Vocal behaviour, geographic variation, and the evolution of song in Troglodytes wrens

Animal acoustic signals are important for mate attraction, resource defense, and species recognition. When vocalizations diverge between closely related groups they can play a key role in speciation. Therefore it is important for biologists to describe the vocalizations of wild animals, to document geographic differences in acoustic signals, and to evaluate the relationship between acoustic variation, genetic variation, and ecological variation. In this dissertation, I study the songs of New World wrens in the genus Troglodytes , small territorial songbirds distributed throughout the Americas, including several oceanic islands, that are well known for their loud, complex songs. I conducted observational and experimental studies of Troglodytes wrens in the field, and morphometric studies of museum specimens. In chapter 1, I provide background information on the topics in the subsequent chapters. In chapters 2 and 3, I provide the first empirical description of the vocal behaviour of two species of Troglodytes wrens from Mexico: Brown-throated Wrens and Cozumel Wrens. In chapter 4, I quantify geographic variation in songs of wrens within the House Wren species complex--a group of birds noted for taxonomic controversies--demonstrating that several subspecies show acoustic differentiation on par with many species. In chapter 5, I show that patterns of geographic variation in vocalizations predict genetic divergence, and that the fine structural characteristics of Troglodytes songs, as well as birds\u27 responses to playback of those songs, are associated with phylogenetic relatedness. In chapter 6, I show that songs vary at a continental scale and that several aspects of wren vocalizations are closely associated with both phylogenetic differentiation and ecological variation. Taken together, my results suggest that songs of Troglodytes wrens exhibit substantial geographic variation, that they encode species identity that is used to distinguish conspecific rivals, and that they show evidence of adaptation to ecological features. My research stands as an example of how acoustic signals can be use for resolving taxonomic problems. My findings enhance our understanding of how acoustic diversity originated and how fine structural characteristics are constrained, adapted, and maintained through evolutionary lineages