The Evolution of Diversity: Sexual selection and natural selection on the social signals of gliding lizards.

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Copyright: Klomp, Danielle Alice
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Abstract
Diversity in animal colour and form can often be attributed to communication signals, which play an important role in species recognition and mate choice. Divergence of signals among populations is therefore thought to be a driver of speciation. This thesis examines signalling processes in the species rich agamid genus, Draco, to understand their influence on signal design, signal divergence and ultimately speciation. Draco lizards are known as ‘gliding lizards’, as they have retractable gliding membranes. They communicate with extendable throat-fans, called dewlaps, which are diverse in colour, shape and size among species. Chapter two assesses the importance of dewlap signal design for detection and recognition in Draco melanopogon, by presenting free-living lizards with robots displaying dewlaps of different designs. Dewlap design does not affect the latency of signal detection by conspecifics, but once the robot dewlap had been detected, males responded with greater intensity to dewlaps that best resembled the species’ typical design, suggesting pattern is important in species recognition. As signal components may evolve differently in populations exposed to different selection pressures, chapter three assess the relationships between the dewlap components (colour and size) and aspects of their environments. Males of different species employ colour contrast and dewlap size as alternative strategies for effective communication, and predation intensity may play a role in which strategy a species employs. Further, correlations between male dewlap components and sexual dimorphism suggest that sexual selection is also a major factor influencing dewlap design. Chapter four shows that the different gliding membrane colouration of two populations of Draco cornutus closely match the colours of freshly fallen leaves in their respective habitats as they appear to the visual system of predatory birds. This suggests the populations have diverged in colouration to mimic the colours of local falling leaves and thereby reduce predation by birds. Chapter five tests whether Draco sumatranus lizards use their position relative to the sun to enhance the transmission of light through the dewlap, and thus the apparent brightness of their dewlap during display. Lizards are significantly more likely to orientate themselves perpendicular to the sun when displaying, ensuring maximum sun exposure for the extended dewlap. This thesis confirms the centrality of sexual selection, species recognition and predation as major factors influencing signal design in Draco, and thereby furthers our understanding of the evolution of ornament diversity.
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Author(s)
Klomp, Danielle Alice
Supervisor(s)
Ord, Terry
Stuart-Fox, Devi
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Publication Year
2016
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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