Lengagne Thierry, Gomez Doris, Josserand Rémy, Voituron Yann
Université de Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1, ENTPE, CNRS, 6 rue Raphaël Dubois, 69622, Villeurbanne, France.
UMR 7179 CNRS National Museum of Natural History, Brunoy, France.
PLoS One. 2015 May 13;10(5):e0123828. doi: 10.1371/journal.pone.0123828. eCollection 2015.
Recently developed acoustic technologies - like automatic recording units - allow the recording of long sequences in natural environments. These devices are used for biodiversity survey but they could also help researchers to estimate global signal variability at various (individual, population, species) scales. While sexually-selected signals are expected to show a low intra-individual variability at relatively short time scale, this variability has never been estimated so far. Yet, measuring signal variability in controlled conditions should prove useful to understand sexual selection processes and should help design acoustic sampling schedules and to analyse long call recordings. We here use the overall call production of 36 male treefrogs (Hyla arborea) during one night to evaluate within-individual variability in call dominant frequency and to test the efficiency of different sampling methods at capturing such variability. Our results confirm that using low number of calls underestimates call dominant frequency variation of about 35% in the tree frog and suggest that the assessment of this variability is better by using 2 or 3 short and well-distributed records than by using samples made of consecutive calls. Hence, 3 well-distributed 2-minutes records (beginning, middle and end of the calling period) are sufficient to capture on average all the nightly variability, whereas a sample of 10 000 consecutive calls captures only 86% of it. From a biological point of view, the call dominant frequency variability observed in H. arborea (116Hz on average but up to 470 Hz of variability during the course of the night for one male) challenge about its reliability in mate quality assessment. Automatic acoustic recording units will provide long call sequences in the near future and it will be then possible to confirm such results on large samples recorded in more complex field conditions.
最近开发的声学技术——如自动录音设备——能够在自然环境中记录长序列声音。这些设备用于生物多样性调查，但也可以帮助研究人员在不同（个体、种群、物种）尺度上估计全球信号变异性。虽然性选择信号预计在相对较短的时间尺度内个体内部变异性较低，但到目前为止从未对这种变异性进行过估计。然而，在受控条件下测量信号变异性对于理解性选择过程应该是有用的，并且应该有助于设计声学采样计划以及分析长时间的叫声记录。我们在此利用36只雄树蛙（无斑雨蛙）在一个晚上的整体叫声产生情况，来评估叫声主频的个体内部变异性，并测试不同采样方法捕捉这种变异性的效率。我们的结果证实，使用少量叫声会低估树蛙约35%的叫声主频变化，并且表明通过使用2或3个短且分布良好的记录来评估这种变异性，比使用连续叫声样本更好。因此，3个分布良好的2分钟记录（叫声期的开始、中间和结束）平均足以捕捉所有夜间变异性，而10000个连续叫声的样本只能捕捉到其中的86%。从生物学角度来看，在无斑雨蛙中观察到的叫声主频变异性（平均116Hz，但一只雄蛙在夜间过程中变异性高达470Hz）对其在配偶质量评估中的可靠性提出了挑战。自动声学记录设备将在不久的将来提供长时间的叫声序列，届时将有可能在更复杂的野外条件下记录的大样本上证实这些结果。
