Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Physiological diversity in insects was investigated in terms of gas exchange patterns and
metabolic rate. Since the majority of hypotheses that propose to explain the occurrence of
Discontinuous Gas Exchange Cycles (DGCs) are adaptive, the possibility of adaptation
was explored in two ways. First, since repeatability is one of the three prerequisites for
natural selection, and rarely tested in insects, the repeatability of gas exchange
characteristics and metabolic rate were tested in a Perisphaeria sp. cockroach. Four major
gas exchange patterns were recognized and these patterns were found to be extremely
variable within this species. However, repeatability was still generally high for the majority
of the gas exchange characteristics and metabolic rate. Moreover, between individual
variability generally accounted for a large proportion of the variance, supporting the
repeatability findings. Therefore, both metabolic rate and gas exchange patterns might
indeed be adaptive traits in this Perisphaeria sp. cockroach. Second, the distribution of the
three gas exchange patterns (DGCs, cyclic and continuous) across the insect phylogeny
was investigated. Data were extracted from the literature and gas exchange patterns for
eight insect orders, representing mainly the endopterygotes, were measured. Using
standard respirometry techniques, data for a total of ten additional orders were added,
which represented both apterygote orders, six exopterygote orders and two endopterygote
orders that were previously uninvestigated. In addition, four of the five adaptive
hypotheses were tested by investigating the occurrence of DGCs in winged or wingless
insects, subterranean and non-subterranean insects, and insects from mesic and xeric
environments. Results indicate that DGC has evolved at least five times in the insects and
that the cyclic gas exchange pattern is likely to be basal. No support was found for the
chthonic, hybrid and oxidative damage hypotheses, while DGCs were associated with xeric
environments. This analysis provides some support for the hygric hypothesis. In addition the prediction of the fractal network model for metabolic scaling which states that both
intra- and interspecific scaling coefficients should be identical and equal to 0.75, was
tested. Three species of polymorphic worker ants were used to determine the intraspecific
scaling coefficient. Data from the literature were added to provide metabolic rate
information on 42 species of the Formicidae. The interspecific scaling coefficient was
determined in several ways: the traditional method (Ordinary Least Squares regression
models), with the two respirometry techniques analyzed separately or in combination (e.g.
open and closed system), and using phylogenetic independent contrasts with the same sets
of data. Intraspecific coefficients were significantly different from 0.75. The slope of the
interspecific regression obtained using Ordinary Least Squares regression models was not
significantly different from 0.75. However, when phylogenetic relatedness was accounted
for the slope differed significantly from 0.75. Therefore, the fractal network model was not
supported by these findings, since slope values are not equal and also not statistically
equivalent to 0.75. Overall, variability of both metabolic rate and gas exchange patterns in
insects is higher than generally suggested by the literature. These findings provide much
scope for future work. / AFRIKAANSE OPSOMMING: Hier word die fisiologiese diversiteit van insekte ondersoek in terme van hul gaswisselings
patrone asook hul metaboliese tempo. Die oorgrote meerderheid van die hipoteses wat
voorgestel is om die onstaan en bestaan van Diskontinue Gaswisseling in insekte te
verklaar, is op ‘n evolusionêre grondslag gebaseer. Vir hierdie rede word die moontlikheid
van Diskontinue Gaswisseling as ‘n aanpassing op twee maniere ondersoek.
Herhaalbaarheid is een van die voorvereistes van aanpassing (in terme van evolusie) en dit
is tot dusver slegs ‘n paar keer in insekte getoets is. Daarom word die herhaalbaarheid van
die gaswisselings komponente, asook die metaboliese tempo hier in ‘n Perisphaeria sp.
kokkerot ondersoek. Vier hoof gaswisselings patrone is geidentifiseer en die bevinding was
dat die patrone geweldig kan varieer binne hierdie spesie. Ten spyte hiervan was die
herhaalbaarheid steeds hoog vir die oorgrote meerderheid van die gaswisselings
komponente asook vir die metaboliese tempo. Verder het die variasie tussen individue tot
‘n groot proporsie van die totale variasie bygedra, wat die betekenisvolheid van die hoë
herhaalbaarheid beklemtoon. Dus, beide metaboliese tempo sowel as gaswisselings
komponente kan moontlik as ‘n aanpassing beskou word in hierdie kokkerot. Tweedens,
die verspreiding van die drie gaswisselings patrone (Diskontinue Gaswisseling, siklies en
kontinu) in die insekte is ondersoek. Gaswisselings patrone vir agt van die dertig insek
ordes is vanuit die literatuur verkry, alhoewel dit meestal verteenwoordigend van die
Endopterygota is. Data vir tien additionele ordes wat nog nooit voorheen ondersoek is nie
is bygevoeg, insluitende beide die ordes van Apterygota en ses ordes van die Exopterygota,
asook twee ordes van die Endopterygota. Verder is vier van die vyf hipoteses met
betrekking tot aanpassing ondersoek deur die teenwoordigheid van Diskontinue
Gaswisseling in gevleuelde en ongevleuelde insekte, ondergrondse en bogrondse insekte,
asook insekte van gematigde en droeë omgewings te ondersoek. Resultate dui aan dat Diskontinue Gaswisseling ten minste vyf keer onafhanklik in insekte onstaan het en dat die
sikliese patroon heel moontlik basaal is. Die resultate bied geen ondersteuning vir die
hipoteses wat gegrond is op gaswisseling in ondergrondse omgewing of oksidasie
beskerming nie. Daar is wel ondersteuning vir die hipotese aangaande die rol van water
verlies in die onstaan en onderhoud van Diskontinue Gaswisseling. Additioneel is daar
ondersoek ingestel na die verwagting wat deur die fraktale netwerk model vir metaboliese
glyskale gestel word, wat lui dat beide die binne- sowel as tussen-spesies koëffisiënte
identies aan mekaar en gelyk aan 0.75 sal wees. Drie polimorfiese mier spesies is gebruik
om die binne-spesies koëffisiënt te bepaal. Data vanuit die literatuur is hier bygevoeg en
sodoende was informasie vir 42 mier spesies van die Formicidae beskikbaar. Verskillende
metodes is gebruik om die tussen-spesies koëffisiënt te bepaal: die tradisionele metode (sg.
“OLS”-regressie), met die twee tegnieke om metaboliese tempo te bepaal (bv. oop en
geslote sisteem metodes) apart asook saam, en deur gebruik te maak van filogeneties
onafhanklike vergelykings vir dieselfde datastelle. Die binne-spesies koëffisiënte was
almal betekenisvol verskillend van 0.75. Die tussen-spesies regressie waar gebruik gemaak
is van ‘n “OLS”-regressie model was nie betekensivol verskillend van 0.75 nie. Met
filogenetiese verwantskappe egter in ag geneem, het die koëffisiënt wel betekenisvol
verskil van 0.75. Dus word die fraktale netwerk model nie ondersteun deur hierdie studie
nie, aangesien die koëffisiënte nie indenties aan mekaar is nie, en ook statisties verskil van
0.75. In die algemeen is die variasie in metaboliese tempo sowel as gaswisselings patrone
aansienlik hoër as wat afgelei kan word uit die literatuur. Hierdie bevindinge stel ‘n basis
vir heelwat verdere werk in die toekoms.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20935 |
| Date | 04 1900 |
| Creators | Marais, Elrike |
| Contributors | Chown, S.L., Stellenbosch University. Faculty of Sciene. 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 | ix, 184 leaves : ill. |
| Rights | Stellenbosch University |
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