Conspecific mate recognition in swordtails, Xiphohorus nigrensis and X. pygmaeus (Poecilidae)—olfactory and visual cues

" The swordtails Xiphophorus nigrensis and X. pygmaeus are allopatric sister species. Females of both species prefer X. nigrensis males because these males court while X. pygmaeus males do not. When exposed only to male odours, this mating asymmetry is not maintained; females of both species prefer conspecific mates. When female X. pygmaeus are exposed to both visual and olfactory cues of conspecific and heterospecific males, neither the mating asymmetry nor the conspecific preference is maintained; females fail to exhibit a preference. Xiphophorus nigrensis females do not distinguish between odours of large and small conspecifics, as they do in experiments restricted to visual cues. Thus, species mate recognition is influenced differentially by the independent divergence of cues used in different sensory modalities "