiedigtheid in die geval van C. microlepidotus. Generasiekliere word in alle
gordelakkedis mannetjies aangetref, maar kan afwesig wees in wyfies van sommige
spesies. Alle gordelakkedisse toon geslagsdimorfisme met betrekking tot die aanwesigheid
en aantal generasiekliere, en mannetjies het beduidend meer kliere as wyfies, wat daarop
dui dat hierdie kliere moontlik 'n meer belangrike rol by mannetjies as by wyfies speel.
Lae geslagsdimorfisme inten minste twee spesies stel voor dat generasiekliere moontlik
ewe belangrik in beide geslagte van hierdie spesies kan wees. In wyfies word die
aanwesigheid van generasiekliere sterk deur klimaat gereguleer. Daar is geen aanduiding
van verskille in generasieklierprofiel tussen grondbewonende en rotsbewonende spesies
nie, behalwe dat generasiekliere reeds by geboorte teenwoordig is in ten minste drie
grondbewonende spesies. In ander spesies ontwikkel hierdie kliere eers later. In
mannetjies van die meeste spesies, begin generasiekliere voor oftydens geslagsrypheid
ontwikkel, met 'n drastiese toename in aantal kliere wanneer asimptotiese liggaamsgrootte
bereik word. Die aansienlike inter- en intrapopulasie variasie in aantal kliere in wyfies,
maar nie in mannetjies nie, ondersteun die hipotese dat die teenwoordigheid van
generasiekliere in wyfies aan energie gekoppel is en deur klimaat gereguleer word. 'n
Teenoorgestelde geografiese patroon in die aantal generasiekliere in C. cataphractus, stel voor dat ander faktore as klimaat vir die verskil in aantal kliere verantwoordelik is en 'n
verskil in populasiedigtheid word as verklaring voorgestel.
Om vir verskille in aggressievlakke te toets, is wyfies met en wyfies sonder
generasiekliere is teenoor mekaar getoets in twee eksperimente. In een eksperiment is
wyfies van verskillende lokaliteite teenoor mekaar getoets, en in 'n ander eksperiment is
wyfies van dieselfde lokaliteit teenoor mekaar getoets. Inbeide eksperimente is geen
beduidende verskille is in die aggressievlakke van wyfies nie waargeneem nie. Daar word
voorgestel dat generasiekliere nie uitsluitlik in gebiedsafbakening funksioneer nie, maar
dat dit eerder as reukversterker vir die femorale kliere dien.
Om die funksie van generasiekliere vas te stel, is die reaksie van 12 mannetjie C.
cordylus op klierstimuli van wyfies getoets. Verskillende kliersekresies (femoraal,
generasie, en femoraal en generasie gekombineerd) van wyfies is mannetjies voorgelê, en
water is as 'n kontrole gebruik. Totale aantal tongskiete en aantal tongskiete wat na die
sekresie gerig is, is getel. Geen beduidende verskil in die aantal tongskiete is tussen die
verskillende groepe waargeneem nie. Mannetjies het egter beenwaai- en kopvryfgedrag
getoon. Die rede vir die gedrag wat deur C. cordylus mannetjies in die teenwoordigheid
van klierstimuli van wyfies vertoon word, is egter tans onduidelik. Die algemene
afwesigheid van tongskiete na skuurpapier wat met klierstimuli van wyfies gemerk is, mag
moontlik wees as gevolg van 'n fout in die eksperimentele ontwerp of omdat die
eksperiment buite die paarseisoen uitgevoer is. Die vertoning van beenwaai- en
kopvryfgedrag stel egter voor dat gordelakkedisse nie uitsluitlik op tongskiete staatmaak
om lede van dieselfde spesie waar te neem nie. Die ware funksie van generasiekliere is
dus steeds onopgelos en verdere studies word benodig om dit duidelikheid hieroor te kry.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49975 |
| Date | 03 1900 |
| Creators | Du Toit, Dahne A. (Dahne Anne) |
| Contributors | Mouton, P. N. L., 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 | 108 p. : ill. |
| Rights | Stellenbosch University |
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