Variation in testosterone and corticosterone in amphibians and reptiles: relationships with latitude, elevation, and breeding season length

Latitudinal variation in life history traits has been the focus of numerous investigations, but underlying hormonal mechanisms have received much less attention. Steroid hormones play a central role in vertebrate reproduction and may be associated with life-history trade-offs. As such, circulating concentrations of these hormones vary tremendously across vertebrates, yet inter-specific geographic variation in male hormone concentrations has only been studied in detail in birds. We here report on such variation in amphibians and reptiles, confirming patterns observed in birds. Using phylogenetic comparative analyses, we found that in amphibians, but not reptiles, testosterone and baseline corticosterone were positively related to latitude. Baseline corticosterone was negatively related to elevation in amphibians, but not reptiles. For both groups, testosterone concentrations were negatively related with breeding season length. Additionally, testosterone concentrations were positively cor...

生活史性状的纬度梯度变异长期以来是诸多研究的核心议题，但其背后的激素调控机制却鲜有深入探讨。类固醇激素（steroid hormones）在脊椎动物繁殖过程中发挥核心调控作用，且可能与生活史权衡（life-history trade-offs）现象存在关联。尽管此类激素的循环浓度在脊椎动物类群间差异显著，但目前仅在鸟类中对雄性激素浓度的种间地理变异开展了详尽研究。本研究针对两栖类与爬行类展开此类变异的调查，验证了此前在鸟类中发现的相关模式。本研究采用系统发育比较分析（phylogenetic comparative analyses）方法，结果显示：在两栖类中，睾酮（testosterone）与基础皮质酮（baseline corticosterone）均与纬度呈正相关关系，而爬行类未呈现此规律；基础皮质酮水平在两栖类中与海拔呈负相关关系，爬行类则无此关联。两类群的睾酮浓度均与繁殖季长度呈负相关。此外，睾酮浓度与……呈正相关