Data from: Uneven sampling and the analysis of vocal performance constraints

Studies of trilled vocalizations provide a premiere illustration of how performance constraints shape the evolution of mating displays. In trill production, vocal tract mechanics impose a trade-off between syllable repetition rate and frequency bandwidth, with the trade-off most pronounced at higher values of both parameters. Available evidence suggests that trills that simultaneously maximize both traits are more threatening to males or more attractive to females, consistent with a history of sexual selection favoring high-performance trills. Here, we identify a sampling limitation that confounds the detection and description of performance trade-offs. We reassess 70 data sets (from 26 published studies) and show that sampling limitations afflict 63 of these to some degree. Traditional upper-bound regression, which does not control for sampling limitations, detects performance trade-offs in 33 data sets; yet when sampling limitations are controlled, performance trade-offs are detected in only 15. Sampling limitations therefore confound more than half of all performance trade-offs reported using the traditional method. An alternative method that circumvents this sampling limitation, which we explore here, is quantile regression. Our goal is not to question the presence of mechanical trade-offs on trill production but rather to reconsider how these trade-offs can be detected and characterized from acoustic data.

对颤鸣发声（trilled vocalizations）的研究，堪称阐释性能约束如何塑造求偶展示演化的经典范例。在颤鸣的产生过程中，声道力学机制会在音节重复速率与频率带宽之间形成权衡关系，且当两项参数均处于较高水平时，该权衡效应最为显著。现有证据表明，能同时最大化这两项特征的颤鸣，对雄性竞争者更具威慑力，或对雌性更具吸引力，这与青睐高性能颤鸣的性选择演化历史相符。本研究指出了一类会干扰性能权衡检测与描述的采样局限性问题。我们重新评估了来自26项已发表研究的70组数据集，结果显示其中63组数据集均存在不同程度的采样局限性。传统的上限回归（upper-bound regression）方法未对采样局限性进行控制，可在33组数据集中检测到性能权衡效应；但在对采样局限性加以控制后，仅能在15组数据集中检测到性能权衡。因此，采用传统方法报告的性能权衡结果中，超过半数均受到采样局限性的干扰。本研究还探讨了一种可规避该采样局限性的替代方法——分位数回归（quantile regression）。我们的研究目的并非质疑颤鸣产生过程中存在机械权衡，而是重新思考如何从声学数据中检测并刻画这类权衡关系。