Data from: Environmental conditions limit attractiveness of a complex sexual signal in the túngara frog

Animals choosing particular display sites often balance sexual and natural selection pressures. Here we assess how physical properties of display sites can alter this balance by influencing signal production and attractiveness of the túngara frog (Physalaemus pustulosus). Males that call from very shallow water bodies (few mm depth) benefit from reduced predation risk, but by manipulating water levels, we show that this comes at a cost of reduced attractiveness to females. Our data show that calling from shallower water reduces a male's ability to float, limits the inflation of his vocal sac, and consequently reduces signal conspicuousness in terms of amplitude and complexity. Our results demonstrate that display site properties can set limits on signal production and attractiveness and may hence influence signal evolution. Signallers may shift between sites or engineer their display location, which can play a crucial role in signal divergence and speciation, particularly in a rapidly changing world.

选择特定展示位点的动物，往往需要在性选择（sexual selection）与自然选择（natural selection）的双重压力下达成平衡。本研究以通加拉蛙（túngara frog，*Physalaemus pustulosus*）为研究对象，探究展示位点的物理特性如何通过影响信号产生与配偶吸引力，进而改变这一平衡关系。从极浅水体（深度仅数毫米）鸣叫的雄性个体，可获得被捕食风险降低的益处，但本研究通过操控水位发现，该益处是以降低对雌性的吸引力为代价的。实验数据显示，在更浅的水域鸣叫会削弱雄性的漂浮能力，限制其声囊（vocal sac）的充气膨胀，进而降低信号在振幅（amplitude）与复杂度（complexity）层面的信号醒目度（signal conspicuousness）。本研究结果证实，展示位点的物理特性会对信号产生与配偶吸引力形成限制，从而可能影响信号的演化进程。信号发送者可在不同位点间切换，或是主动改造自身的展示位置，这一过程对信号分化（signal divergence）与物种形成（speciation）至关重要，在当今快速变化的全球环境中尤为如此。