Sexual selection in a dynamic world The causes and consequences of variation in sexual signals and responses

Sexual selection is a powerful evolutionary force that can lead to divergence in mating signals and preferences. In many moth species, females emit a sex pheromone to attract males. Changes in female pheromone signals and male responses promote the evolution of sexual communication systems. Therefore, it is important to understand the causes and consequences of variation in signals and responses, especially in this era of a rapidly changing world. In this thesis, I gave a general introduction to the topics and the study systems (CHAPTER 1). I assessed what determines the strength of sexual selection in the polygamous moth Heliothis virescens (CHAPTER 2). Furthermore, I assessed the level and extent of geographic variation in the sexual communication of the moth Helicoverpa armigera (CHAPTER 3). Since parasites can have major effects on sexual attraction in their hosts, I further investigated the presence of a Ophryocystis elektroscirrha-like (OE-like) parasite in field populations and determined its host-specificity (CHAPTER 4), as well as its effects on the fitness, mating behavior and sexual selection in H. armigera (CHAPTER 5). I finally integrated all my results in a general discussion (CHAPTER 6).