Data from: Tadpole begging reveals high quality

Parents can benefit from allocating limited resources non-randomly among offspring, and offspring solicitation (i.e., begging) is often hypothesized to evolve because it contains information valuable to choosy parents. We tested the diagnostic predictions of three ‘honest begging’ hypotheses –Signal of Need, Signal of Quality, and Signal of Hunger – in the tadpoles of a terrestrial frog (Oophaga pumilio). In this frog, mothers provision tadpoles with trophic eggs, and when mothers visit, tadpoles perform a putative begging signal by stiffening their bodies and vibrating rapidly. We assessed the information content of intense tadpole begging with an experimental manipulation of tadpole condition (need/quality) and food-deprivation (hunger). This experiment revealed patterns consistent with the Signal of Quality hypothesis and directly counter to predictions of Signal of Need and Signal of Hunger. Begging effort and performance were higher in more developed and higher condition tadpoles and declined with food-deprivation. Free-living mothers were unlikely to feed tadpoles of a non-begging species experimentally cross-fostered with their own, and allocated larger meals to more developed tadpoles and those that vibrated at higher speed. Mother O. pumilio favour their high quality young, and because their concurrent offspring are reared in separate nurseries, must do so by making active allocation decisions. Our results suggest that these maternal choices are based at least in part on offspring signals, indicating that offspring solicitation can evolve to signal high quality.亲本若能在子代间非随机分配有限资源，便可从中获益；而子代恳求行为（即乞食行为）常被假设演化而来，原因在于其携带了对具有选择偏好的亲本而言极具价值的信息。我们针对陆生蛙类——草莓箭毒蛙（Oophaga pumilio）——的蝌蚪，检验了三项“诚实乞食假说”的诊断性预测：需求信号假说（Signal of Need）、质量信号假说（Signal of Quality）与饥饿信号假说（Signal of Hunger）。该蛙类的母蛙会向蝌蚪提供营养卵（trophic eggs）；当母蛙到访时，蝌蚪会通过身体僵硬并快速振动的方式展现出推定的乞食信号。我们通过操控蝌蚪的状态（需求/质量）与食物剥夺程度（饥饿水平），评估了高强度蝌蚪乞食行为的信息含量。本实验揭示的结果模式与质量信号假说相符，却与需求信号假说和饥饿信号假说的预测直接相悖。发育程度更高、状态更佳的蝌蚪，其乞食投入与表现均更强，且该乞食表现会随食物剥夺程度的加深而下降。野生母蛙不会为那些被实验性交叉抚育的、原本无乞食行为的蝌蚪投喂食物，且会向发育程度更高、振动速度更快的蝌蚪提供更多食物。草莓箭毒蛙的母蛙会青睐高质量的子代；由于其同期抚育的子代均在独立的保育环境中成长，母蛙必须通过主动的资源分配决策来实现这一选择。我们的研究结果表明，这些母性选择至少部分基于子代发出的信号，这也印证了子代恳求行为可演化出传递高质量信号的功能。