Data from: The metabolic costs of sexual signalling in the chirping katydid Plangia graminea (Serville) (Orthoptera: Tettigoniidae) are context dependent: cumulative costs add up fast

Katydids produce acoustic signals via stridulation which they use to attract conspecific females for mating. However, direct estimates of the metabolic costs of calling to date have produced diverse cost estimates and are limited to only a handful of insect species. In this study, we therefore investigated the metabolic cost of calling in a unstudied sub-Saharan katydid, Plangia graminea. Using wild-caught animals, we measured katydid metabolic rate using standard flow-through respirometry while simultaneously recording the number of calls produced. Overall, the metabolic rate during calling in P. graminea males was 59 percent higher than the resting metabolic rate (0.443&[plusmn]0.056 vs. 0.279&[plusmn]0.028 CO2 ml.g.h) although highly variable among individuals. While individual call costs were relatively inexpensive (ranging from 0.02-5.4 percent increase in metabolic rate per call) the individuals with cheaper calls called more often and for longer than those with expensive calls resulting in the former group having significantly greater cumulative costs over a standard amount of time (9.5 h). The metabolic costs of calling are however context dependent since the amount of time spent calling greatly influenced these costs in our trials. A power law function described this relationship between cumulative cost and percentage increase per call (y=130.21x-1.068, R squared=0.858); where y=cumulative cost, and x=percentage increase per call. The choice of metric employed for estimating energy costs (i.e. how costs are expressed) also affects the outcome and any interpretation of costs of sexual signalling. For example, the absolute, relative and cumulative metabolic costs of calling yield strongly divergent estimates and any fitness implications depend on the organism's energy budget and the potential trade-offs in allocation of resources that are made as a direct consequence of increased calling effort.螽斯通过摩擦发声（stridulation）产生声学信号，用于吸引同种雌性完成交配。然而迄今为止，针对鸣叫代谢成本的直接估算结果存在较大差异，且仅局限于少数几种昆虫物种。因此本研究以一种尚未被研究过的撒哈拉以南地区螽斯——草叶平螽（Plangia graminea）为对象，探究其鸣叫的代谢成本。研究采用野外捕获的个体，通过标准流式呼吸测量法（flow-through respirometry）测定螽斯的代谢速率，同时同步记录其鸣叫次数。整体而言，草叶平螽雄性在鸣叫期间的代谢速率较静息代谢率高出59%（分别为0.443±0.056与0.279±0.028 毫升二氧化碳每克每小时），不过个体间差异显著。尽管单次鸣叫的代谢成本相对较低（每鸣叫一次的代谢速率增幅介于0.02%至5.4%之间），但单次成本较低的个体，其鸣叫频率更高、持续时间更长，因此在标准时长（9.5小时）内的累计代谢成本显著高于单次成本较高的个体。不过鸣叫的代谢成本存在情境依赖性，本试验中，鸣叫时长对成本具有显著影响。累计代谢成本与单次鸣叫代谢增幅之间的关系可通过幂函数拟合：y=130.21x^(-1.068)，决定系数R²=0.858，其中y为累计代谢成本，x为单次鸣叫的代谢增幅百分比。用于估算能量成本的指标选择（即成本的表达方式）同样会影响研究结果，以及对性信号成本的解读。例如，鸣叫的绝对、相对与累计代谢成本的估算结果差异显著，而其适合度相关的意义则取决于生物体的能量预算，以及因鸣叫投入增加而直接引发的资源分配潜在权衡。