Behavioral interference between species can influence a wide range of ecological and evolutionary processes. Here we test foundational hypotheses regarding the origins and maintenance of interspecific territoriality, and evaluate the role of interspecific territoriality and hybridization in shaping species distributions and transitions from parapatry to sympatry in sister species of North American perching birds (Passeriformes). We found that interspecific territoriality is pervasive among sympatric sister species pairs, and that interspecifically territorial species pairs have diverged more recently than sympatric non-interspecifically territorial pairs. None of the foundational hypotheses alone explain the observed patterns of interspecific territoriality, but our results support the idea that some cases of interspecific territoriality arise from misdirected intraspecific aggression while others are evolved responses to resource competition. The combination of interspecific territoriality and hybridization appears to be an unstable state associated with parapatry, while species that are interspecifically territorial and do not hybridize are able to achieve extensive fine- and coarse-scale breeding range overlap. In sum, these results suggest that interspecific territoriality has multiple origins and that interspecific territoriality and hybridization together can have striking impacts on species ranges.

These data were collected through literature and database searches. Most data were collected for each species, and then the absolute value of the difference between species pairs was calculated for certain traits (or a correlation or other pairwise similarity measure was used when relevant). We report these species differences in traits as well as sympatry measures in this dataset.

README.csv describes the data in sistertaxa_dataset.csv. The analysis.R file contains code to generate the figures and tables in the paper. The binomial_covariate.R file is a file with functions used in analysis.R. 

The data contain a few missing values but most rows are complete. Each row represents one species pair.