The interplay of sexual selection and hybridization can drive sexual radiation

Sexual selection is considered a major driver of species diversification, but little is known about whether and how sexual selection may contribute to the incipient stages of speciation and sexual radiation. Based on evolutionary simulations, here I propose that an interplay of sexual selection and hybridization can drive the rapid formation of multiple species with diverse exaggerated sexual displays within a lineage. Existing theories suggest that sexual selection can cause evolutionary dynamics with multiple stable equilibria, with which multiple species with distinct sexual displays and mate preferences can persist stably. However, the stability of each equilibrium hinders the formation of new species from an existing species that is already occupying one of the stable equilibria. In such situations, hybridization between phenotypically similar but genetically distinct lineages can catalyze speciation. Hybridization can generate genetic variation by recombining alleles from different lineages. I provide evolutionary simulations demonstrating that hybridization that gives rise to genetic variation in mate preference can modify the sexual selection regime to open up opportunities for the evolution of sexually selected displays toward previously unoccupied stable equilibria. Hybridization thus can trigger evolutionary shifts between alternative evolutionary equilibria that sexual selection generates, driving the incipient formation of sexual radiation.