Colour takes on diverse forms and serves important, versatile functions in the lives of animals. Consequently, animal colouration is influenced by various physiological, ecological and evolutionary factors. Members of the family Agamidae are known to use their elaborate colouration in contexts like courtship, competition, camouflage, and thermoregulation. Some species are also able to actively modulate and change the expression of their colours in response to shifting contexts. However, this fascinating group of colourful lizards, especially species found in India, remains poorly studied. This thesis aims to uncover the factors that influence the form and function of colours in agamids.
Even well-intentioned conservation efforts can have unintended consequences. In my first chapter, I study how vulture restaurants can have a cascading effect on the physiology, colour, and morphology of the vulnerable Indian spiny tailed lizard (Saara hardwickii) by inadvertently increasing its exposure to predators.
Did you know that CES’s most popular study organism, Psammophilus dorsalis, engages in colourful sleeptalking at night?! In my second chapter, I investigate why P. dorsalis expresses social colours at night in the absence of any obvious stimulus or social context. I test whether diurnal social interactions influence the nocturnal expression of social colours in this species.
Scaling up from these species-centric studies, my third chapter explores the evolution of colours in Asian and African agamids using a phylogenetic comparative approach. I will test the contribution of ecological factors such as habitat openness, microhabitat substrates and habit in shaping the evolution of colours on different body regions of species in these clades.
While most agamids are content with having a fixed set of colours, some Indian species love to change their colourful costumes as the occasion demands. In my final chapter, I explore the evolutionary drivers behind rapid colour change in Indian agamids and quantify its spectral extent. I also investigate the thermoregulatory trade-offs associated with expression of social colouration in these species.
Overall, this thesis will help unravel various intricacies of colour evolution and highlight the intriguing role it plays in the lives of agamids.