Browsing by Author "Bothma, J. C."
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- ItemDeciphering the taxonomic status of parasitic sucking lice occurring on the Aethomys and Micaelamys rodent species complex : a comparative phylogenetic and phylogeographic approach(Stellenbosch : Stellenbosch University, 2019-12) Bothma, J. C.; Sonja, Matthee; Conrad, Matthee; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.ENGLISH ABSTRACT: The present study investigated the phylogenetic and phylogeographic structures of parasites and their hosts in an attempt to better understand the mechanisms involved in parasite evolution. Phylogenetic or phylogeographic co-divergence between a parasite and its host would support a hypothesis that the evolution of parasites are closely linked to the evolution of host species. The lack of co-divergences would support the prediction that parasite evolution is the result of, amongst others, a complex interaction between host life history, parasite life history and biogeography. To provide more clarity on the factors influencing parasite evolution, the present study used mitochondrial - and nuclear DNA sequence data to investigate genetic co-divergences between obligate permanent lice species occurring on four rodent taxa associated with the Aethomys/Micaelamys species complex. Recent genetic investigations provided new taxonomic insights into the phylogeny of the host species and supported that within South Africa the subgenera Micaelamys and Aethomys should be recognized as distinct genera. It also provided evidence that the cryptic A. chrysophilus and A. ineptus should be recognized as two different species. The taxonomic descriptions of the lice that are associated with these rodents did not take into account the recent vacillations in host taxonomy and parasite species descriptions were exclusively based on morphology. It can thus be proposed that the parasite-host species lists are outdated and that a taxonomic revision for parasites occurring on these rodents are needed. Nonetheless, it has been reported that M. namaquensis and A. chrysophilus are both parasitized by the same species of lice, namely Hoplopleura patersoni and Polyplax praomydis. For M. granti and the newly erected species, A.ineptus, there are no data on the lice species that are associated with them. The aims of this projectwere to i) identify the sucking lice associated with Aethomys and Micaelamys species occurring in South Africa, ii) investigate phylogenetic co-diverge between parasites and hosts for all the lice species sampled on the four host lineages, iii) conduct a fine scale co-divergence analyses by testing for phylogeographic congruence between one widely distributed host species, M. namaquensis, and its associated lice species. COI mitochondrial DNA haplotype networks and Bayesian and Maximum likelihood phylogenetic analyses drawn from 24 host and 74 louse specimens supported four genetically distinct Hoplopleura taxa each associated with a different rodent species. Two genetically distinct Polyplax taxa were also detected on the two Micaelamys species. No Polyplax individuals were sampled from the Aethomys individuals included herein. Within the widely distributed M. namaquensis, there was also indications that Hoplopleura - and Polyplax lineages trapped in the north east and south west of South Africa are significantly differentiated from each other. In total, this study identified eight genetically distinct louse lineages associated with the Aethomys/Micaelamys rodent complex in South Africa. Superficial morphological investigations on these eight lineages revealed at least two morphologically distinct Hoplopleura - and two morphologically distinct Polyplax taxa occurring on the two Micaelamys species respectively. Based on morphological differences, some nuclear DNA differentiation, and more than 20% mitochondrial DNA sequence distances between these lineages, a strong argument can be made that these four lineages represent at least four distinct parasite species, two of them new to science. The phylogeny of the lice species showed marked congruences with the phylogeny of the rodent hosts and divergence dating also showed a fair amount of overlap in the timing of the divergences between the host lineages and those of the parasites. Topology based reconciliation analyses in Jane significantly supported the notion of co-divergence between parasite and host lineages as the most parsimonious solution. In this instance the latter provides support for the hypothesis that the evolution of permanent host specific parasites are closely linked to the evolution of their host species. The influence of host evolution on parasite evolution is also partly reflected in the finer scale phylogeographic analyses of the two species of lice occurring on M. namaquensis. The COI mitochondrial DNA haplotype networks along with Bayesian and Maximum likelihood phylogenetic analyses supported cryptic diversity within P. praomydis and H. patersoni collected from M. namaquensis individuals throughout South Africa. Both the host and the parasites show significant differentiation between lineages in the north-eastern and south-western parts of South Africa. Analyses of molecular variance supported this differentiation and also suggested low levels of gene flow among most sampling localities. Significant population differentiation was present for both M. namaquensis and the two lice species occurring permanently on the host. At the phylogeographic level, however, co-divergence analyses indicated limited phylogeographic congruence between M. namaquensis and H. patersoni throughout the sampled range. Incongruences were mainly confined to the lineages occurring in the north-eastern regions of South Africa. Phylogenetic reconciliation indicated that this incongruence is most likely as a result of a host switch. This partial congruence suggests that alternative factors such as host life history also play a role in the dispersal and subsequent evolution of parasites. In this specific instance it was argued that male bias dispersal over shorter distances in the host can cause incongruent patterns by allowing more opportunities for host switching.