Geographic variation in song and genetics in the Townsend's Warbler (Setophaga townsendi)

Bird song is shaped by both genetic and cultural processes, presenting a particularly tractable system for understanding the connection between communication and reproductive barriers that drive diversification. Song dialects—or differences in song structure across geographic space—can act as signposts of cultural differences between populations, which may also indicate genetic differences in the population. The Townsend’s Warbler (Setophaga townsendi) is a species with geographic variation in mitochondrial genetic signatures. I investigate if concurrent variation occurs in song and nuclear genetic signatures, by describing the geographic variation of song and nuclear DNA across Townsend’s Warbler range. I quantify distinct song types and patterns across Townsend’s Warbler populations, along with patterns of genetic variation across their range using genotype-by-sequencing data. If genetic and cultural processes are tightly linked, I expect song to vary between regions of genomic differentiation. I demonstrate that individuals have a repertoire of at least two distinct song types—consistent with the two-song-type pattern common in Parulid warblers—but find this pattern is less evident in a range-wide comparison. There is extensive variability in Type I song, whereas Type II song is more stereotyped across the range. There is little distinct grouping that coincides between song and the isolation-by-distance pattern in the nuclear DNA. A mismatch between song and genetic patterns suggests that song divergence is not predicted solely by genotype. By characterizing the within-species variation in song and genetic structure, we can expand our understanding of the dynamic interplay between cultural traits and population structuring.Science, Faculty ofZoology, Department ofGraduat