Data from: The behavioural consequences of sex reversal in dragons

Sex differences in morphology, physiology, and behaviour are caused by sex-linked genes, as well as by circulating sex-steroid levels. Thus, a shift from genotypic to environmental sex determination may create an organism that exhibits a mixture of male-like and female-like traits. We studied a lizard species (Central Bearded Dragon, Pogona vitticeps), in which the high-temperature incubation of eggs transforms genetically male individuals into functional females. Although they are reproductively female, sex-reversed dragons (individuals with ZZ genotype reversed to female phenotype) resemble genetic males rather than females in morphology (relative tail length), general behaviour (boldness and activity level), and thermoregulatory tactics. Indeed, sex-reversed ‘females’ are more male-like in some behavioural traits than are genetic males. This novel phenotype may impose strong selection on the frequency of sex reversal within natural populations, facilitating rapid shifts in sex-determining systems. A single period of high incubation temperatures (generating thermally induced sex reversal) can produce functionally female individuals with male-like (or novel) traits that enhance individual fitness, allowing the new temperature-dependent sex-determining system to rapidly replace the previous genetically based one.

形态、生理与行为层面的性别差异由伴性基因（sex-linked genes）以及循环性类固醇激素（sex-steroid）水平共同介导。因此，从基因型性别决定（genotypic sex determination）向环境型性别决定（environmental sex determination）的转变，可能会催生兼具雄性样与雌性样特征的生物体。我们以中部鬃狮蜥（Central Bearded Dragon，*Pogona vitticeps*）为研究对象，该物种的卵在高温孵化条件下，其遗传雄性个体可转化为具备生殖功能的雌性个体。尽管这类性逆转个体（基因型为ZZ却表现出雌性表型的个体）在生殖属性上属于雌性，但在形态（相对尾长）、一般行为（大胆程度与活动水平）以及体温调节策略上，它们更接近遗传雄性而非雌性。事实上，在部分行为性状上，性逆转的‘雌性’比遗传雄性更具雄性特征。这种全新的表型可能会对自然种群中性逆转事件的频率施加强烈选择压力，进而推动性别决定系统的快速转变。仅需一段时期的高温孵化环境（可诱导产生热诱导性逆转（thermally induced sex reversal）），即可诞生兼具雄性样（或全新）性状的功能性雌性个体，这类个体的个体适合度（individual fitness）得以提升，从而使新的温度依赖型性别决定系统（temperature-dependent sex-determining system）能够快速取代原有的遗传型性别决定系统。