Reduced Mating Vigor in Selection Lines of the Butterfly Bicyclus anynana

Despite its acknowledged value for testing evolutionary theory, artificial selection is vulnerable to artifacts that are difficult to control. Here, we show that lines of the butterfly Bicyclus anynana, being artificially selected for differences in egg size, show considerably reduced mating vigor and male mating success than control lines, which is attributed to presumed differences in the levels of inbreeding. Besides selection line, neither forewing length, body dry mass or fat content of males had a detectable impact on male mating performance. Because artificial selection may (e.g. due to inbreeding) yield inadvertent effects even on traits that seem not to be related to the target trait, their results should be interpreted with caution.