Song-based species discrimination in a rapid Neotropical radiation of grassland seedeaters

Abstract

Acoustic signals among newly diverged taxa have the potential to convey species identity, information that is key to reducing hybridization. Capuchino seedeaters constitute a remarkable example of recently radiated endemic species from the grasslands of South America. Th ey are sexually dimorphic and show striking diff erences in male plumage coloration and song. Contrasting with this divergence in phenotype most species show extremely low neutral genetic diff erentiation and lack of reciprocal monophyly, which is interpreted to be a product of recent common ancestry and hybridization. Here we use fi eld-based playback experiments to test for the fi rst time if males of two species, Sporophila hypoxantha and S. palustris , discriminate between conspecifi c and heterospecifi c song. Using various measures of behavior we fi nd that both species react more strongly to their own songs. Th e response to playback from another southern capuchino cannot be diff erentiated from that of a control song from a more distantly related Sporophila species. Additionally, we did not fi nd evidence for reinforcement as the response of S. hypoxantha did not diff er between individuals that co-occur with S. palustris and those that do not. Our fi nding suggests that song, a culturally inherited trait, may help maintain reproductive isolation between species in the rapid and explosive capuchino radiation.