Sensory-driven sympatric speciation is observed and demonstrated in a wide range of animals, from invertebrates (insects) to vertebrates (fishes and amphibiansis). It is based on changes in mate preferences of individuals for particular individuals within a single population that display behavioral traits or specific visual, olfactory and auditory stimuli. The choosy sex is the female (but males are choosy in a considerable number of cases). This selective mating makes possible the reproductive isolation of a group (population) of individuals from the rest of, and within, the original population even though both populations are physically in contact and not isolated from each other. Owing to the neuro-cognitive mechnism of the mating preference, the new population can maintain and develop a separate gene pool within the original population and over time develop/or not postzygotic isolation in sympatry.
Mate preference is a behavioral trait and, as such, it is a function of the activity of neural circuits determining that behavioral trait. We are still far from a real understanding of the neuro-biological mechanisms of changes in neural circuits for mate preferences but we know for sure that no change in genes are involved in the process. Hence, it is a perceptual neural, epigenetic mechanism that by preventing interbreeding of a group of individuals within a larger population enables the formation of new species in sympatry, a phenomenon unexplainable from a genetic point of view.