Patterns of song evolution and sexual selection in the oropendolas and caciques

Although oscine bird song is widely thought to have evolvedunder the influence of sexual selection, few studies have usedphylogenetic comparative methods to investigate how these vocalizationshave changed historically. In the present study, we use a molecularphylogeny based on mitochondrial sequence data to reconstructvocal evolution in the oropendolas and caciques, an oscine groupwith diverse taxon-specific song patterns and a wide range inlevels of sexual size dimorphism. Our reconstructions show thatlarge changes in song organization and structure have occurredon branches of the phylogeny with relatively high levels ofsize dimorphism. The particular vocal components that changed,however, often differed in different phylogenetic lineages.These patterns indicate that sexual selection has had importantinfluences on song evolution in these birds, but has targeteddifferent components of song in different taxa. Our resultsprovide insight into how sexual selection influences bird songand suggest directions for future research to uncover the behavioralmechanisms driving vocal evolution.