Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Cuticular hydrocarbon (CHC) profiles of insects play roles in behavioural interactions
within and between species, encompassing species-, colony- and mate-recognition.
CHCs are largely genetically determined and are thus unique to each species, making
them useful in chemotaxonomy. However, species exhibit intra-species variation in
their CHC profile which can be the result of both intra-species genetic variation as
well as environmental influences such as habitat effects, colony effects, diet, host
switching, as well as adsorption of CHCs from other insects. Studies have found that
the CHC profiles of a specific insect species will often exhibit variations between
regions as well as the species of host the insect is associated with. Therefore, an ideal
system to investigate the effects of genetic population structure and environment on
the CHC profiles of insects is within the fig – fig wasp mutualism. Fig species occur
in a wide variety of habitats and host a diverse complement of fig wasp species. We
were therefore offered the opportunity to investigate a wide range of potential
influences on fig wasp CHC profiles ranging from environmental to genetic effects.
Firstly, through GC-MS we found that the CHC profiles of the fig wasps investigated
are both species-specific and species-group-specific, with the species Elisabethiella
glumosae, Elisabethiella stuckenbergi and Ceratosolen capensis, and two Otitesella
species-groups (the Uluzi and Sesqui species-groups) separating out significantly.
Consensus phylogenies (based on COI, Cytb and EF-1α) showed that within the
galling fig wasp genus Otitesella there were multiple genetic lineages within a
species-group which corresponds to species-level genetic variation, and that each
genetic lineage was confined to a single host fig species. The CHC profiles reflected
the genetic relationships between the two species-groups, and the CHC profiles within
a species group could be differentiated by genetic lineage/host species. This indicated
that although genetic lineage was mostly responsible for the observed variation in
CHC profiles, factors associated with different host species also had an effect. Strong
regional variation overriding both the influence of genetic lineage and factors
associated with host species were observed in the CHC profiles of the fig wasps
within a species-group. This regional variation in CHC profiles was also observed
within two pollinating fig wasp species, Elisabethiella stuckenbergi and Ceratosolen capensis, which was not supported by population genetic data (COI and Cytb). In fact,
very little genetic population structure was found within the pollinating species, even though the pollinators were collected across South Africa. The lack of genetic
structure in pollinating fig wasps can be the result of high gene flow caused by the
large dispersal capability of pollinating fig wasps. Our results indicated that fig wasp
CHC profiles have the potential to be used in chemotaxonomy and are possibly used
as species and mate-recognition cues by the fig wasps. Furthermore, we found both a
regional and associated host species effect on the CHC profile. We suggest that the
observed regional effect in this study could be attributed to habitat differences and
differences in fig wasp community between regions. Moreover, the effect host species
had on the CHC profiles may be as a result of dietary differences between galls in
different host species. A possible consequence of the observed regional/host speciesassociated
effect on fig wasp CHC profiles is that it could lead to pre-mating isolation
within fig wasp species, which could ultimately result in speciation. In addition, our
results indicated that the interpretation of the variation in the fig wasp CHC profile
was dependent on the scale of the analysis: on a broad, inter-species-level scale, fig
wasp CHC profiles were species-specific; on a finer intra-species scale, variation in
CHC profiles occurred between fig wasps collected from different regions; and on a
within-region scale, variation in CHC profiles within species-groups occurred
between genetic lineages/host species. Future studies should look at the application of
CHCs in chemotaxonomic studies on the fig wasp phylogeny, as well as the effect of
fig wasp community composition on fig wasp CHCs. / AFRIKAANSE OPSOMMING: Kutikulêre koolwaterstof (KK) profiele van insekte speel rolle in die
gedragsinteraksies binne sowel as tussen spesies, en behels die herkenning van spesieof
kolonielidmaatskap asook potensiële maats. Kutikulêre koolwaterstowwe word
meestal deur gene bepaal en is dus uniek vir elke spesie, wat dit handig maak vir
chemotaksonomie. Spesies vertoon egter soms intraspesie variasie in hul KK profiele
wat die gevolg kan wees van beide intraspesie genetiese variasie sowel as
omgewingsinvloede soos habitat effekte, kolonie effekte, dieet, tussen-gasheer
skuiwings, asook die adsorpsie van ander insekte se kutikulêre koolwaterstowwe.
