Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006. / The Restionaceae is a dominant family in the Fynbos Biome, an area in which fire plays a role as an important disturbance, yet little is known about their population dynamics. Two species of the Restionaceae (Thamnochortus insignis and T. erectus) are economically important as thatching reed and differ in their life-histories. This study aims to determine the effects of variation in life history (sprouter vs. non-sprouter) on the population structure and dynamics of T. erectus (“wyfies riet”, sprouter) and T. insignis (“mannetjies riet”), a non-sprouting species. A matrix-modelling approach based on field data collected by Ball (1995) is used to determine population growth rates, stable stage distributions and stage sensitivity and elasticity for the two species with no disturbance present. The sprouter (T. erectus) shows a positive population growth rate (λ >1) and greater persistence within all stages. The non-sprouting species (T. insignis) shows a negative population growth rate (λ <1) between disturbances as well as greater seed production, germination and growth between stages. Based on the population dynamics of these two species, further research was done to understand the effect of disturbance (harvesting and fire) on these species. A matrix modelling approach was used to determine which disturbance frequency maximises population output and success. Harvesting as well as fire results in a decline in T. insignis populations. A five year frequency for harvesting results in the greatest output of adult plants with the lowest effect on the population, and a fire frequency of 50 to 65 years is recommended. Testing indicates that the model underestimates the number of adults in the population and thus the model is conservative. T. erectus populations grow despite fire or harvesting; thus any reasonable harvesting (3-5 year frequency) and fire (10+ years between fire) regime would ensure population persistence. As data were limited it was not possible to test the results although T. erectus appears resilient to disturbance and therefore a predetermined regime is not as important as in T. insignis. Recommendations to farmers are made based on these results.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Knowledge of the diversity and evolutionary histories of insects in South Africa’s fynbos biome lags far behind what is known of the plant groups that make up this global biodiversity hotspot. To address this imbalance, I undertook a molecular phylogenetic study of fynbos-endemic Cephalelini leafhoppers that specialise on restios in the family Restionaceae. My phylogenetic results did not recover the South African Cephalelini as monophyletic, nor did I find monophyly of described species, but several monophyletic clades of species were found within Cephalelini. Furthermore, phylogenetic dating suggested that the divergence between South African and Australian Cephalelini post-dates Gondwanan vicariance, implying intercontinental extreme long distance dispersal of these insects ca. 5-11 MYA. Diversification within the Cephalelini is also much more recent than that of the Restionaceae hosts on which they specialise, negating the possibility of coevolution between plants and insects. Rather, analysis of phylogenetic conservatism of host use reveals that Cephalelini evolution has tracked the evolution of their Restionaceae hosts and that closely related insects feed on the same plant host tribes. A finer scale of tracking of host evolution (such as at the clade or genus level) is expected when taking into account how highly specific I find Cephalelini host use to be, but its absence might be explained by the recent divergence of Cephalelini relative to the age of Restionaceae. Analysis of conservatism of host use was also carried out using a phylogeny of the Restionaceae, and revealed that, overall, Cephalelini host use and avoidance have no phylogenetic bias, indicating many empty potential niches for Cephalelini, or alternately that host use is governed by factors which are phylogenetically unconstrained. Lastly, I also analysed the evolution of specialisation of Cephalelini and find no trend towards increased specialisation within the group, which is contrary to what is expected of the evolution of herbivorous insects. Overall, this study presents the first evidence of intercontinental dispersal of insect fauna between South Africa and Australia and as such highlights an unconsidered factor in the accumulation of faunal diversity in the fynbos biome. I find Cephalelini to be highly specialised in their host preference, but this pattern only becomes apparent at the tribal host level in the evolution of Cephalelini. Although Cephalelini are highly specialised, I find no evidence of evolution towards increasing specialisation within the group. / AFRIKAANSE OPSOMMING: Ons kennis van die evolusie van fynbosinsekte is redelik beperk vergeleke met hoe veel ons weet van die plante wat die merkwaardige diversiteit van die fynbos-bioom uitmaak. In `n poging om hierdie wanbalans reg te stel het ek `n molekulêr-evolusionêre studie onderneem van die fynbos-endemiese blaarspringer-groep Cephalelini, wat op Restionaceae-gasheerplante spesialiseer. Ons het drie geen-areas geamplifiseer vir filogeniekonstruksie en dateringsdoeleindes: insek-kern H3, insek- mitokondriaal COI en insek-simbiont Sulcia 16S. Met behulp van filogenetiese analise is bevind dat die Suid-Afrikaanse Cephalelini nie `n monofiletiese groep is nie en dat beskryfde spesies ook nie monofileties is nie, maar verskeie monofiletiese spesie-groepe is wel gevind. `n Oorkruis-gevalideerde dateringsoefening dui aan dat divergensie tussen Suid-Afrikaanse en Australiaanse Cephalelini meer onlangs as die verbrokkeling van Gondwana plaasgevind het, wat impliseer dat daar uitruiling van insekte tussen die kontinente oor die afgelope 5-11 MJ plaasgevind het. Die diversiteit van Cephalelini het ook veel meer onlangs ontstaan as dié van hulle Restionacaea-gashere wat beteken dat ko-evolusie in die eng sin nie moontlik is nie. ‘n Ontleding van die evolusie van gasheer-keuse deur Cephalelini dui wel aan dat Cephalelini-evolusie die patron van hul Restionaceae-gashere volg en dat naverwante Cephalelini dieselfde stam van Restionaceae as gashere verkies. Die bevinding dat die Cephalelini hoogs gespesialiseerd is in hulle gasheer-keuses lei ‘n mens tot die verwagting dat die evolusie van Cephalelini meer getrou die evolusie van hulle gashere sal volg as wat wel die geval is (dalk op die vlak van groep of genus), maar die relatiewe jeugdigheid van die Cephalelini vergeleke met die ouderdom van die Restionaceae is moontlik die rede hiervoor. Analise van gasheer-keuse is ook uitgevoer op `n filogenie van die Restionaceae wat aantoon dat daar nie ‘n beperking van verwantskappe is tussen gashere wat verkies of verwerp word nie, wat daarop dui dat daar `n menigte nisse is wat oënskynlik onbenut is, of dat Cephalelini gasheer-keuse bepaal word deur `n Restionaceae-eienskappe wat nie filogeneties beperk is nie. Laastens het ek die evolusie van spesialisering deur Cephalelini ontleed, maar geen neiging tot toenemende spesialisering binne die groep gevind nie, wat onverwags is in die lig van vorige studies. As `n geheel bied hierdie studie die eerste bewys van die uitruiling van insek-fauna tussen die Suid-Afrikaanse fynbos-bioom en ander kontinente, wat `n onopgetekende invloed op die diversiteit van diere in die fynbos is. Cephalelini is `n hoogs gespesialiseerde groep insekte, maar uit `n filogenetiese perspektief word dit eers waargeneem op die vlak van gasheerstam. Ten spyte van hulle hoë vlak van spesialisering het ek geen bewys gevind van `n toename daarin binne die evolusie van die groep nie.

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.