Field data do not support a textbook example of convergent character displacement

Experimental evidence supporting convergent character displacement is rare; only one example exists and it is in the form of orientation and territory competition experiments performed in the laboratory. However, outcomes of laboratory experiments involving behaviour or competition can be artefacts of unnatural conditions and, therefore, the results of the previous experim ents supporting convergent character displacement are equivocal. In this st udy, we re-examine the evolution of melanic nuptial coloration in male thre e-spined stickleback (Gasterosteus aculeatus) inhabiting the Chehalis River drainage in Washington State. This novel nuptial coloration has been thoug ht to have evolved in response to competition for nesting territories with the co-distributed Olympic mudminnow (Novumbra hubbsi), which is also melan ic and breeds at the same time. I found that melanic stickleback males did not have an advantage over their red counterparts from typical populations when competing for nesting territories with Olympic mudminnows. Additionall y, competitive interactions between sticklebacks and mudminnows were rare i n both cage experiments and naturally breeding sticklebacks. Finally, melan ic coloration in the Chehalis populations did not develop until males were parental, well after the hypothesized territory establishment period. These results refute the only experimental support for convergent character disp lacement and emphasize the importance of conducting behavioural experiments and observations under natural conditions.