The evolution and diversity of parasites of New Zealand lizards

Co-evolution;New Zealand;Spauligodon;Skrjabinodon;gecko;skink;Pharyngodonidae;nematode;Oxyuroidea

Mockett, Sarah Theresa ; Poulin, Robert

University of Otago

关键词: Co-evolution;    New Zealand;    Spauligodon;    Skrjabinodon;    gecko;    skink;    Pharyngodonidae;    nematode;    Oxyuroidea;   

Others  :  https://ourarchive.otago.ac.nz/bitstream/10523/5962/1/MockettSarahT2015MSc.pdf

美国|英语

来源: Otago University Research Archive

【 摘 要 】

Co-phylogenetic studies have been an indispensable tool to unravel the processes and patterns of evolution that occur between parasites and their hosts. Ecto-parasites, so far, have been the main subjects of these studies. However, in order to develop more general rules of evolution, we must study a broader range of parasitic associations. The present study focused on parasitic nematodes, a group that has received relatively little attention from a co-phylogenetic perspective. The aim of the study was to investigate the evolutionary history between New Zealand lizards and their nematode parasites in order to test the following hypothesis: host-nematode associations, in which the parasites have limited dispersal, will follow a mostly co-evolutionary pattern. This research also offered the opportunity to advance our knowledge of NZ reptile parasites by assessing the genetic diversity and phylogenetic relationships of parasitic nematodes, and by conducting a survey of mites parasitic on lizards. Nematodes for this study were collected via searching faecal pellets released by wild lizards and recovering any expelled nematodes. The phylogenetic relationships between the nematodes were explored using three genetic markers: two nuclear (18S rRNA, 28S rRNA) and one mitochondrial (cytochrome oxidase subunit I: COI). Two algorithms, MrBayes and Maximum Likelihood, were used to build gene trees, and between-clade genetic distances were calculated for all markers. Finally, to explore the evolutionary history between these hosts and their parasitic nematodes, the co-evolutionary analysis program PACo was used. The study produced several important findings. First, nematodes from NZ skinks were found to be of the genus Spauligodon rather than Skrjabinodon to which they had previously been assigned. The results also showed that both skink and gecko nematodes contain more diversity than has been previously detected by morphological examinations. This study provides evidence for several provisionally cryptic species. In relation to the main aim, the analysis provides evidence that both co-evolutionary processes (co-speciation) and host switching events have been important in the evolution of NZ lizard nematodes. The study indicates that Farhenholz’s rule does not apply to NZ lizard-nematode associations. However, further sampling is required before we have sufficient evidence to support or reject the main hypothesis. Finally, a survey of parasitic mites of NZ lizards, another parasitic group that has received little attention, was conducted, and complemented by a thorough literature review of existing host and location records. Mites were obtained from lizard hosts already being handled for the collection of parasitic nematodes. The survey produced both new host and locality records, and highlighted the need for future studies focusing on these small native parasites. Overall, the results of this thesis have important implications for biodiversity conservation and for taxonomy of these little-studied parasite groups.