Rankin Katrina J, McLean Claire A, Kemp Darrell J, Stuart-Fox Devi
School of BioSciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
Department of Sciences, Museum Victoria, Carlton Gardens, VIC, 3053, Australia.
BMC Evol Biol. 2016 Sep 6;16:179. doi: 10.1186/s12862-016-0757-2.
Colour polymorphic species provide invaluable insight into processes that generate and maintain intra-specific variation. Despite an increasing understanding of the genetic basis of discrete morphs, sources of colour variation within morphs remain poorly understood. Here we use the polymorphic tawny dragon lizard Ctenophorus decresii to test simple Mendelian models for the inheritance of discrete morphs, and to investigate the genetic basis of continuous variation among individuals across morphs. Males of this species express either orange, yellow, orange surrounded by yellow, or grey throats. Although four discrete morphs are recognised, the extent of orange and yellow varies greatly. We artificially elevated testosterone in F0 females and F1 juveniles to induce them to express the male throat colour polymorphism, and quantified colour variation across the pedigree.
Inheritance of discrete morphs in C. decresii best fit a model whereby two autosomal loci with complete dominance respectively determine the presence of orange and yellow. However, a single locus model with three co-dominant alleles for orange, yellow and grey could not be definitively rejected. Additionally, quantitative expression of the proportion of orange and yellow on the throat was strongly heritable (orange: h(2) = 0.84 ± 0.14; yellow: h(2) = 0.67 ± 0.19), with some evidence for covariance between the two.
Our study supports the theoretical prediction that polymorphism should be governed by few genes of major effect, but implies broader genetic influence on variation in constituent morph traits.
颜色多态性物种为研究产生和维持种内变异的过程提供了宝贵的见解。尽管人们对离散形态的遗传基础有了越来越多的了解，但形态内颜色变异的来源仍知之甚少。在这里，我们使用多态性茶色龙蜥（Ctenophorus decresii）来测试离散形态遗传的简单孟德尔模型，并研究不同形态个体间连续变异的遗传基础。该物种的雄性表现出橙色、黄色、橙色周围环绕着黄色或灰色的喉部。尽管识别出了四种离散形态，但橙色和黄色的程度差异很大。我们人为提高了F0雌性和F1幼体的睾酮水平，以诱导它们表现出雄性喉部颜色多态性，并对整个谱系中的颜色变异进行了量化。
茶色龙蜥离散形态的遗传最符合一个模型，即两个具有完全显性的常染色体位点分别决定橙色和黄色的存在。然而，一个具有橙色、黄色和灰色三个共显性等位基因的单基因座模型也不能被明确排除。此外，喉部橙色和黄色比例的定量表达具有很强的遗传性（橙色：h(2) = 0.84 ± 0.14；黄色：h(2) = 0.67 ± 0.19），并且有证据表明两者之间存在协方差。
我们的研究支持了理论预测，即多态性应由少数主效基因控制，但这意味着对组成形态特征变异有更广泛的遗传影响。
