Evolution and Morphological Shape Ontogeny of the Brown ticks (Acari: Ixodida: Ixodidae: Rhipicephalus)
| dc.contributor.advisor | Matthee, Conrad A. | en_ZA |
| dc.contributor.author | Bakkes, Deon Kahlil | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. | en_ZA |
| dc.date.accessioned | 2021-02-15T10:48:12Z | |
| dc.date.accessioned | 2021-04-22T10:11:25Z | |
| dc.date.available | 2021-08-15T03:00:12Z | |
| dc.date.issued | 2021-04 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Rhipicephalus constitute a species-diverse genus of mammal ectoparasites mainly distributed in the Afrotropics that are characterised by generally inornate, uniform brown body colour, short hypostome and palps, basis capituli approximately hexagonal, eyes present and male adanal plates present. They transmit microparasites such as Rickettsia spp., Theileria spp. and Babesia spp. to livestock and humans alike, and some inject neurotoxins during feeding that lead to tick paralysis in livestock. This work infers the phylogeny of Rhipicephalus from molecular lines of evidence (12S, 16S, COI and 28S-D2) and uses this as a basis to infer aspects of their evolutionary history, ecology and evolutionary-development based on geographic distribution data and basis capitulum shape data. Analyses included estimation of divergence times, ancestral area optimisations, ancestral host-use optimisations in immatures and adults, as well as estimations of ancestral climate niches. Basis capitulum morphology is quantified to determine evolutionary- developmental modifications, which are linked to similar patterns in overall body size. Major outcomes of studying Rhipicephalus evolution are 1) radiations coincide with mammal evolution and dispersal, 2) host-use at immature stages partially explain extent of geographic ranges as well as basis capitulum morphology for boring into thick host skin, 3) evolutionary host switches were facilitated by off-host periods and nested connections in predator-prey food webs, 4) speciation partially resulted from niche partitioning along temperature variation gradients, which was reinforced by interspecific competition, and 5) evolutionary-developmental modification (basis capitulum and overall body size) resulted from responses to distinct sets of selection pressure in on- and off-host environments taking into account one-, two- and three-host life cycles. The persistent taxonomic problem of R. turanicus between Palearctic and Afrotropical regions was investigated using integrated lines of evidence to test the species boundary in an iterative framework. This revealed two distinct species in these regions, and the Afrotropical species is described under the name R. afranicus. Another aim of this work was to test the hypothesis of phylogenetic recapitulation in post-embryonic stages of Rhipicephalus basis capituli, where early developmental stages resemble ancestral adults. However, findings indicate no signal for phylogenetic recapitulation is present, most likely due to the action of selection that shape basis capituli over evolutionary timescales. Selection supersedes any possible background action of condensing selection through development that would produce phylogenetic recapitulation. As such, this work serves as a first step for investigating phylogenetic recapitulation using shape data, and suggests future investigation should consider embryonic life stages, alternative features under less selection, or wider phylogenetic comparisons. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.embargo.terms | 2021-08-15 | |
| dc.format.extent | viii, 164 pages : illustrations (some color), maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/110259 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Ticks -- Phylogeny | en_ZA |
| dc.subject | Brown ticks -- Parasites -- Identification | en_ZA |
| dc.subject | Brown dog tick | en_ZA |
| dc.subject | Rhipicephalus -- Morphology | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Evolution and Morphological Shape Ontogeny of the Brown ticks (Acari: Ixodida: Ixodidae: Rhipicephalus) | en_ZA |
| dc.type | Thesis | en_ZA |