Data from: Multivariate phenotypic selection on a complex sexual signal

Animal signals are complex, comprising multiple components that receivers may use to inform their decisions. Components may carry information of differing value to receivers, and selection on one component could modulate or reverse selection on another, necessitating a multivariate approach to estimating selection gradients. However, surprisingly few empirical studies have estimated the strength of phenotypic selection on complex signals with appropriate design and adequate power to detect non-linear selection. We used phonotaxis assays to measure sexual selection on the advertisement signal of Cope's gray tree frog, Hyla chrysoscelis. Female preferences were assessed for five signal components using single-stimulus and two-stimulus behavioral assays. Linear, quadratic, and correlational selection gradients were estimated from the single-stimulus data. Significant directional selection is acting on call duration, call rate, pulse rate, and relative amplitude; stabilizing selection is acting on call duration and call rate. Under the two-stimulus paradigm, conclusions were qualitatively different, revealing non-linear selection on all components except call duration. For individual subjects, the outcomes of single-stimulus and two-stimulus trials were frequently discordant, suggesting that the choice of testing paradigm may affect conclusions drawn from experiments.

动物信号复杂多样，由多个可被接收者用于辅助决策的组分构成。不同组分对接收者的信息价值存在差异，对某一组分的选择作用可能会调控甚至逆转针对另一组分的选择作用，因此需要采用多变量方法来估算选择梯度。然而，令人意外的是，极少有实证研究采用恰当的实验设计与足够的统计效力，来估算复杂信号所受表型选择的强度并检测非线性选择作用。本研究采用趋声性实验（phonotaxis assays），针对科普氏灰树蛙（Cope's gray tree frog, *Hyla chrysoscelis*）的广告鸣唱信号开展性选择（sexual selection）量化分析。我们通过单刺激与双刺激行为实验，针对5种信号组分评估了雌性配偶偏好。基于单刺激实验数据，我们估算得到线性、二次及相关选择梯度。结果显示，鸣声时长、鸣声速率、脉冲速率与相对振幅受到显著的定向选择；而鸣声时长与鸣声速率则受到稳定选择（stabilizing selection）。在双刺激范式（two-stimulus paradigm）下，实验结论则存在质性差异：除鸣声时长外，其余所有信号组分均受到非线性选择作用。针对单个实验个体的分析显示，单刺激与双刺激实验的结果往往不一致，这表明实验范式的选择可能会影响实验推导得出的研究结论。