Data from: Geographic variation in advertisement calls of a Microhylid frog—testing the role of drift and ecology

Acoustic signals for mating are important traits that could drive population differentiation and speciation. Ecology may play a role in acoustic divergence through direct selection (e.g., local adaptation to abiotic environment), constraint of correlated traits (e.g., acoustic traits linked to another trait under selection), and/or interspecific competition (e.g., character displacement). However, genetic drift alone can also drive acoustic divergence. It is not always easy to differentiate the role of ecology versus drift in acoustic divergence. In this study, we tested the role of ecology and drift in shaping geographic variation in the advertisement calls of Microhyla fissipes. We examined three predictions based on ecological processes: (1) the correlation between temperature and call properties across M. fissipes populations; (2) the correlation between call properties and body size across M. fissipes populations; and (3) reproductive character displacement (RCD) in call properties between M. fissipes populations that are sympatric with and allopatric to a congener M. heymonsi. To test genetic drift, we examined correlations among call divergence, geographic distance, and genetic distance across M. fissipes populations. We recorded the advertisement calls from 11 populations of M. fissipes in Taiwan, five of which are sympatrically distributed with M. heymonsi. We found geographic variation in both temporal and spectral properties of the advertisement calls of M. fissipes. However, the call properties were not correlated with local temperature or the callers' body size. Furthermore, we did not detect RCD. By contrast, call divergence, geographic distance, and genetic distance between M. fissipes populations were all positively correlated. The comparisons between phenotypic Qst (Pst) and Fst values did not show significant differences, suggesting a role of drift. We concluded that genetic drift, rather than ecological processes, is the more likely driver for the geographic variation in the advertisement calls of M. fissipes.

交配相关声学信号是能够推动种群分化与物种形成的重要性状。生态过程可通过多种途径引发声学性状分化：一是直接选择作用（例如，对非生物环境的局部适应），二是相关性状的约束效应（例如，声学性状与另一受选择性状存在关联），三是/或种间竞争作用（例如，性状替换）。然而，仅靠遗传漂变同样能够驱动声学性状分化。区分生态过程与遗传漂变在声学性状分化中的作用往往并非易事。
本研究以粗皮姬蛙（Microhyla fissipes）为研究对象，检验了生态过程与遗传漂变对其求偶鸣叫地理变异的塑造作用。我们基于生态过程提出三项预测：（1）粗皮姬蛙种群间温度与鸣叫性状的相关性；（2）粗皮姬蛙种群间鸣叫性状与体型大小的相关性；（3）与同属物种海曼氏姬蛙（M. heymonsi）同域分布和异域分布的粗皮姬蛙种群之间，鸣叫性状存在的生殖性状替换（Reproductive Character Displacement, RCD）。为检验遗传漂变的作用，我们分析了粗皮姬蛙种群间鸣叫分化、地理距离与遗传距离之间的相关性。
我们在中国台湾地区的11个粗皮姬蛙种群中录制了其求偶鸣叫，其中5个种群与海曼氏姬蛙呈同域分布。研究发现，粗皮姬蛙求偶鸣叫的时域与频域性状均存在地理变异。然而，鸣叫性状与当地温度或鸣叫个体的体型大小并无显著相关性。此外，我们未检测到生殖性状替换现象。与之相反，粗皮姬蛙种群间的鸣叫分化、地理距离与遗传距离均呈显著正相关。表型Qst（Pst）与固定指数（Fst）的比较未发现显著差异，这表明遗传漂变发挥了作用。
综上，相较于生态过程，遗传漂变更可能是驱动粗皮姬蛙求偶鸣叫地理变异的主要因素。