Experimental Evolution of a Pheromone Signal

Abstract

ABSTRACTSexual signals are important in speciation, but understanding their evolution is complex as these signals are often composed of multiple, genetically interdependent components. To understand how signals evolve, we thus need to consider selection responses in multiple components and account for the genetic correlations among components. One intriguing possibility is that selection changes genetic correlations between components under selection and those not under selection, reducing evolutionary constraints. However, this hypothesis remains largely untested empirically. In this study, we investigate the evolutionary response of the multi-component female sex pheromone blend of the moth Heliothis subflexa to 10 generations of artificial selection. We observed a selection response of about 3/4s of a phenotypic standard deviation in the components under selection. Interestingly, other pheromone components that are biochemically and genetically linked to the components under selection did not change. We found that this component-specific selection response was likely facilitated due to reduced genetic coupling between the component under selection and the components not under selection, resulting from changes in genetic covariances within the 10 generations of selection. Our findings provide rare empirical support for an intriguing mechanism by which a sexual signal can respond to selection without possible constraints from indirect selection responses.SUMMARY STATEMENTThis study reveals a mechanism that can facilitate evolution of sex pheromone components under selection independent of other components of the sex pheromone that are not under selection.