From courtship to egg-laying: how chemical cues and experience shape reproductive strategies in Drosophila melanogaster

Reproductive behaviors are essential for animal evolution and species survival, requiring insects to evaluate diverse sensory cues when making key decisions such as mate choice and oviposition. This thesis examines how chemical cues and experience influence these reproductive decisions in female Drosophila melanogaster, an ideal model organism due to its short life cycle and easy maintenance. Because these flies feed, mate, and lay eggs on overripe or fermenting fruits, food-related odors are highly relevant to their reproductive ecology, yet the role of natural fruit odors has remained less explored. Here, it is shown that fruit volatiles can be passively adsorbed onto male bodies after exposure to different fruit substrates and that these odors influence female mating preference without changing male pheromone levels. This suggests that males can increase their attractiveness through environmental odors, revealing a rapid, non-genetic ecological mechanism that may contribute to sexual selection. Oviposition represents another critical reproductive step, as females must choose a suitable substrate for offspring development by integrating olfactory, gustatory, and tactile cues, including nutritional information such as sugar type and concentration. Here, it is demonstrated that fructose is the most preferred sugar for egg-laying and also supports the best larval performance, while optimal concentrations differ among sugars. The correlation between female preference and larval survival supports the “mother knows best” hypothesis. Finally, this thesis shows that oviposition preferences are not only innate but can also be modified by experience: females later preferred the substrate on which they had previously laid eggs, demonstrating that egg-laying experience itself shapes future choices. Together, these findings show that chemical cues and learning help female Drosophila optimize mating and oviposition, thereby improving reproductive success.