Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Research into the patterns and drivers of insect diversity in the Cape Floristic Region (CFR)
lags far behind that of plants. Here I sample insect herbivore communities on a dominant
plant family (Restionaceae), and use a spatially nested sampling design and network analysis
to evaluate the association between plant and insect diversity in the CFR. I find that plant
species richness predicts insect richness better than environmental factors. Turnover in insect
communities is strongly associated with turnover in plant (both species and phylogenetic)
communities at both local and regional sampling scales, suggesting insect host specificity.
Plant communities unsurprisingly show significant turnover at small spatial scales (i.e.
communities situated 0.1-3 km apart show significant turnover and may be tied to ecological
niches). Insects show a similar pattern, but the decrease in community overlap is more
gradual, suggesting many insects can utilise multiple (possibly closely related) hosts while
plants are tied to particular niches. The emergent structure of multiple interaction networks is
spatially and temporally invariant, despite high compositional change. However, the internal
structure of the networks shows variation (i.e. interactions show spatial and temporal
turnover). Seasonal interaction turnover is driven by a turnover in herbivores and by
herbivore host switching. Spatially the turnover in interactions is driven by simultaneous
turnover in both plants and insects, either suggesting that insects are host specific, or that
both groups exhibit parallel responses to environmental gradients. Spatial interaction turnover
is also driven by a turnover in plants, showing that many insects can utilise multiple (possibly
closely related) hosts and have wider distribution ranges than their host plants. Results point
toward insect host specificity, but probably not at the species level, as the primary mechanism
structuring insect communities associated with the Restionaceae in the CFR. / AFRIKAANSE OPSOMMING: Navorsing wat verband hou met die patrone en meganismes wat insekdiversiteit in the
Kaapse Blommeryk (KBR) hou nie pas met dié van plante nie. In hierdie studie neem ek
insekmonsters binne een van die dominante plantfamilies (Restionaceae), en gebruik ‘n
ruimtelik geneste ontwerp en netwerkanalise om die verbintenis tussen plant- en
insekdiversiteit te evalueer. Ek vind plantrykheid voorspel insekrykheid beter as enige
omgewingsfaktore. ‘n Omset in in insekgemeenskappe is sterk verbind aan ‘n omset in
plantgemeenskappe (beide spesie en filogenetiese) by beide plaaslik en vir die hele streek.
Hierdie dui op insekgasheerspesifisiteit. Plantgemeenskappe wys omset teen kort ruimtelike
skale (0.1-3 km). Insekte wys ‘n soortgelyke patron, maar die afname in oorvleueling tussen
gemeenskappe is meer geredelik. Dit dui dat insek meer as een gasheer kan gebruik, terwyl
plante streng tot sekere nisse verbind is. Die ontluikende struktuur van menigde
interaksienetwerke wys geen ruimtelike of tydelike variasie nie, ten spyte van hoë
gemeenskapsomset. Nietewel, die interne struktuur van die netwerke wys veranderinge
(interaksies in netwerke wys omset). Seisonale interaksie-omset kan toegeskryf word aan ‘n
omset van herbivore en insekgasheerverandering. Ruimtelike interaksie-omset word
toegeskryf aan gelyktydige insek- en plantomset, wat óf deur insekgasheerspesifisiteit
veroorsaak word óf deur parallele reaksies tot omgewingsveranderinge. Ruimtelike
interaksie-omset word ook deur plantomset beïnvloed, wat aandui sommige insekte kan meer
as een gasheer benut en insekte het weier verspreidings as hul gasheer. Resultate dui daarop
dat insekgasheerspesifisiteit, maar waarskynlik nie op die spesievlak nie, moontlik die
primêre meganisme is wat insekgemeenskappe verbind aan die Restionaceae in die KBR
struktureer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96067 |
| Date | 12 1900 |
| Creators | Kemp, Jurene Ellen |
| Contributors | Ellis, Allan George, 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 | x, 91 p. : ill. |
| Rights | Stellenbosch University |
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