Data from: Dissolved organic carbon and unimodal variation in sexual signal coloration in mosquitofish: a role for light limitation?

Natural selection plays an important role in the evolution of sexual communication systems. Here, we assess the effect of two well-known selection agents, transmission environment and predation, on interpopulation variation in sexual signals. Our model system is a series of 21 populations of Bahamian mosquitofish subjected to independent variation in optical conditions and predation risk. We show that optically diverse environments, caused by locally variable dissolved organic carbon concentrations, rather than spatial variation in predation, drove divergence in fin coloration (fin redness). We found a unimodal pattern of phenotypic variation along the optical gradient indicating a threshold-type response of visual signals to broad variation in optical conditions. We discuss evolutionary and ecological mechanisms that may drive such a pattern as well as the implications of non-monotonic clines for evolutionary differentiation.自然选择在性通讯系统的演化过程中发挥着关键作用。本研究针对两种经典的选择因子——传播环境与捕食压力——对性信号种群间变异的影响展开评估。本研究的模式系统为21个巴哈马食蚊鱼种群，这些种群分别在光环境与捕食风险上存在独立变异。研究结果表明，由局地溶解有机碳浓度差异导致的光环境异质性，而非捕食压力的空间变异，驱动了鳍色（鳍部红度）的分化。我们在光梯度上发现了表型变异的单峰模式，这表明视觉信号对光环境的大范围变化存在阈值型响应。本研究还探讨了可能驱动该模式的演化与生态机制，以及非单调渐变群对演化分化的潜在影响。