Evolution of divergent daily temporal niches shaped by male-male competition can generate sympatric speciation

Specialisation into different ecological niches can participate to species divergence in sympatry. Here, we focus on the partitioning into different timings of reproductive activities during the day, as observed in many insect species living in sympatry. We thus investigate the evolution of the reproductive activity timing of individuals within populations, using a comprehensive stochastic model. We used a multi-locus model to investigate the evolution of (1) the timing of reproductive activity as a quantitative trait and (2) neutral loci that may generate genetic incompatibilities among divergent individuals. We specifically explore how male-male competition for female access can generate negative frequency-dependence on the timing of reproductive activities and fuel population divergence. Our simulations in finite populations highlight the strong effect of male-male competition and operational sex-ratio on the evolution of divergent temporal niches. They also show how genetic incompatibilities fuel the differentiation among populations with divergent temporal niches, but may impair their co-existence. Our model therefore highlights male-male competition as an important factor shaping the evolution of diel niches, that may fuel sympatric speciation.