Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Horm Behav. 2013 May;63(5):782-90. doi: 10.1016/j.yhbeh.2013.03.005. Epub 2013 Mar 19.
Testosterone (T) is often referred to as the "male hormone," but it can influence aggression, parental behavior, and immune function in both males and females. By experimentally relating hormone-induced changes in phenotype to fitness, it is possible to ask whether existing phenotypes perform better or worse than alternative phenotypes, and hence to predict how selection might act on a novel or rare phenotype. In a songbird, the dark-eyed junco (Junco hyemalis), we have examined the effects of experimentally elevated T in females on fitness-related behaviors such as parental care. In this study, we implanted female juncos with exogenous T and examined its effect on fitness (survival, reproduction, and extra-pair mating) to assess whether T-altered phenotypes would prove to be adaptive or deleterious for females. Experimental elevation of T decreased the likelihood that a female would breed successfully, and T-implanted females had lower total reproductive success at every stage of the reproductive cycle. They did not, however, differ from control females in fledgling quality, extra-pair offspring production, survival, or reproduction in the following year. Previous work in this system has shown that experimental elevation of T in males alters behavior and physiology and decreases survival but increases the production of extra-pair offspring, leading to higher net fitness relative to control animals. Our results suggest that increased T has divergent effects on male and female fitness in this species, and that prevailing levels in females may be adaptive for them. These findings are consistent with sexual conflict.
睾酮（T）通常被称为“男性荷尔蒙”，但它也会影响男性和女性的攻击性、亲代行为和免疫功能。通过将激素诱导的表型变化与适应性相关联的实验，可以询问现有表型是否比替代表型表现更好或更差，从而预测选择可能对新的或罕见的表型产生什么作用。在一种鸣禽——暗眼灯草鹀（Junco hyemalis）中，我们研究了实验升高雌性激素 T 对亲代照顾等与适应性相关的行为的影响。在这项研究中，我们给雌性暗眼灯草鹀植入外源性 T，并观察其对适应性（存活率、繁殖和婚外交配）的影响，以评估 T 改变的表型对雌性来说是适应性的还是有害的。T 的实验升高降低了雌性成功繁殖的可能性，而且 T 植入的雌性在繁殖周期的每个阶段的总繁殖成功率都较低。然而，它们在雏鸟质量、婚外繁殖后代的产生、存活率或次年的繁殖方面与对照雌性没有差异。该系统之前的研究表明，实验升高雄性的 T 会改变行为和生理，降低存活率，但会增加婚外繁殖后代的产生，从而使净适应性相对于对照动物更高。我们的研究结果表明，在这个物种中，T 对雄性和雌性的适应性有不同的影响，而雌性的普遍水平可能对它们是适应性的。这些发现与性冲突一致。
