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.在多态物种（polymorphic species）中，种群在形态组成与频率上的分化，有可能推动物种形成（speciation）进程。本研究以德氏岩龙蜥（Ctenophorus decresii）为研究对象，评估了雄性喉部颜色多态性的地理变异与系统地理结构（phylogeographic structure）之间的关联。本研究共鉴定出4个遗传分化显著的支系：分别为分布于弗林德斯山脉北段、弗林德斯山脉南段/奥拉里山脉（Olary Ranges）区域的2个多态支系，以及分布于洛夫蒂山脉/袋鼠岛（Kangaroo Island）区域的1个单态支系。这3个支系间的分化程度，与更新世冰期（Pleistocene glacial cycles）中种群隔离至多个避难所的演化模式相符；而第四个支系则为分化程度极深（达到种间水平）的单态支系，其分布仅局限于新南威尔士州西部。两个多态支系均存在相同的4种形态，但不同种群间的形态频率存在显著差异。与之形成对比的是，两个单态支系的雄性喉部色彩不仅彼此存在差异，也与多态支系的雄性喉部色彩截然不同。研究结果表明，德氏岩龙蜥复合种（C. decresii species complex）的颜色多态性仅起源过一次，随后洛夫蒂山脉/袋鼠岛支系丢失了这一多态性。但我们无法排除另一种同样简约的演化假说：即颜色多态性在德氏岩龙蜥类群中独立起源了两次。我们还发现，在多态的奥拉里山脉区域与单态的洛夫蒂山脉区域之间，存在一处狭窄的接触带，该区域内的基因型混合程度有限，但未发现具有中间色彩表型的个体。这类遗传分化以及支系间存在基因流障碍的证据，表明在形态组成存在差异的种群之间，正处于物种形成的初期阶段。