Selection on dispersal drives evolution of metabolic capacities for energy production in female wing‐polymorphic sand field crickets, Gryllus firmus

Life history and metabolism covary, but the mechanisms and individual traits responsible for these linkages remain unresolved. Dispersal capability is a critical component of life history that is constrained by metabolic capacities for energy production. Conflicting relationships between metabolism and life histories may be explained by accounting for variation in dispersal and maximal metabolic rates. We used female wing-polymorphic sand field crickets, Gryllus firmus, selected either for long wings (LW) and flight-capability or short wings (SW) and high early lifetime fecundity to test the hypothesis that selection on dispersal capability drives the evolution of metabolic capacities. While resting metabolic rates were similar, long-winged crickets reached higher maximal metabolic rates than short-winged crickets, resulting in improved running performance. We further provided insight into the mechanisms responsible for covariation between life history and metabolism by comparing mitochondrial content of tissues involved in powering locomotion and assessing function of mitochondria isolated from long- and short-winged crickets. Our results demonstrated that larger metabolic capacities in long-winged crickets were underpinned by increases in mitochondrial content of dorsoventral flight muscle and enhanced bioenergetic capacities of mitochondria within the fat body, a tissue responsible for fuel storage and mobilization. Thus, selection on flight-capability remodels metabolism in a trait and tissue-specific manner to enlarge metabolic capacities necessary for dispersal.

生活史（life history）与新陈代谢（metabolism）存在协变关系，但介导二者关联的具体机制与个体性状（individual traits）仍未阐明。扩散能力（dispersal capability）是生活史的关键组分，其表达受限于能量产生的代谢能力（metabolic capacities）。学界关于代谢与生活史之间的矛盾关联，可通过纳入扩散能力与最大代谢率（maximal metabolic rates）的变异维度得到解释。

本研究以雌性翅多型（wing-polymorphic）沙地田野蟋蟀（Gryllus firmus）为实验材料，分别针对长翅（LW，具备飞行能力（flight-capability））与短翅（SW，早期终生繁殖力较高）进行选育，以此检验“对扩散能力的选择驱动代谢能力演化”这一假说（hypothesis）。实验结果显示，尽管静息代谢率（resting metabolic rates）无显著差异，但长翅蟋蟀的最大代谢率高于短翅蟋蟀，进而使其奔跑表现（running performance）更优。

本研究进一步通过比较驱动运动（locomotion）的组织的线粒体含量（mitochondrial content），并评估从长、短翅蟋蟀体内分离的线粒体的功能，阐明了生活史与新陈代谢协变的潜在机制。结果表明，长翅蟋蟀更高的代谢能力，得益于背腹飞行肌（dorsoventral flight muscle）的线粒体含量提升，以及负责燃料储存（fuel storage）与动员（mobilization）的脂肪体（fat body）内线粒体的生物能能力（bioenergetic capacities）增强。综上，针对飞行能力的选择会以性状和组织特异性的方式重塑代谢模式，从而扩大扩散过程所需的代谢能力。