Aberdeen Centre for Environmental Sustainability (ACES), University of Aberdeen, School of Biological Sciences, Aberdeen, UK.
J Evol Biol. 2010 May;23(5):902-13. doi: 10.1111/j.1420-9101.2010.01956.x.
Testosterone underlies the expression of most secondary sexual traits, playing a key role in sexual selection. However, high levels might be associated with physiological costs, such as immunosuppression. Immunostimulant carotenoids underpin the expression of many red-yellow ornaments, but are regulated by testosterone and constrained by parasites. We manipulated testosterone and nematode burdens in red grouse (Lagopus lagopus scoticus) in two populations to tease apart their effects on carotenoid levels, ornament size and colouration in three time-step periods. We found no evidence for interactive effects of testosterone and parasites on ornament size and colouration. We showed that ornament colouration was testosterone-driven. However, parasites decreased comb size with a time delay and testosterone increased carotenoid levels in one of the populations. This suggests that environmental context plays a key role in determining how individuals resolve the trade-off between allocating carotenoids for ornamental coloration or for self-maintenance needs. Our study advocates that adequately testing the mechanisms behind the production or maintenance of secondary sexual characters has to take into account the dynamics of sexual trait expression and their environmental context.
睾酮是大多数第二性征表达的基础，在性选择中起着关键作用。然而，高水平的睾酮可能与生理成本有关，如免疫抑制。免疫刺激类胡萝卜素是许多红黄装饰物表达的基础，但受睾酮调节，并受到寄生虫的限制。我们在两个红松鸡（Lagopus lagopus scoticus）种群中操纵睾酮和线虫负担，以在三个时间阶段分别研究它们对类胡萝卜素水平、装饰物大小和颜色的影响。我们没有发现睾酮和寄生虫对装饰物大小和颜色的相互作用的证据。我们表明，装饰物的颜色是由睾酮驱动的。然而，寄生虫会延迟降低鸡冠的大小，而在一个种群中，睾酮会增加类胡萝卜素的水平。这表明环境背景在决定个体如何解决将类胡萝卜素分配给装饰性颜色或自我维持需求的权衡方面起着关键作用。我们的研究主张，充分测试第二性特征的产生或维持机制，必须考虑到性特征表达的动态及其环境背景。
