Data from: Evolution of Acoustic and Visual Signals in Asian Barbets

The study of animal communication systems is an important step towards gaining greater understanding of the processes influencing diversification because signals often play an important role in mate choice and can lead to reproductive isolation. Signal evolution can be influenced by a diversity of factors such as biophysical constraints on the emitter, the signalling environment, or selection to avoid heterospecific matings. Furthermore, because signals can be costly to produce, trade-offs may exist between different types of signals. Here, we apply phylogenetic comparative analyses to study the evolution of acoustic and visual signals in Asian barbets, a clade of non-Passerine, forest-dependent birds. Our results suggest that evolution of acoustic and visual signals in barbets is influenced by diverse factors, such as morphology and signalling environment, suggesting a potential effect of sensory drive. We found no trade-offs between visual and acoustic signals. Quite to the contrary, more colourful species sing significantly longer songs. Song characteristics presented distinct patterns of evolution. Song frequency diverged early on and the rate of evolution of this trait appears to be constrained by body size. On the other hand, characteristics associated with length of the song presented evidence for more recent divergence. Finally, our results indicate that there is a spatial component to the evolution of visual signals, and that visual signals are more divergent between closely related taxa than acoustic signals. Hence, visual signals in these species could play a role in speciation or reinforcement of reproductive isolation following secondary contacts.

对动物通讯系统的研究，是增进我们对驱动物种分化的各类过程的认知的重要一步，因为信号往往在配偶选择中发挥关键作用，并可引发生殖隔离。信号演化可受到多种因素的影响，例如信号发送者所受的生物物理约束、信号传递环境，或是为避免异种交配而产生的选择压力。此外，由于信号的产生需付出成本，不同类型的信号之间可能存在演化权衡。在此研究中，我们运用系统发育比较分析（phylogenetic comparative analyses）方法，对亚洲拟鴷类群——一类非雀形目、依赖森林栖息的鸟类——的声学与视觉信号演化展开研究。我们的研究结果表明，这类拟鴷的声学与视觉信号演化受到形态特征、信号传递环境等多种因素的影响，这暗示感官驱动（sensory drive）可能在其中发挥了潜在作用。我们未发现视觉与声学信号之间存在演化权衡，恰恰相反，体色更为艳丽的物种，其鸣唱时长显著更长。鸣唱特征呈现出差异化的演化模式：鸣唱频率较早发生分化，且该性状的演化速率似乎受到体型大小的约束；而与鸣唱时长相关的特征，则展现出较晚近的分化迹象。此外，我们的研究结果显示，视觉信号的演化存在空间维度特征，且亲缘关系较近的类群之间，视觉信号的分化程度要高于声学信号。因此，这类物种的视觉信号，可能在物种形成或是次生接触后的生殖隔离强化过程中发挥作用。