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

Abstract

In polymorphic species, population divergence in morph composition and frequency has the potential to promote speciation. We assessed the relationship between geographic variation in male throat colour polymorphism and phylogeographic structure in the tawny dragon lizard, Ctenophorus decresii. We identified four genetically distinct lineages, corresponding to two polymorphic lineages in the Northern Flinders Ranges and Southern Flinders Ranges/Olary Ranges regions respectively, and a monomorphic lineage in the Mt Lofty Ranges/Kangaroo Island region. The degree of divergence between these three lineages was consistent with isolation to multiple refugia during Pleistocene glacial cycles, whereas a fourth, deeply divergent (at the interspecific level) and monomorphic lineage was restricted to western New South Wales. The same four morphs occurred in both polymorphic lineages, although populations exhibited considerable variation in the frequency of morphs. By contrast, male throat coloration in the monomorphic lineages differed from each other and from the polymorphic lineages. Our results suggest that colour polymorphism has evolved once in the C. decresii species complex, with subsequent loss of polymorphism in the Mt Lofty Ranges/Kangaroo Island lineage. However, an equally parsimonious scenario, that polymorphism arose independently twice within C. decresii, could not be ruled out. We also detected evidence of a narrow contact zone with limited genotypic admixture between the polymorphic Olary Ranges and monomorphic Mt Lofty Ranges regions, yet no individuals of intermediate colour phenotype. Such genetic divergence and evidence for barriers to gene flow between lineages suggest incipient speciation between populations that differ in morph composition.

Spectral sensitivity of cone photoreceptors and opsin expression in two colour-divergent lineages of the lizardCtenophorus decresii

“…Male throat coloration differs between the two lineages, whereas female throats are cream in both lineages (McLean et al, 2014a). All populations from the northern lineage are polymorphic, with four co-occurring, discrete male throat colours (orange, yellow, grey and a central orange patch surrounded by yellow) (Teasdale et al, 2013).…”

The genetic basis of discrete and quantitative colour variation in the polymorphic lizard, Ctenophorus decresii

“…Genomic DNA was extracted from red blood cells with proteinase-K and a GenCatch Blood and Tissue Genomic Mini-Prep Kit (Epoch Life Science, TX, USA). DNA samples were PCR amplified at eight microsatellite loci previously developed for C. decresii (Ctde03, Ctde05, Ctde08, Ctde12, Ctde21 and Ctde45; [38, 45]), or for the closely related Ctenophorus pictus ([CP10 and CP11; [46]), using published PCR protocols [38]. Amplified PCR products were sent to Macrogen (Korea) for fragment visualisation, and fragment sizes were called using Peak Scanner ver.…”

“…Within each morph category, the size of the colour patch and patterning varies substantially among individuals (Fig. 1; [34, 37, 38]). The colour morphs in Northern C. decresii correspond to different behavioural strategies [39].…”

Has contemporary climate change played a role in population declines of the lizard Ctenophorus decresii from semi-arid Australia?

“…However, since that time no sightings have been made in this region despite repeated surveys (Table S1). The apparent absence of C. decresii in the northern Flinders Ranges contrasts sharply with the remainder of its range, where it is locally abundant in suitable habitat (McLean, 2014;McLean et al, 2014). The species is conspicuous, with the colour polymorphic males having brightly coloured throats and defending territories from prominent rock perches.…”