Evidence of female preference for hidden sex signals in distant fish species

Strong selection against heterospecific sex signals, which includes both receivers and signallers, is considered to be the most significant causal factor in animal signal modification and is expected to prevent mate misinterpretation. Using a simultaneous choice bioassay, we tested the continued use of primordial sex signals in distantly related and geographically separated fish species, Pseudorasbora parva and Pimephales promelas. Here, we show that intraspecific selection pressures have not caused significant sex chemical signal differentiation between the 2 species and that mate attraction is likely due to a combination of common ancestry and an absence of divergence in allopatry. In the absence of mate discrimination among species, which have evolved for long periods of time in allopatry, reunification through species translocation could represent an overlooked risk of pheromone pollution.