Parasites of sleepy lizards (Tiliqua rugosa) sampled across an ecological gradient at Bundey Bore Station, South Australia

Author: Gerrut Norval

Norval, Gerrut, 2022 Parasites of sleepy lizards (Tiliqua rugosa) sampled across an ecological gradient at Bundey Bore Station, South Australia, Flinders University, College of Science and Engineering

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Parasites make up a large part of the world’s biodiversity and are important components of ecosystems because they influence the fitness of their hosts, and therefore intraspecific and interspecific interactions. Historically, parasites have often been overlooked in ecological studies, so there are gaps in our understanding of their natural history, and even fundamental information, such as their geographic distribution, is often poorly understood. The distribution of parasites is not consistent throughout their distribution range. Variations in limiting factors, such as precipitation, in an area can influence plant communities in such a way that it creates ecological gradients. Species that can inhabit a variety of habitat types often occur throughout such an ecological gradient. However, the parasites that infect them may differ over the ecological gradient due to being more habitat specific or requiring additional hosts that are habitat specific.

In this thesis, I explored parasite community variations in a sleepy lizard (Tiliqua rugosa) population inhabiting an area with a precipitation-induced ecological gradient, and whether different plant communities from natural vegetation to those more affected by farming can influence these parasite communities. This work is a continuation of a long-established area of exploration of sleepy lizards and their parasites set up by the late Prof. C. Michael Bull who built upon the earlier work by Michael Smyth.

Through the dissection of road kills I confirmed the gastrointestinal helminths that infect lizards in the study site. I caught lizards along established transects in the study site and examined them for the presence of ectoparasites. I also collected blood and faecal samples that were subsequently examined microscopically to determine the prevalence of the various endoparasites in the sleepy lizard population.

Vegetation data were collected from sample plots along two transects that span both disturbed and rehabilitated areas and are therefore representative of the vegetation of the study site. The floristic data was analysed to determine the various plant communities. Based on the identified plant communities, the habitats along the two transects were assigned to different habitat categories.

The geographic distribution of the various identified ecto- and endoparasites were then mapped out within the study site. Sub-samples of the data collected along the two transects used for the vegetation studies were used to identify associations between different parasite species and various habitat categories.

This work has furthered our knowledge on associations between the parasite community of sleepy lizards and different habitats. The variations in the parasite community were mainly driven by differences in the prevalence of ixodid tick species as a result of their association with specific habitat categories. Precipitation as well as disturbances to the habitat influenced the distribution of these ectoparasites, which influences the degree of overlap in their parapatric distribution. The information about the prevalence of the various parasites across the ecological gradient form a basis for future studies, which should focus on filling the gaps in our understanding of the life cycles the parasites, and identifying the ecological roles they play.

Keywords: Amblyomma limbatum, Bothriocroton hydrosauri, Hemolivia mariae, Oochoristica trachysauri, Ophionyssus natricis, Ornithodoros gurneyi, parasites, Thelandros trachysauri, Tiliqua rugosa, parapatric boundary, phytosociology

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2022
School: College of Science and Engineering
Supervisor: Michael G. Gardner