Data from: Female anoles retain responsiveness to testosterone despite the evolution of androgen-mediated sexual dimorphism

1. The evolution of sexual dimorphism presents a challenge because males and females must express two phenotypes from the same underlying genome. In vertebrates, one solution to this challenge is to link the expression of shared traits to sex steroids. However, even ‘male-biased’ steroids such as testosterone (T) circulate at biologically significant levels in females, raising the question of whether sexual dimorphism evolves not only through the coupling of trait expression to T in males, but also through the decoupling of trait expression from T in females. 2. We tested these alternatives by asking whether male and female brown anoles (Anolis sagrei) respond to exogenous T in similar fashion with respect to a suite of sexually dimorphic traits: growth, skeletal morphology, resting metabolism, fat storage, dewlap size and dewlap colour. 3. First, we established the ontogeny of sexual dimorphism in a colony raised in a laboratory common garden. Next, we treated juveniles of each sex with either T implants or empty implants at 5–8 months of age, when sexual dimorphism first began to develop for most traits. 4. T stimulated growth in both sexes and largely abolished natural sex differences in growth. This effect was associated with the stimulation of resting metabolism and the diversion of energy from fat and liver stores in both sexes. T also enlarged the dewlap in both sexes, though females never developed dewlaps equal in size to those of males. Finally, T altered the brightness and saturation of the dewlap in both sexes, inducing coloration similar to that of adult males. 5. Female brown anoles retain many of the same tissue-specific responses to T that occur in males, suggesting that the evolution of androgen-mediated sexual dimorphism has been achieved largely through the coupling of trait expression to sex differences in circulating T, without an associated decoupling of trait expression from T in females.

1. 性二态性（sexual dimorphism）的演化是一项极具挑战性的课题，原因在于雄性与雌性需从同一套基础基因组中表达两种迥异的表型。在脊椎动物中，应对这一挑战的经典策略是将共享性状的表达与性类固醇（sex steroids）相绑定。然而，即便如睾酮（testosterone, T）这类“雄性偏向”的类固醇激素，在雌性体内也能达到具有生物学意义的循环浓度，这引发了一个关键问题：性二态性的演化是否不仅通过雄性的性状表达与睾酮的耦合机制实现，还通过雌性的性状表达脱离睾酮的解偶联过程达成？
2. 我们通过检验雄性与雌性棕安乐蜥（Anolis sagrei）对睾酮（T）外源施加的响应，在一系列性二态性状上是否表现出相似模式，来验证上述两种假说：这些性状涵盖生长、骨骼形态、静息代谢、脂肪储存、喉垂（dewlap）大小与喉垂颜色。
3. 首先，我们在实验室统一饲养环境的种群中，确立了性二态性的个体发生轨迹。随后，在大多数性状首次开始出现性二态的5至8月龄阶段，我们为每个性别的幼体分别植入睾酮缓释植入物或空白对照植入物。
4. 睾酮在两个性别中均能促进生长，并基本消除了生长的自然性别差异。该效应与两个性别的静息代谢被激活、能量从脂肪与肝脏储存中转移的现象相关联。睾酮同样能扩大两个性别的喉垂尺寸，尽管雌性的喉垂尺寸始终无法达到雄性水平。最后，睾酮改变了两个性别的喉垂亮度与饱和度，使其着色模式与成年雄性相似。
5. 雌性棕安乐蜥保留了与雄性一致的多种组织特异性睾酮响应，这表明雄激素介导的性二态性演化主要通过将性状表达与循环睾酮的性别差异相耦合实现，而无需伴随雌性性状表达脱离睾酮的解偶联过程。