Postmating reproductive barriers contribute to the incipient sexual isolation of US and Caribbean Drosophila melanogaster

Abstract

The nascent stages of speciation start with the emergence of sexual isolation. Understanding the influence of reproductive barriers in this evolutionary process is an ongoing effort. We present a study of Drosophila melanogaster populations from the southeast United States and Caribbean islands undergoing incipient sexual isolation. The existence of premating reproductive barriers have been previously established, but these types of barriers are not the only source shaping sexual isolation. To assess the influence of postmating barriers, we investigated putative postmating barriers of female remating and egg laying behavior, as well as hatchability of eggs laid and female longevity after mating. In the central region of our putative hybrid zone of American and Caribbean populations, we observed lower hatchability of eggs laid accompanied by increased resistance to harm after mating to less related males. These results illustrate that postmating reproductive barriers acting alongside premating barriers in a complex secondary contact zone. Furthermore, our findings suggest hybrid incompatibilities, likely due to the nature of genomic admixture of populations in the area, are influential even at the early phases of sexual isolation.