Data and code from: Disentangling the evolutionary cause-effect relationships of environment, sexual selection and body size with birdsong frequency

This project integrates a large comparative dataset and phylogenetic
information to study the evolution of birdsong across 472 Neotropical
passerine species. The dataset includes acoustic, morphological, and
ecological variables (birdsong_data.csv), additional model coefficients
(coefficients-1.csv), and 100 phylogenetic trees
(birdstrees_100_McTavish.nex). An accompanying R script
(Code_PPA_birdsong-evolution.r) performs all analyses, model selection,
and figure generation. Using these data, the study employs Phylogenetic
Path Analysis to test causal relationships among habitat structure, sexual
dimorphism, morphology, and song frequency parameters. Across all
phylogenies, a single causal structure was consistently supported. The
analyses show that greater tree cover increases minimum, peak, and maximum
song frequencies, while bandwidth remains unaffected. Sexual dimorphism
decreases bandwidth and influences frequency values, whereas morphological
traits impose biomechanical constraints on song frequencies and shape
bandwidth differently. Habitat structure and sexual dimorphism also affect
morphological traits, producing additional indirect pathways that
influence birdsong. Furthermore, tree cover itself impacts sexual
dimorphism, embedding it within a broader causal network. Together, the
dataset and analyses reveal that the evolution of birdsong emerges from
interacting environmental, sexual, and morphological forces. The results
support key hypotheses—including acoustic adaptation, sexual selection,
and morphological constraints—and demonstrate that trait evolution is best
understood through multicausal and phylogenetically informed models,
rather than simple linear associations.