Evolutionary loss of complexity in animal signals: cause and consequence

We identified hypotheses for the cause and consequences of the loss of complexity in animal signals and tested these using a genus of visually communicating lizards, the South-east Asian Draco lizards. Males of some species have lost the headbob component from their display, which is otherwise central to the communication of this genus. These males instead display a large, colourful dewlap to defend territories and attract mates. This dewlap initially evolved to augment the headbob component of the display, but has become the exclusive system of communication. We tested whether the loss of headbobs was caused by relaxed selection, habitat-dependent constraints, or size-specific energetic constraints on display movement. We then examined whether the consequences of this loss have been mitigated by increased signalling effort or complexity in the colour of the dewlap. It appears the increased cost of display movement resulting from the evolution of large body size might have contributed t..., Please see original manuscript for full details on data collection and processing., The data files are .csv files that can be opened using any text, spreadsheet or statistical program

本研究针对动物信号复杂性丧失的成因与后果提出假设，并以一类以视觉信号进行通讯的蜥蜴属——飞蜥属（Draco）蜥蜴为实验对象对上述假设进行验证。部分物种的雄性个体已在其展示行为中移除了点头动作（headbob）模块，而该模块原本是该属蜥蜴通讯行为的核心组成部分。取而代之的是，这些雄性会展示宽大且色彩艳丽的喉扇（dewlap）以捍卫领地、吸引配偶。该喉扇最初演化而来是为了强化展示行为中的点头动作模块，如今却已成为该属蜥蜴唯一的通讯系统。本研究验证了点头动作的丧失是否由选择压力松弛、生境依赖性约束，或是体型相关的展示运动能量约束所导致。随后，本研究进一步考察了这类丧失所带来的后果，是否可通过提升信号投入强度或喉扇色彩的复杂性得到缓解。现有结果显示，因体型演化增大所引发的展示运动成本上升，可能是促成点头动作丧失的诱因之一……完整的数据采集与处理细节请参见原始手稿。本研究所用数据文件均为.csv格式，可通过任意文本编辑器、电子表格软件或统计分析程序打开。