Evolution of Sexual Signals: Within and between Species Variation in a Dual Function Sex-Pheromone Component in Two Noctuid Moths

Sexual signals are key components in mate attraction and mate choice. Sexual attraction through sex pheromones is best studied in moths, where females emit species-specific pheromone blends. This species-specificity stems from the presence/absence and ratios of the different components. For example, the two closely related noctuid moth species Heliothis subflexa and Heliothis virescens produce similar sex pheromone blends, with one major difference: acetate esters (hereafter referred to as “acetates”). Only H. subflexa females produce acetate in their sex pheromone blend which play a dual function: attracting conspecific males, while repelling the sympatrically occurring species, H. virescens. Moreover, H. subflexa females produce high acetate levels when H. virescens are present, but low in their absence.

In this thesis I investigated both within and between species variation in acetate levels, by studying the genetic architecture responsible for this variation and looking at the potential costs associated with high acetate levels. We identified a few candidate genes that are involved in acetates variation in two previously found QTLs. In addition, we selected for high and low levels of acetate in H. subflexa and investigated how this affected the pheromone blend. Finally, we investigated whether the production of high acetate levels comes with a cost, by rearing the two selection lines under food stress conditions. Our results indicate that 1) intra- and inter-specific variation in acetate levels can be explained by a combination of shared and unique genetic factors and 2) high levels of acetate come with a fitness cost under stressful conditions.

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