Studies het gevind dat die kutikulêre koolwaterstof profiele van ʼn spesifieke insek
spesie op ʼn gereelde basis verskille vertoon tussen streke asook tussen die
verskillende gasheer spesies waarmee die insek geassosieer is. Om hierdie redes is die
vy – vy-wesp mutualisme ʼn ideale sisteem om die uitwerking van genetiese populasie
struktuur en omgewing op die KK profiele van insekte te ondersoek. Vy spesies kom
in ʼn wye verskeidenheid van habitatte voor en ondersteun ʼn diverse groep vy-wesp
spesies. Dit het ons die geleentheid gebied om ʼn wye reeks moontlike invloede van
vy-wesp KK profiele te ondersoek, van omgewings- tot genetiese invloede. Eerstens,
deur die gebruik van GC-MS het ons gevind dat die KK profiele van die vy-wespe
wat ondersoek was beide spesie-spesifiek en spesie-groep-spesifiek is, met die spesies
Elisabethiella glumosae, Elisabethiella stuckenbergi en Ceratosolen capensis, asook
twee Otitesella spesie-groepe (die Uluzi en Sesqui spesie-groepe) wat betekenisvol
onderskei kon word. Konsensus filogenieë (gegrond op COI, Cytb en EF1-1α) het
getoon dat daar in die gal-induserende vy-wesp genus Otitesella veelvuldige genetiese
lyne binne die spesie-groepe voorgekom het ooreenstemmend met tussen-spesie
genetiese variasie, en dat elke genetiese lyn beperk was tot ʼn enkele gasheer vy
spesie. Die KK profiele het die genetiese verhoudings tussen die twee spesie-groepe
weerspieël, en die KK profiele binne ʼn spesie-groep kon onderskei word op grond van
hul genetiese lyn/gasheer spesie. Hierdie het getoon dat, alhoewel genetiese lyn
meestal verantwoordelik was vir die waargeneemde variasie in KK profiele, faktore
wat met verskille in gasheer spesies gepaard gaan ook ʼn effek gehad het. Sterk
streeks-verbonde variasie wat beide die invloed van genetiese lyn, én faktore wat met
verskille in gasheer spesie gepaard gaan, oortref het, was waargeneem in die KK
profiele van die vy-wespe binne ʼn spesie-groep. Hierdie streeks-verbonde variasie in KK profiele was ook waargeneem in twee bestuiwende vy-wespe, Elisabethiella
stuckenbergi en Ceratosolen capensis, ʼn resultaat wat nie ondersteun was deur die
genetiese bevolkingsdata nie (COI en Cytb). In werklikheid was baie min genetiese
bevolkings-struktuur opgespoor binne die bestuiwer spesies, selfs as was die
bestuiwer spesies regoor Suid-Afrika ingesamel. Die tekort aan genetiese struktuur in
die vy-wesp bestuiwers kan die gevolg wees van hoë geenvloei wat veroorsaak word
deur die hoë verspreidingskapasiteit van bestuiwende vy-wespe. Die resultate toon
aan dat vy-wesp KK profiele die potensiaal besit om in chemotaksonomie gebruik te
word, en word moontlik deur vy-wespe gebruik as kenmerke vir die herkenning van
spesie en potensiële maats. Verder was daar gevind dat daar beide ʼn streekseffek en ʼn
effek geassosieer met gasheer spesie op KK profiele was. Ons stel voor dat die
waargeneemde streekseffek in hierdie studie toegeskryf kan word aan verskille tussen
habitatte asook streeksverbonde verskille tussen vy-wesp gemeenskappe. Boonop kan
die effek wat gasheer spesie op die KK profiele gehad het ʼn gevolg wees van
dieetverskille tussen die galle in verskillende gasheer spesies. ʼn Moontlike gevolg van
die waargeneemde streeks/gasheer-spesie-geassosieerde effek op vy-wesp KK
profiele is dat dit moontlik kon lei tot voor-paring-isolasie binne vy-wesp spesies, wat
uiteindelik spesiasie kon veroorsaak het. Daarbenewens wys ons resultate dat die
interpretasie van die variasie in die vy-wesp KK profiel was afhanklik van die skaal
van die analise: op ʼn breë interspesie vlak was die vy-wesp KK profiele spesiespesifiek;
op ʼn fyner intra-spesie vlak het variasie in KK profiele voorgekom tussen
vy-wespe wat in verskillende streke ingesamel was; en op streeksvlak het variasie in
die KK profiele binne spesie-groepe voorgekom tussen genetiese lyne/gasheer
spesies. Toekomstige studies behoort te kyk na die toepassing van kutikulêre
koolwaterstowwe in chemotaksonomiese studies van die vy-wesp filogenie, asook die
effek wat vy-wesp gemeenskap samestelling het op vy-wesp kutikulêre
koolwaterstowwe.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20359 |
| Date | 03 1900 |
| Creators | Van der Merwe, Julia Frances |
| Contributors | Wossler, Theresa C., Van Noort, Simon, 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 | 119 p. : ill. |
| Rights | Stellenbosch University |
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