Differential geographic patterns in song components of male Albert’s lyrebirds

Geographic variation in bird song has received much attention in evolutionary studies, yet few consider components within songs that may be subject to different constraints and follow different evolutionary trajectories. Here we quantify patterns of geographic variation in the socially-transmitted ‘whistle’ song of Albert’s lyrebirds (Menura alberti), an oscine passerine renowned for its remarkable vocal abilities. Albert’s lyrebirds are confined to narrow stretches of suitable habitat, allowing us to map likely paths of cultural transmission using a species distribution model and least cost paths. We use quantitative methods to break the songs into three components present in all study populations: the introductory elements, the song body, and the final element. We compare geographic separation between populations with variation in these components as well as the full song. All populations were distinguishable by song, and songs varied according to the geographic distance between populations. However, within songs, only the introductory elements and song body could be used to distinguish among populations. The song body and final element changed with distance, but the introductory elements varied independently of geographic separation. These differing geographic patterns of within-song variation are unexpected, given that the whistle song components are always produced in the same sequence and may be perceived as a temporally-discrete unit. Knowledge of such spatial patterns of within-song variation enables further work to determine possible selective pressures and constraints acting on each song component, and provides spatially-explicit targets for preserving cultural diversity. As such, our study highlights the importance for science and conservation management of investigating spatial patterns within seemingly discrete behavioural traits at multiple levels of organisation. Usage notes contained on DRYAD record鸟类鸣唱的地理变异在进化生物学研究中广受关注，但鲜有研究考量鸣唱内部可能受不同约束、遵循不同进化轨迹的组成模块。本研究对艾氏琴鸟（Menura alberti）——一种以卓越发声能力闻名的雀形目鸣禽——的社会性传播鸣哨（whistle）鸣唱的地理变异模式进行了量化分析。艾氏琴鸟仅栖息于狭窄的适宜生境带中，这使得我们可通过物种分布模型（species distribution model）与最小成本路径（least cost paths）绘制其文化传播的潜在路径。我们采用定量方法，将所有研究种群的鸣唱划分为三个共有的组成部分：引子段落、鸣唱主体与终末段落。我们比较了种群间地理间隔与各组成部分及完整鸣唱的变异程度。所有种群均可通过鸣唱加以区分，且鸣唱差异随种群间地理距离的增加而增大。然而，在鸣唱内部，仅引子段落与鸣唱主体可用于区分不同种群。鸣唱主体与终末段落的变异随地理距离发生变化，但引子段落的变异与地理间隔无关。鉴于鸣哨的各组成部分始终以固定顺序呈现，且可能被感知为一个时间上分立的整体单元，这些鸣唱内部变异的不同空间模式着实出人意料。了解鸣唱内部的此类空间变异模式，可为后续研究确定作用于各鸣唱组成部分的潜在选择压力与约束条件提供基础，同时为保护鸣唱文化多样性提供空间针对性的保护目标。综上，本研究强调了在多组织层级层面探究看似单一的行为性状内部空间模式的重要性，这对于科学研究与保护管理均具有关键意义。DRYAD数据库记录中包含本数据集的使用说明。