Year

2023

Degree Name

Bachelor of Conservation Biology (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Christopher Friesen

Abstract

Response to colour stimuli within the animal kingdom is responsible for the evolution of many different visual ornaments across a range of species. Within many species males and females utilise colourful patterns and plumages to attract the attention of a mate, warn predators of toxicity and signal body condition and genetic prowess. However, the creation and maintenance of pigments by animals is not a simple task with a variety of types of pigment-producing cells such as melanophores, iridophores and xanthophores, capable of producing a wide range of pigments and iridescent shines. How colour is perceived by surrounding individuals also affects the signal that colouration conveys. Due to the high level of importance that colour has in signalling, many species have developed multiple different coloured phenotypes within the overall population. The presence of these colour polyphenisms and the potentially correlated traits is an area of intrigue within this study. As such, this thesis aimed to investigate the relationship between colour polymorphisms and potential surrounding environmental and physiological influences. The study was conducted using a species of dragon found throughout southern and central Australia, Ctenophorus pictus. This small lizard comes in a variety of colour morphs each with proven associated physical traits. This study aimed to investigate patterns in head colouration, chest and bib colouration, and their relationship to environmental and physiological traits. Chapter 2: Images were collected from 2015-2022 across many known populations of C. pictus, these images were then imported into image analysis software, ImageJ, and the colouration of each male was quantified using two common colour visualisation systems, red, green, and blue colour levels, followed by hue, saturation, and brightness levels. We statistically compared these colour indicators to a selection of potential environmental influences, latitude, and longitude. Additionally, we selected factors that pose a potential physiological influence on the ability of an individual to display colouration, body condition and snout-vent length, and statistically compared the colour indicators to these variables. We ran these tests on data collected from the head colouration of males, as well as their yellow gular patches, better known as bibs, and black central chest patches. The data | 6790240 iii revealed significant correlations between the hue of head colour and longitude, with individuals presenting more variety of head colours in the eastern populations. Furthermore, head colours were also brighter towards the east as well, potentially indicating higher quality habitat or greater natural selection for more head colours. Analysis of the yellow bib revealed that the hue of yellow remained the same throughout all populations, yet both brightness and saturation of the bib were affected by latitude. Animals towards the south were more saturated in their yellow pigment but the yellow pigment of individuals in the north was brighter, perhaps due to female-mediated mate choice selecting individuals with brighter colour in the north or more saturated colour in the south. Once again, these results indicate that there may be an environmental influence on the male’s ability to produce the pigment, but it may also be controlled by natural or female-mediated mate selection. Finally, the results from the analysis of the black chest patch indicate that the patch saturation and hue changed depending on population location.

FoR codes (2020)

310403 Biological adaptation, 310907 Animal physiological ecology

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.