Data from: Range-wide spatial mapping reveals convergent character displacement of bird song

A long-held view in evolutionary biology is that character displacement
generates divergent phenotypes in closely related coexisting species to
avoid the costs of hybridisation or ecological competition, whereas an
alternative possibility is that signals of dominance or aggression may
instead converge to facilitate coexistence among ecological competitors.
Although this counter-intuitive process⎯termed convergent agonistic
character displacement⎯is supported by recent theoretical and empirical
studies, the extent to which it drives spatial patterns of trait evolution
at continental scales remains unclear. By modeling variation in song
structure of two ecologically similar species of Hypocnemis antbird across
Western Amazonia, we show that their territorial signals converge such
that trait similarity peaks in the sympatric zone, where intense
interspecific territoriality between these taxa has previously been
demonstrated. We also use remote sensing data to show that signal
convergence is not explained by environmental gradients and is thus
unlikely to evolve by sensory drive (i.e. acoustic adaptation to the sound
transmission properties of habitats). Our results suggest that agonistic
character displacement driven by interspecific competition can generate
spatial patterns opposite to those predicted by classic character
displacement theory, and highlight the potential role of social selection
in shaping geographical variation in signal phenotypes of ecological
competitors.