Mosaic metabolic ageing: Basal and standard metabolic rate age in opposite directions and independent of environmental quality, sex and lifespan in a passerine

1. Crucial to our understanding of the ageing process is identifying how traits change with age, which variables alter their ageing process and how these traits associate with fitness. 2. Here we investigated metabolic ageing in outdoor-living captive zebra finches experiencing foraging costs. We longitudinally monitored 407 individuals over six years and collected 3213 measurements of two independent mass-adjusted metabolic traits: basal metabolic rate (BMRm) at thermoneutral temperatures and standard metabolic rate (SMRm), measured as BMRm but at ambient temperatures below thermoneutrality. 3. We define mosaic or asynchronous ageing as the difference in standardized absolute ageing rates between traits, and we estimate the degree of asynchrony using the within-individual correlation of change in trait values with age. 4. BMRm decreased linearly with age, consistent with earlier reports. In contrast, SMRm increased linearly with age. The absolute standardized change with age w...1. 要理解衰老过程，核心在于厘清性状随年龄的变化规律、调控衰老进程的影响变量，以及这些性状与适合度（fitness）之间的关联。 2. 本研究针对存在觅食成本的室外圈养斑胸草雀开展代谢衰老相关研究。我们对407只个体进行了为期6年的纵向监测，共获取3213项针对两种独立体重校正代谢性状的测量数据：热中性温度下的基础代谢率（basal metabolic rate, BMRm），以及在低于热中性温度的环境温度下，以与BMRm相同的测量标准得到的标准代谢率（standard metabolic rate, SMRm）。 3. 本研究将镶嵌式衰老或异步衰老定义为不同性状间标准化绝对衰老速率的差值，并通过性状值随年龄变化的个体内相关性，估算衰老的异步化程度。 4. BMRm随年龄呈线性下降趋势，与此前的研究报道一致。与之相反，SMRm随年龄呈线性上升趋势。随年龄变化的标准化绝对改变量……