Phylogeographic structure, demographic history and morph composition in a colour polymorphic lizard.

Area of Science:

• Evolutionary Biology
• Herpetology
• Population Genetics

Background:

• Polymorphism in species can drive population divergence and speciation.
• The tawny dragon lizard (Ctenophorus decresii) exhibits geographic variation in male throat coloration.

Purpose of the Study:

• To assess the relationship between geographic variation in male throat colour polymorphism and phylogeographic structure in Ctenophorus decresii.
• To investigate the evolutionary history of colour polymorphism within the Ctenophorus decresii species complex.

Main Methods:

• Phylogeographic analysis of genetic variation across different regions.
• Assessment of morph composition and frequency in polymorphic and monomorphic populations.
• Examination of genetic divergence and gene flow between lineages.

Main Results:

• Four genetically distinct lineages were identified, including polymorphic and monomorphic populations.
• Divergence patterns suggest isolation in Pleistocene refugia.
• Colour polymorphism likely evolved once, with subsequent loss in some lineages, or evolved independently twice.
• Evidence of limited admixture in a contact zone without intermediate phenotypes suggests incipient speciation.

Conclusions:

• Geographic variation in colour polymorphism is linked to phylogeographic structure in Ctenophorus decresii.
• Barriers to gene flow between lineages with differing morph compositions indicate ongoing speciation.
• The evolutionary history of colour polymorphism may involve a single origin with subsequent losses or multiple independent origins.