Data from: Phenotypic integration and the evolution of signal repertoires: a case study of treefrog acoustic communication

Animal signals are inherently complex phenotypes with many interacting parts combining to elicit responses from receivers. The pattern of interrelationships between signal components reflects the extent to which each component is expressed, and responds to selection, either in concert with or independently of others. Furthermore, many species have complex repertoires consisting of multiple signal types used in different contexts, and common morphological and physiological constraints may result in interrelationships extending across the multiple signals in species’ repertoires. The evolutionary significance of interrelationships between signal traits can be explored within the framework of phenotypic integration, which offers a suite of quantitative techniques to characterize complex phenotypes. In particular, these techniques allow for the assessment of modularity and integration, which describe, respectively, the extent to which sets of traits covary either independently or jointly. Although signal and repertoire complexity are thought to be major drivers of diversification and social evolution, few studies have explicitly measured the phenotypic integration of signals to investigate the evolution of diverse communication systems. We applied methods from phenotypic integration studies to quantify integration in the two primary vocalization types (advertisement and aggressive calls) in the treefrogs Hyla versicolor, Hyla cinerea, and Dendropsophus ebraccatus. We recorded male calls and calculated standardized phenotypic variance–covariance (P) matrices for characteristics within and across call types. We found significant integration across call types, but the strength of integration varied by species and corresponded with the acoustic similarity of the call types within each species. H. versicolor had the most modular advertisement and aggressive calls and the least acoustically similar call types. Additionally, P was robust to changing social competition levels in H. versicolor. Our findings suggest new directions in animal communication research in which the complex relationships among the traits of multiple signals are a key consideration for understanding signal evolution.

动物信号本质上属于一类复杂表型，由诸多相互作用的组分共同构成，以触发接收者的行为响应。信号组分间的关联模式，可反映各组分的表达水平，及其独立或与其他组分协同应对选择压力的程度。此外，诸多物种拥有复杂的信号库，包含多种用于不同情境的信号类型；而常见的形态与生理约束，可能会跨物种信号库中的多种信号形成关联。信号性状间关联的进化意义，可在表型整合（phenotypic integration）的框架下展开探究——该框架提供了一系列定量技术，用于表征复杂表型。其中尤为关键的是，这些技术可用于评估模块化与整合性：二者分别描述了性状集独立协变或联合协变的程度。尽管学界普遍认为，信号与信号库复杂度是物种分化与社会进化的核心驱动因素，但鲜有研究通过直接测量信号的表型整合，来探究多样化通讯系统的演化。我们将表型整合研究的方法应用于量化3种树蛙（Hyla versicolor、Hyla cinerea与Dendropsophus ebraccatus）的两种主要鸣叫类型——求偶鸣叫与攻击鸣叫——的整合程度。我们录制了雄性个体的鸣叫，并计算了鸣叫类型内部及跨鸣叫类型的性状的标准化表型方差-协方差（P）矩阵。研究发现，不同鸣叫类型间存在显著的整合性，但整合强度因物种而异，且与各物种内部两种鸣叫类型的声学相似度相匹配。其中，Hyla versicolor的求偶鸣叫与攻击鸣叫模块化程度最高，二者的声学相似度也最低。此外，在Hyla versicolor中，表型P矩阵对社会竞争水平的变化具有鲁棒性。我们的研究结果为动物通讯研究指明了新方向：在理解信号演化的过程中，需将多信号性状间的复杂关联作为核心考量因素。