Data from: The active metabolic rate predicts a male spider’s proximity to females and expected fitness

Conspicuous traits, such as weaponry and body size, are often correlated with fitness. By contrast, we understand less about how inconspicuous physiological traits affect fitness. Not only is linking physiology directly to fitness a challenge, but in addition, behavioural studies most often focus on resting or basal metabolic rates, resulting in a poor understanding of how active metabolic rates affect fitness. Here we use the golden orb-web spider (Nephila plumipes), a species for which proximity to a female on the web predicts a male's paternity share, to examine the role of resting and active metabolic rates in fitness. Using a semi-natural experimental set-up, we show that males closer to a female have higher active metabolic rates than males further from females. This higher metabolic activity is paralleled by increased citrate synthase activity, suggesting greater mitochondrial densities. Our results link both higher active metabolic rates and increased citrate synthase activity with fitness. Coupled with the behaviour and life history of N. plumipes, these results provide insight into the evolution of physiological systems.

诸如武器结构与体型大小等显性性状，往往与进化适合度（fitness）存在关联。与之相对，学界对于隐性生理性状如何影响进化适合度的认知仍相对有限。不仅直接将生理机能与进化适合度挂钩极具挑战，此外行为学研究大多聚焦于静息代谢率或基础代谢率，导致学界对活动代谢率如何影响适合度的认知仍存在明显缺口。本研究以金园蛛（Nephila plumipes）为研究对象——该物种中，雄蛛在蛛网内靠近雌蛛的距离可预测其获得的父权份额——以此探究静息代谢率与活动代谢率在进化适合度中的作用。通过半自然实验设置，我们发现相较于远离雌蛛的雄蛛，靠近雌蛛的雄蛛具有更高的活动代谢率。这种更高的代谢活性同时伴随柠檬酸合酶（citrate synthase）活性的提升，提示雄蛛拥有更高的线粒体密度。本研究结果证实，更高的活动代谢率与柠檬酸合酶活性提升均与进化适合度相关联。结合金园蛛的行为与生活史特征，本研究结果为生理系统的演化研究提供了新的见解。