Deciphering the taxonomic status of parasitic sucking lice occurring on the Aethomys and Micaelamys rodent species complex : a comparative phylogenetic and phylogeographic approach

Bothma, J. C. (2019-12)

Thesis (MSc)--Stellenbosch University, 2019.

Thesis

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 It can thus be proposed that the parasite-host species lists are outdated and that a taxonomic revision for parasites occurring on these rodents are needed.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.

AFRIKAANSE OPSOMMING: Die huidige studie ondersoek die filogenetiese en filogeografiese strukture van parasiete en hul gashere in ‘n poging om die meganismes betrokke by parasietevolusie beter te verstaan. Filogenetiese of filogeografiese ooreenkomste tussen 'n parasiet en sy gasheer sal die hipotese ondersteun dat die evolusie van die parasiete nou verband hou met die evolusie van die gasheerspesies. Verskille in die evolusionêre patrone van die parasiete en die gasheer, sal op sy beurt die voorspelling ondersteun dat parasiet evolusie eerder die resultaat is van onder andere 'n komplekse interaksie tussen die lewensgeskiedenis van gashere, die lewensgeskiedenis van parasiete, asook biogeografie. Om meer duidelikheid te verkry oor die faktore wat parasietevolusie beïnvloed, gebruik die huidige studie mitokondriale - en kern DNA data om genetiese ko-evolusie te ondersoek tussen permanente luis taksa wat voorkom op vier knaagdier spesies wat geassosieer word met die Aethomys/Micaelamys spesie kompleks in Suid Afrika. Onlangs gepubliseerde genetiese studies het veranderinge in die taksonomie van die groep voorgestel en gewys dat die subgenera Micaelamys en Aethomys binne Suid-Afrika as afsonderlike genera erken moet word. Die studies het ook bewys dat die kriptiese A. chrysophilus en A. ineptus as twee afsonderlike spesies erken moet word. Die taksonomiese beskrywings van die luise wat met hierdie knaagdiere geassosieer word het nie hierdie veranderinge in gasheer-taksonomie in ag geneem nie, en die parasiet taksonomie was uitsluitlik gebaseer op morfologie. As gevolg hiervan is dit waarskynlik dat die parasiet-gasheer beskrywings verouderd is. Nietemin is daar gerapporteer dat M. namaquensis en A. chrysophilus albei deur dieselfde spesies luise, naamlik Hoplopleura patersoni en Polyplax praomydis geparasiteer word. Vir M. granti en A. ineptus is daar geen inligting oor die luise wat met hulle geassosieer word nie. Die doelwitte van hierdie projek was om i) die luise wat op die Aethomys en Micaelamys species in Suid-Afrika voorkom te identifiseer; ii) filogenetiese ko-divergensie tussen parasiete en gashere te ondersoek vir al die luise wat op die vier gasheer spesies gevind word; iii) om ‘n fynskaalse analise te onderneem om te toets vir filogeografiese kongruensie tussen een wydverspreide gasheerspesie, M. namaquensis, en sy verwante luise. COI mitokondriale DNA haplotipe netwerke en Bayesiaanse en Maksimum waarskynlikheid fylogenetiese ontledings op 24 gasheer- en 74 luismonsters ondersteun vier geneties verskillende Hoplopleura taksa wat elk met een van die knaagdierspesies geassosieer word. Twee geneties verskillende Polyplax taksa is ook op die twee Micaelamys spesies aangetref. Geen Polyplax individue is op enige van die Aethomys spesies gekry nie. Daar was ook aanduidings dat Hoplopleura en Polyplax individue wat verwyder is van M. namaquensis vanaf die noordooste en suidweste van Suid-Afrika beduidend gedifferensieer is. In totaal het hierdie studie agt geneties gedifferensieerde stamme geïdentifiseer wat met die Aethomys/Micaelamys knaagdier kompleks in Suid-Afrika geassosieer word. Voorlopige morfologiese ondersoeke van hierdie agt stamme het ten minste twee morfologies verskillende Hoplopleura taksa en twee morphologies verskillende Polyplax taksa geopenbaar wat op die twee Micaelamys spesies onderskeidelik voorkom. Op grond van morfologiese verskille, 'n mate van kern DNA differensiasie, en meer as 20% mitokondriale DNA-volgorde afstande tussen hierdie stamme kan 'n sterk argument aangevoer word dat hierdie vier stamme ten minste vier verskillende parasiet spesies verteenwoordig, waarvan twee onbeskryf is. Die filogenie van die luis spesies toon sterk ooreenkomste met die filogenie van die gashere en die tydsberekening van skeidings tussen die gasheerstamme het ook beduidende oorvleueling getoon met die van die parasiete. Topologie gebaseerde versoenings ontledings in Jane ondersteun die idee van ko-divergensie tussen die luise en die gashere as die mees parsimoniese oplossing. In hierdie geval ondersteun die studie die hipotese dat die evolusie van permanente gasheer spesifieke parasiete nou verband hou met die evolusie van hul gasheerspesies. Die invloed van gasheer evolusie op parasiet evolusie is ook deels weerspieël in die filogeografiese ontledings van die twee luise wat op M. namaquensis voorkom. Die COI mitokondriale DNA haplotipe netwerke saam met Bayesiaanse en Maksimum waarskynlikheid filogenetiese ontledings ondersteun kriptiese diversiteit binne P. praomydis en H. patersoni wat van M. namaquensis individue regoor Suid-Afrika versamel is. Beide die gasheer en die parasiete toon 'n beduidende differensiasie tussen stamme in die noordoostelike en suidwestelike dele van Suid-Afrika. Analise van molekulêre variansie ondersteun hierdie differensiasie en stel ook lae vlakke van geenvloei tussen die meeste lokaliteite voor. Beduidende bevolkingsdifferensiasie was teenwoordig vir beide M. namaquensis en die twee luis spesies wat permanent op die gasheer voorkom. Op die filogeografiese vlak het ko-divergensie analises egter 'n onvolledige filogeografiese ooreenkoms tussen M. namaquensis en H. patersoni aangedui. Filogeografiese verskille tussen gasheer en parasiet was hoofsaaklik beperk tot die stamme wat in die noordoostelike streke van Suid-Afrika voorkom. Filogenetiese versoening het aangedui dat hierdie verskille waarskynlik die gevolg is van 'n gasheerruiling. Hierdie onvolledige ooreenkomste dui daarop dat alternatiewe faktore soos die lewensgeskiedenis van die gasheer ook 'n rol speel in die verspreiding en daaropvolgende evolusie van parasiete. In hierdie spesifieke geval is geargumenteer dat manlik bevoordeelde beweging oor korter afstande in die gasheer onvolledige filogeografiese ooreenkoms patrone kan veroorsaak deur meer geleenthede vir gasheerruiling toe te laat.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106990
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