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

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.

在多态性物种（polymorphic species）中，种群在形态组成与频率上的分化具备推动物种形成的潜力。我们针对德氏岩龙蜥（*Ctenophorus decresii*，俗称棕澳蜥（tawny dragon lizard））开展研究，分析雄性喉部颜色多态性（colour polymorphism）的地理变异与其系统地理结构（phylogeographic structure）之间的关联。我们共鉴定出4个遗传分化显著的支系：分别为分布于北弗林德斯山脉、南弗林德斯山脉/奥拉里山脉区域的2个多态支系，以及分布于洛夫蒂山脉/袋鼠岛区域的1个单态支系（monomorphic lineage）。这3个支系间的分化程度与更新世（Pleistocene）冰期时期多个避难所（refugia）的隔离模式相符；而第4个支系则是分化程度极深（达到种间级别（interspecific level））的单态支系，仅分布于新南威尔士州西部。两个多态支系均存在相同的4种喉部形态，不过不同种群间的形态频率存在显著差异。与之形成对比的是，单态支系的雄性喉部颜色不仅彼此存在差异，也与多态支系的喉部颜色截然不同。我们的研究结果表明，德氏岩龙蜥物种复合群（species complex）的颜色多态性仅起源过一次，随后洛夫蒂山脉/袋鼠岛支系丢失了多态性。不过，另一种同样符合演化简约性原则的假说——即颜色多态性在德氏岩龙蜥中独立起源了两次——无法被排除。我们还在多态的奥拉里山脉区域与单态的洛夫蒂山脉区域之间，发现了一处狭窄的接触带：该区域存在有限的基因型混合（genotypic admixture），但未观察到具有中间颜色表型的个体。上述遗传分化以及支系间存在基因流（gene flow）障碍的证据，表明在形态组成存在差异的种群之间，正处于初期物种形成（incipient speciation）的过程中。