Oral Presentation 64th International Conference of the Wildlife Disease Association 2015

Have pathogens influenced the evolution of non-carotenoid colouration in dragon lizards? (#62)

Jessica Hacking 1 , Michael Gardner 1
  1. Flinders University, Adelaide, SA, Australia
Pathogens can drive wildlife evolution in many ways. For example, pathogens can cause severe population bottlenecks, and they have played key roles in speciation events and the evolution of sociality. Pathogens can also drive the evolution of colouration through sexual selection. This phenomenon has been widely studied in carotenoid-based colouration systems but less is known about the roles of the other pigment types present in vertebrates: pteridines and melanins. These pigments differ in how they are acquired and produced; carotenoids are acquired from the diet and pteridines and melanins are endogenously produced from purines and tyrosine, respectively. The link between pathogens and carotenoid-based colouration is well understood, with carotenoid intake determined by foraging ability, which in turn is influenced by pathogen load. In contrast, much less is known about the relationship between pteridine- and melanin-based colouration and pathogens. Conflicting results have been reported with regards to associations between non-carotenoid colouration and pathogens, and the suggestion of a link between pteridine- and melanin-based pigments and the immune system is controversial. We propose to examine whether pathogen load is associated with secondary sexual colouration in the tawny dragon (Ctenophorus decresii). The tawny dragon is a small (<30g) agamid that inhabits rocky outcrops and ranges within South Australia and uses pteridine- and melanin-based colour patches in male-male confrontation and mate acquisition displays. We will quantify colouration variation independently of the human visual system using photograph-derived data. Pathogens will be identified, and pathogen load will be determined, using morphological and molecular methods. Little is known about the pathogens infecting tawny dragons. However, preliminary results show individual variation in the abundance of ticks, mites and haemogregarine blood parasites. This research will aid in understanding the role that pathogens play in the evolution of secondary sexual colouration in an agamid pteridine- and melanin-based colour system.