Communication and Social Behaviour Group, Max Planck Institute for Ornithology, Seewiesen, Germany.
Biol Lett. 2012 Dec 23;8(6):913-6. doi: 10.1098/rsbl.2012.0676. Epub 2012 Sep 12.
Signal plasticity is considered an important step in the evolution of animal communication. In acoustic communication, signal transmission is often constrained by background noise. One adaptation to evade acoustic signal masking is the Lombard effect, in which an animal increases its vocal amplitude in response to an increase in background noise. This form of signal plasticity has been found in mammals, including humans, and some birds, but not frogs. However, the evolution of the Lombard effect is still unclear. Here we demonstrate for the first time the Lombard effect in a phylogentically basal bird species, the tinamou Eudromia elegans. By doing so, we take a step towards reconstructing the evolutionary history of noise-dependent vocal plasticity in birds. Similar to humans, the tinamous also raised their vocal pitch in noise, irrespective of any release from signal masking. The occurrence of the Lombard effect in a basal bird group suggests that this form of vocal plasticity was present in the common ancestor of all living birds and thus evolved at least as early as 119 Ma.
信号可塑性被认为是动物通讯进化的重要步骤。在声学通讯中，信号传输常常受到背景噪声的限制。一种逃避声信号掩蔽的适应机制是 Lombard 效应，即动物会根据背景噪声的增加而增加其声音幅度。这种形式的信号可塑性已在哺乳动物（包括人类）和一些鸟类中发现，但在青蛙中尚未发现。然而，Lombard 效应的进化仍不清楚。在这里，我们首次在一个系统发育上基础的鸟类物种——蓝胸鹑 Eudromia elegans 中证明了 Lombard 效应。通过这样做，我们朝着重建鸟类中依赖噪声的发声可塑性的进化历史迈出了一步。与人类相似，蓝胸鹑在噪声中也提高了它们的发声频率，而不受信号掩蔽的影响。这种 Lombard 效应在一个基础鸟类群体中的出现表明，这种形式的发声可塑性存在于所有现存鸟类的共同祖先中，因此至少在 1.19 亿年前就已经进化了。
