Genetic Composition Is Unrelated to Song Content in a Wild Passerine.

Birdsong is a key sexual signal that varies substantially among individuals and populations. Understanding whether song similarity reflects genetic similarity is central for evaluating its role in sexual selection, population divergence and evolutionary dynamics, although partial vocal learning can obscure this relationship in many species. Assessing the relationship between song and genetic variation requires accounting for both spatial and temporal heterogeneity in both traits, so despite its importance, the genetic architecture underlying song traits, and in particular song content, remains poorly understood. Here, drawing on 15 years of song recordings and extensive SNP (Single Nucleotide Polymorphism) data, we investigate whether song similarity among males reflects their genome-wide genetic similarity in the collared flycatcher (Ficedula albicollis), a migratory passerine with complex and variable songs. After accounting for geographic and temporal separation, we found no strong association between male song similarity and genome-wide genetic similarity. Moreover, males belonging to the same genetic cluster did not seem to produce more similar songs than those from different clusters. Additionally, genetic distance was unrelated to either geographic or temporal distance, and geographic proximity did not predict song similarity. Instead, song content similarity decreased with increasing temporal separation between recordings, consistent with cultural evolution. Together, these findings indicate that biologically relevant song features are primarily shaped by cultural processes rather than genetic architecture, enabling rapid, flexible responses to environmental changes.