Data from: The theory of island biogeography and soundscapes: species diversity and the organization of acoustic communities

Aim: On islands, species richness is reduced and interspecific competition relaxed in relation to the mainland, allowing species to use broader ecological niches. These factors are known to affect diet and morphology, but can also affect communication and acoustic signaling in particular. However, no study has ever compared insular and continental soundscapes to determine to which extent islands present reduced acoustic richness (number of co-vocalizing species) and fewer constraints for vocalizing species. Location: São Tomé Island, Mount Cameroon, Madeira Island, Southern France Taxon: Birds Methods: We compared two pairs of insular and continental soundscapes: one in a temperate zone, the other in the tropics. We recorded sounds produced in similar types of primary forests and measured acoustic richness and ambient noise profiles. We then assessed acoustic niche organization by computing, for each community, species turnover, temporal and frequency overlaps, and acoustic avoidance. Results: We found fewer species co-vocalizing on islands compared to mainland and in temperate compared to tropical region. Ambient noise was louder in the tropics and occupied a wider frequency range, especially on the mainland, thereby revealing a reduction in available acoustic space for tropical mainland birds. In this more crowded and noisy soundscape, species presented a higher acoustic turnover, overlapped less in time and in frequency with each other and acoustically avoided each other more when compared to the three other communities. Main conclusions: Soundscapes differed and imposed fewer constraints on vocalizing species along the species diversity gradient from tropical mainland to temperate island. Acoustic niche partitioning increased with species richness and was associated with increased levels of acoustic interference. Results set a scene for an effect of relaxed competition on song evolution on islands, especially in the tropics.

研究目的：相较于大陆生境，岛屿的物种丰富度更低，种间竞争更为缓和，使得物种能够利用更宽泛的生态位。已知此类因素会影响物种的食性与形态，同时也会尤其对通讯行为及声学信号产生影响。然而目前尚无研究对比岛屿与大陆的声景（soundscape），以明确岛屿在多大程度上降低了声学丰富度（acoustic richness，即共鸣物种（co-vocalizing species）的数量），并为鸣唱物种带来更少的约束。
研究地点：圣多美岛、喀麦隆山、马德拉岛、法国南部。
研究类群：鸟类。
研究方法：本研究对比了两组岛屿-大陆声景配对：一组位于温带区域，另一组位于热带区域。我们在相似类型的原生林内录制声音，并测量声学丰富度与环境噪声谱特征。随后，通过计算每个群落的物种更替率、时间与频率重叠度以及声学避让（acoustic avoidance）行为，我们评估了声学生态位（acoustic niche）的组织模式。
研究结果：我们发现，相较于大陆生境，岛屿上的共鸣物种数量更少；相较于热带区域，温带生境的共鸣物种数量同样更少。热带区域的环境噪声更强，且占据更宽的频率范围，尤其在大陆生境中如此，这表明热带大陆鸟类可利用的声学空间有所缩减。相较于其余三个群落，在这一更拥挤且嘈杂的声景中，物种间的声学更替率更高，时间与频率重叠度更低，且彼此间的声学避让行为更为显著。
主要结论：声景存在显著差异，且沿从热带大陆到温带岛屿的物种多样性梯度，对鸣唱物种施加的约束逐渐减少。声学生态位分化（acoustic niche partitioning）随物种丰富度提升而增强，且与声学干扰水平升高密切相关。本研究结果为探讨岛屿（尤其热带岛屿）上种间竞争缓和对鸣唱演化的影响提供了研究基础。