Male advertisement call and female preference in sympatric and allopatric midwife toads

Advertisement calls and female preferences in allopatric populations of midwife toads, Alytes obstetricans and A. cisternasii, were compared with those in a sympatric population. These species have simple tonal advertisement calls which overlap substantially in frequency and duration. In both species, the duration of male advertisement calls did not differ between an allopatric and a sympatric population. Playback tests suggested that females in allopatric populations preferentially approach low frequency calls and long calls, exerting directional selection for larger males and males with longer calls. Female A. cisternasii from the sympatric zone did not prefer low frequency calls, which could be made by males of A. obstetricans. Similarly, female A. obstetricans from the sympatric zone did not preferentially approach long calls, which could be made by A. cisternasii males. The differences in female preference between sympatry and allopatry follow the expected direction of reproductive character displacement. Within each species, female preferences differed clearly between sympatry and allopatry while male call characteristics did not. (C) 1997 The Association for the Study of Animal Behaviour.