Cultural evolution in Rufous-and-white Wrens (Thryophilus rufalbus): Insights from acoustic and genetic analyses
Acoustic signals play an important role in the evolutionary process. Studying variation in acoustic signals and the evolutionary forces that act on acoustic evolution will help to clarify the role that acoustic divergence plays during speciation. The acoustic signals of birds have been well studied, although most historical research has focused on the acoustic traits of males living at temperate latitudes. Recent work shows that female song is more common than previously thought, particularly in the tropics, and that female song is the ancestral trait in birds. Therefore further research on the acoustic traits of females is necessary to examine the evolutionary significance of animal vocal signals. In this dissertation I compare patterns of cultural evolution in male and female Rufous-and-white Wrens, and I examine the evolutionary forces that act on male and female acoustic signals. To achieve this goal, I combine acoustic and genetic analysis to quantify genetic differentiation, migration, and dispersal patterns and determine the role that these factors have on acoustic variation. In addition I incorporate ecological data and use a sound transmission experiment to explore the effect that ecological variation has on acoustic evolution. My results indicate that males and females exhibit similar patterns of acoustic variation, suggesting that similar evolutionary processes act on both male and female songs. Specifically, acoustic differences between populations appear to arise due to cultural drift or cultural selection, as opposed to genetic variation and ecological selection, as has been shown in other species. Males and females also show cultural differences, including lower song-sharing rates by females, greater inter-annual variation in the acoustic structure of female songs, and sound transmission differences. These patterns indicate that there may be sex-based differences in selection pressures acting on songs. Additionally, my results show that dispersal is female-biased in Rufous-and-white Wrens and therefore cultural differences between sexes may arise as a result of dispersal differences between the sexes. Collectively, my results provide further insight into the acoustic variation of male and female birds, and expand our knowledge of female song and the vocalizations of tropical animals.
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