Temperature effects on interspecific eavesdropping in the wild

Mating signals are targets of conspecific signal recognition and sexual selection, but are also subject to abiotic temperature effects and to biotic interspecific eavesdroppers. In crickets, the male calling song becomes faster at warmer temperatures, and female crickets’ recognition of male song tracks temperature in a coordinated manner, termed ‘temperature coupling’. But female crickets are not the only ecologically relevant listeners: some cricket species are parasitized by Ormia ochracea, a parasitoid fly which finds its cricket hosts by eavesdropping on male cricket song. How temperature affects parasitoid fly phonotaxis to song is largely unexplored, with only one previous study conducted under field conditions. Here we explore six possible patterns of thermal effects on fly responses to cricket song, including temperature coupling, using field playbacks of synthetic Gryllus lineaticeps songs designed to be species-typical at various temperatures. We find that temperature does affect fly response, but that the temperature deviation of songs from ambient does not impact numbers of flies caught. We extend this finding by comparing the temperatures of the air and ground to show that temperature coupling is unlikely to be effective given microhabitat variation and differential rates of cooling in the evening hours when flies are most active. Our results can be interpreted more broadly to suggest temperature effects on intraspecific communication systems may be more tightly coupled than are effects on interspecific eavesdropping, and variation in thermal microhabitats in the field make it difficult to translate laboratory physiological responses to natural selection in the wild.

Methods
Data collected from field playback of cricket song to parasitoid flies. Data include field sampling information as well as numbers of flies attracted per playback.

Processing is minimal; raw data are presented. Basic functions (Mean, SD, MIN, MAX) calculated in Excel. Histogram and scatterplot from R.

求偶信号既是同种信号识别与性选择的作用靶标，同时也会受到非生物温度因子以及异种生物窃听者的影响。在蟋蟀类群中，雄性的召唤鸣唱会随温度升高而节奏加快，雌性蟋蟀对雄性鸣唱的识别会以协同方式匹配温度变化，该现象被称为“温度耦合（temperature coupling）”。但雌性蟋蟀并非唯一具备生态相关性的听觉接收者：部分蟋蟀物种会被奥米亚寄生蝇（Ormia ochracea）寄生，这类寄生蝇通过窃听雄性蟋蟀的召唤鸣唱定位宿主。目前关于温度如何影响寄生蝇对鸣唱的趋音行为的研究仍较为匮乏，仅有一项在野外条件下开展的先期研究。

本研究采用合成的条纹蟋蟀（Gryllus lineaticeps）召唤鸣唱进行野外回放实验，该合成鸣唱被设计为在各温度下均契合该物种的典型鸣唱特征，以此探讨温度对寄生蝇响应蟋蟀鸣唱的六种潜在作用模式，其中亦包含温度耦合效应。本研究发现，温度确实会影响寄生蝇的响应，但鸣唱与环境温度的偏差并不会对捕获的寄生蝇数量产生影响。

我们通过比较空气与地表温度进一步拓展了这一发现，结果表明：考虑到微生境的温度异质性，以及寄生蝇活动最为活跃的傍晚时段的降温速率差异，温度耦合效应在野外环境中大概率无法生效。本研究结果可被更广泛地解读为：温度对种内通讯系统的影响可能比对异种窃听者的影响更为紧密，而野外热微生境的异质性使得将实验室中观测到的生理响应推演至野外自然选择过程变得极为困难。

方法
本研究数据采集自野外播放蟋蟀召唤鸣唱以吸引寄生蝇的实验。数据集包含野外采样信息，以及每次回放实验所吸引的寄生蝇数量。

数据处理流程极为精简，仅展示原始数据。基础统计量（均值、标准差、最小值、最大值）通过Excel软件计算所得，直方图与散点图则通过R语言绘制。