Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panamá.
Integr Comp Biol. 2021 Oct 4;61(3):887-899. doi: 10.1093/icb/icab138.
Researchers have long examined the structure of animal advertisement signals, but comparatively little is known about how often these signals are repeated and what factors predict variation in signaling rate across species. Here, we focus on acoustic advertisement signals to test the hypothesis that calling males experience a tradeoff between investment in the duration or complexity of individual calls and investment in signaling over long time periods. This hypothesis predicts that the number of signals that a male produces per 24 h will negatively correlate with (1) the duration of sound that is produced in each call (the sum of all pulses) and (2) the number of sound pulses per call. To test this hypothesis, we measured call parameters and the number of calls produced per 24 h in 16 species of sympatric phaneropterine katydids from the Panamanian rainforest. This assemblage also provided us with the opportunity to test a second taxonomically specific hypothesis about signaling rates in taxa such as phaneropterine katydids that transition from advertisement calls to mating duets to facilitate mate localization. To establish duets, male phaneropterine katydids call and females produce a short acoustic reply. These duets facilitate searching by males, females, or both sexes, depending on the species. We test the hypothesis that males invest either in calling or in searching for females. This hypothesis predicts a negative relationship between how often males signal over 24 h and how much males move across the landscape relative to females. For the first hypothesis, there was a strong negative relationship between the number of signals and the duration of sound that is produced in each signal, but we find no relationship between the number of signals produced per 24 h and the number of pulses per signal. This result suggests the presence of cross-taxa tradeoffs that limit signal production and duration, but not the structure of individual signals. These tradeoffs could be driven by energetic limitations, predation pressure, signal efficacy, or other signaling costs. For the second hypothesis, we find a negative relationship between the number of signals produced per day and proportion of the light trap catch that is male, likely reflecting males investing either in calling or in searching. These cross-taxa relationships point to the presence of pervasive trade-offs that fundamentally shape the spatial and temporal dynamics of communication.
研究人员长期以来一直在研究动物广告信号的结构，但对于这些信号的重复频率以及哪些因素会预测物种间信号传递率的变化知之甚少。在这里，我们专注于声学广告信号，以检验以下假设：发出叫声的雄性在个体叫声的持续时间或复杂性的投入与长时间信号传递的投入之间存在权衡。该假设预测，雄性在 24 小时内发出的信号数量将与以下因素呈负相关：（1）每次叫声中产生的声音持续时间（所有脉冲的总和）；（2）每次叫声中的脉冲数量。为了验证这一假设，我们在巴拿马雨林的 16 种同域 phaneropterine 蝉中测量了叫声参数和 24 小时内发出的叫声数量。这个集合还为我们提供了测试关于在 phaneropterine 蝉等分类群中信号传递率的第二个分类特异性假设的机会，这些蝉从广告叫声过渡到交配二重奏，以促进配偶定位。为了建立二重奏，雄性 phaneropterine 蝉发出叫声，而雌性则发出短暂的声音回应。这些二重奏有利于雄性、雌性或两性的搜索，具体取决于物种。我们测试了以下假设：雄性要么投资于鸣叫，要么投资于寻找雌性。该假设预测，雄性在 24 小时内信号传递的频率与雄性相对于雌性在景观中的移动量之间存在负相关关系。对于第一个假设，信号数量与每次信号产生的声音持续时间之间存在强烈的负相关关系，但我们发现 24 小时内发出的信号数量与每个信号的脉冲数量之间没有关系。该结果表明存在跨分类群的权衡，限制了信号的产生和持续时间，但不限制单个信号的结构。这些权衡可能由能量限制、捕食压力、信号功效或其他信号成本驱动。对于第二个假设，我们发现每天发出的信号数量与灯光陷阱捕获的雄性比例之间存在负相关关系，这可能反映出雄性要么投资于鸣叫，要么投资于搜索。这些跨分类群的关系表明存在普遍的权衡，这些权衡从根本上塑造了通信的空间和时间动态。
