Macquarie University
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Behavioural and biological responses of Australian water dragons (Intellagama lesueurii) to urbanization

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posted on 2022-03-28, 12:47 authored by James H. Baxter-Gilbert
One of the strongest driving forces of evolution is environmental change. Within the modern era, some of the most rapid environmental change has occurred as a result of urbanisation. As such, recent research aims to understand how species are adapting to urban landscapes (urban evolution) and how natural selection is operating in unnatural environments (anthropic selection). This goal was the cornerstone of my thesis research, using Australian water dragons (Intellagama lesueurii) to examine how the selective forces within urban environments may shape their natural histories and alter their evolutionary trajectory. I took a multidisciplinary approach to explore water dragon urban evolution, by examining traits related to their behavioural ecology (social interactions and spatial organisation, behavioural traits, and innate antipredator responses; Chapters I, II, & III respectively), morphology (body length and size; Chapter IV), and physiology (performance capacity; Chapters V & VI), using both field observations and laboratory experiments. The basis of most of this thesis' research involved contrasting traits of lizards living in, or originating from, populations varying in their levels of urbanisation (urban, semi-natural, and natural). I also examined the mechanisms that may have caused urban-derived divergence of morphological and behavioural traits (i.e., heritable traits vs phenotypic plasticity). My research identified several urban-derived divergent phenotypes, including increased rates of aggressive encounters, increased boldness, decreased body size paired with increased limb and head size, and decreased endurance capacity. My research also identified that both divergent behavioural (boldness) and morphological (body length and size) traits have a genetic origin, suggesting they are heritable and may be adaptive. Overall, this thesis provides insight into the urban evolution of water dragons in the Sydney region, and provides a framework for using a multidisciplinary approach to rigorously examine mechanistic urban ecology and evolution.


Table of Contents

1. Street fighters: bite force, injury rates and population density of urban Australian water dragons (Intellagama lesueurii) -- 2. Bold new world: urbanisation selects for boldness in a lizard -- 3. Runners and fighters: clutch effects and body size drive innate antipredator behaviour in hatchling lizards -- 4. Anthropic selection: human-altered landscapes drive the development of divergent morphology in an urbanised lizard -- 5. Comparability and repeatability of three commonly used methods for measuring endurance capacity -- 6. Running through the concrete jungle: performance capacity and trade-offs in an urban-living lizard.


Theoretical thesis. Thesis by publication. Includes bibliographical references

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science and Engineering, Department of Biological Sciences

Department, Centre or School

Department of Biological Sciences

Year of Award


Principal Supervisor

Martin Whiting


Copyright James Harrison Baxter-Gilbert 2018. Copyright disclaimer:




1 online resource (188 pages : illustrations, maps)

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