Data from: Sensory drive does not explain reproductive character displacement of male acoustic signals in the Upland Chorus Frog (Pseudacris feriarum)

Biotic and abiotic factors have been proposed to explain patterns of reproductive character displacement, but which factor is most important to character displacement of acoustic signals is not clear. Male vocalizations of the frog Pseudacris feriarum are known to undergo reproductive character displacement in areas of sympatry with P. brimleyi and P. nigrita. Despite evidence for reinforcement as an important mechanism, local adaptation via sensory drive might explain this pattern because Pseudacris breed in different habitat types and mating signals are exposed to a variety of environments. We tested the sensory drive hypothesis by playing synthesized vocalizations representing the spectrum of variation in P. feriarum at 12 different study sites. If sensory drive has occurred, then vocalizations should transmit better in the site of origin or at ecologically similar sites. We found that variation in acoustic signals did not produce better transmission in particular sites, the effect of site was uniform, and acoustic signals often transmitted better in habitats external to their origin. Ecological variation among habitats did not explain signal degradation. Our playback experiments, ecological analyses, and comparisons of different habitat types provide no support for sensory drive as a process promoting reproductive character displacement in this system. Reinforcement is the more likely primary mechanism.已有研究提出用生物因子与非生物因子来解释生殖性状置换（reproductive character displacement）的分布模式，但目前尚不清楚在声学信号的性状置换中，何种因子发挥着最为关键的作用。已知饰纹拟蝗蛙（Pseudacris feriarum）的雄性鸣唱信号，在与布莱利拟蝗蛙（P. brimleyi）和黑带拟蝗蛙（P. nigrita）同域分布的区域中，会发生生殖性状置换现象。尽管已有证据表明强化选择（reinforcement）是该现象的重要作用机制，但通过感觉驱动（sensory drive）实现的局部适应或许也能解释这一模式——因为拟蝗蛙属（Pseudacris）物种的繁殖生境类型各异，且交配信号会暴露于多样的环境之中。本研究通过在12个不同研究点位播放涵盖饰纹拟蝗蛙鸣唱信号变异谱系的合成鸣唱，对感觉驱动假说进行了检验。若感觉驱动机制确实存在，则鸣唱信号在其起源生境或生态相似的生境中传播效果应更佳。本研究结果显示，声学信号的变异并未使特定点位的传播效果得到提升，不同点位的传播效应并无显著差异，且鸣唱信号往往在其起源生境之外的生境中传播效果更佳。生境间的生态差异也无法解释信号衰减现象。本研究的回放实验、生态分析以及不同生境类型的对比结果，均不支持感觉驱动作为促进该类群生殖性状置换的作用机制。强化选择更有可能是该现象的主要作用机制。