Data from: The cost of sexual signaling in yeast

The handicap principle holds that costly sexual signals can reliably indicate mate quality. Only individuals of high quality can afford a strong signal - the cost of signaling is relatively lower for high quality signalers than for low quality signalers. This critical property is difficult to test experimentally because the benefit of signaling on mating success, and cost of signaling on other components of fitness, cannot easily be separated in obligate sexual organisms. We therefore studied the facultatively sexual yeast Saccharomyces cerevisiae, which produces pheromones to attract potential mates. To precisely measure the cost of signaling, the signal was reduced or removed by deleting one or both copies of the pheromone-encoding genes and measuring asexual growth rate in competition with a wild-type signaler. We manipulated signaler quality either by changing the quality of the assay environment or by changing the number of deleterious mutations carried. For both types of treatment, we found that the cost of signaling decreased as the quality of the signaler increased, demonstrating that the yeast pheromone signal has the key property required for selection under the handicap principle. We found that cells of high genetic quality produce stronger signals than low quality cells, verifying that the signal is indeed honest.累赘原理（handicap principle）指出，代价高昂的性信号能够可靠地反映配偶质量。仅高质量个体能够负担得起强信号的成本——相较于低质量信号发送者，高质量信号发送者的信号成本相对更低。这一关键特性难以通过实验验证，因为在专性有性生物中，信号发送对交配成功率的益处，与信号发送对适合度其他组分的成本，难以被独立分离。为此，我们以兼性有性生物酿酒酵母（Saccharomyces cerevisiae）为研究对象，该生物通过分泌信息素吸引潜在配偶。为精准测量信号发送成本，我们通过敲除信息素编码基因的单拷贝或双拷贝来削弱或移除信号，并通过与野生型信号发送者的竞争实验测定其无性生长速率。我们通过两种方式调控信号发送者的质量：一是改变实验环境的质量，二是调整其携带的有害突变数量。在两种处理方式下，我们均发现信号发送成本随信号发送者质量的提升而降低，这证明酿酒酵母的信息素信号具备累赘原理下选择所需的关键特性。我们还发现，遗传质量较高的细胞所产生的信号强于低质量细胞，验证了该信号确实为诚实信号。