Amézquita Adolfo, Hödl Walter, Lima Albertina Pimentel, Castellanos Lina, Erdtmann Luciana, de Araújo Maria Carmozina
Department of Biological Sciences, University of Los Andes, AA 4976 Bogotá, Colombia.
Evolution. 2006 Sep;60(9):1874-87.
The efficacy of communication relies on detection of species-specific signals against the background noise. Features affecting signal detection are thus expected to evolve under selective pressures represented by masking noise. Spectral partitioning between the auditory signals of co-occurring species has been interpreted as the outcome of the selective effects of masking interference. However, masking interference depends not only on signal's frequency but on receiver's range of frequency sensitivity; moreover, selection on signal frequency can be confounded by selection on body size, because these traits are often correlated. To know whether geographic variation in communication traits agrees with predictions about masking interference effects, we tested the hypothesis that variation in the male-male communication system of the Amazonian frog, Allobates femoralis, is correlated with the occurrence of a single species calling within an overlapping frequency range, Epipedobates trivittatus. We studied frogs at eight sites, four where both species co-occur and four where A. femoralis occurs but E. trivittatus does not. To study the sender component of the communication system of A. femoralis and to describe the use of the spectral range, we analyzed the signal's spectral features of all coactive species at each site. To study the receiver component, we derived frequency-response curves from playback experiments conducted on territorial males of A. femoralis under natural conditions. Most geographic variation in studied traits was correlated with either call frequency or with response frequency range. The occurrence of E. trivittatus significantly predicted narrower and asymmetric frequency-response curves in A. femoralis, without concomitant differences in the call or in body size. The number of acoustically coactive species did not significantly predict variation in any of the studied traits. Our results strongly support that the receiver but not the sender component of the communication system changed due to masking interference by a single species.
通讯的功效依赖于在背景噪音中检测物种特异性信号。因此，影响信号检测的特征预计会在由掩蔽噪声所代表的选择压力下进化。同时出现的物种的听觉信号之间的频谱划分被解释为掩蔽干扰的选择效应的结果。然而，掩蔽干扰不仅取决于信号的频率，还取决于接收器的频率敏感范围；此外，对信号频率的选择可能会因对体型的选择而混淆，因为这些特征通常是相关的。为了了解通讯特征的地理变异是否与关于掩蔽干扰效应的预测一致，我们测试了这样一个假设：亚马逊蛙Allobates femoralis的雄蛙通讯系统的变异与在重叠频率范围内鸣叫的单个物种三带箭毒蛙（Epipedobates trivittatus）的出现有关。我们在八个地点研究了青蛙，四个地点两种物种同时出现，四个地点只有Allobates femoralis出现而三带箭毒蛙不出现。为了研究Allobates femoralis通讯系统的发送者部分并描述频谱范围的使用情况，我们分析了每个地点所有同时活跃的物种的信号频谱特征。为了研究接收器部分，我们从在自然条件下对Allobates femoralis领地雄蛙进行的回放实验中得出频率响应曲线。所研究特征的大多数地理变异与鸣叫频率或响应频率范围相关。三带箭毒蛙的出现显著预测了Allobates femoralis中更窄且不对称的频率响应曲线，而鸣叫或体型没有相应差异。声学上同时活跃的物种数量并未显著预测任何所研究特征的变异。我们的结果有力地支持了通讯系统的接收器部分而非发送者部分因单一物种的掩蔽干扰而发生了变化。
