生活史理论预测,生殖投资与自我维持是取舍的。端粒,染色体末端的保护帽,为评估生活史的权衡提供了一个有希望的途径,因为它们对压力的反应会缩短,并且可以预测剩余的寿命。在男性中,睾丸激素经常介导生活史的权衡,在某种程度上,通过它对性装饰的影响,这是生殖投资的一个重要方面。然而,关于端粒动力学与性装饰之间个体内关联的研究数量有限,结果参差不齐.此外,大多数这样的研究都是观察性的,很难辨别任何因果关系的性质。为了解决这个问题,我们在自由生活的男性高超仙女(Maluruscyaneus)中使用了短效睾丸激素植入物,以刺激性装饰品的产生:早期蜕皮成昂贵的蓝色繁殖羽毛。我们没有发现睾丸激素升高的证据,随之而来的早期蜕皮变成繁殖羽毛,加速端粒缩短。因此,我们进行了系统评价和两项荟萃分析(28项研究,54个效应大小)探索端粒与(1)睾丸激素和(2)性装饰之间的关联。根据我们的实验结果,荟萃分析均未显示睾丸激素或性装饰与端粒长度或端粒动力学的总体相关性。然而,元回归表明,实验性的,与观测相比,研究报告了更多的权衡取舍证据。我们的荟萃分析强调需要进一步的实验研究,以更好地了解端粒长度或端粒动力学对睾丸激素或性装饰的潜在反应。
Life-history theory predicts that reproductive investments are traded-off against self-maintenance. Telomeres, the protective caps on the ends of chromosomes, offer a promising avenue for assessing life-history trade-offs, as they shorten in response to stressors and are predictive of the remaining lifespan. In males, testosterone frequently mediates life-history trade-offs, in part, through its effects on sexual ornamentation, which is an important aspect of reproductive investment. However, studies of within-individual associations between telomere dynamics and sexual ornamentation are limited in number and have produced mixed results. Furthermore, most such studies have been observational, making it difficult to discern the nature of any causal relationship. To address this, we used short-acting testosterone implants in free-living male superb fairy-wrens (Malurus cyaneus) to stimulate the production of a sexual ornament: early moult into a costly blue breeding plumage. We found no evidence that elevated testosterone, and the consequent earlier moult into breeding plumage, accelerated telomere shortening. We therefore followed up with a systematic review and two meta-analyses (28 studies, 54 effect sizes) exploring the associations between telomeres and (1) testosterone and (2) sexual ornamentation. In line with our experimental findings, neither meta-analysis showed an overall correlation of testosterone or sexual ornamentation with telomere length or telomere dynamics. However, meta-regression showed that experimental, compared to observational, studies reported greater evidence of trade-offs. Our meta-analyses highlight the need for further experimental studies to better understand potential responses of telomere length or telomere dynamics to testosterone or sexual ornamentation.