Galápagos finches could be singing a different song after repeated drought—one that leads to speciation

Galápagos finches use their beaks to crush seeds and sing songs, so what happens to their musical trills when their beaks change to respond to new menus available under drought? Jeffrey Podos and Katie Schroeder found that the song might not remain the same after six cumulative future drought events that would likely reshape the finch beak. The projected changes in male mating songs could be so significant that they provide a pathway for ecological speciation, the researchers suggest. The researchers tested this idea by digitally modifying male mating songs of Darwin’s medium ground finches (Geospiza fortis) to sound like they might if beaks grew bigger under one, three or six cumulative future drought events. They then tested these “ghost of finches future” songs by playing them back to today’s male finches, as if the singers of the ghost songs were intruding on the males’ territory. Current males did not show signs of recognizing songs produced after six cumulative future drought events, treating the unseen producers of these songs as if they were no longer mating rivals. The study provides a better idea of how much “ecological change, and matched evolution of beaks and songs, would be required to elevate barriers to reproductive isolation,” the researchers write.