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Abstract

The evolution of social behavior has long been a focus of research for behavioral ecologists and evolutionary biologists. From brief interactions to highly complex associations between individuals of cooperative or colonial species, understanding sociality has been central to the studies of sexual selection, evolution, and adaptation. The Maluridae, the fairy-wrens, emu-wrens and grasswrens, is a family of highly social birds native to Australia and New Guinea. While these species have been a model for cooperative breeding, they also exhibit characteristics atypical for classical cooperatively breeding species. Most notably, these species have extremely high rates of extra-pair paternity, and exhibit variation in the identity (sex) or and the role that auxiliary individuals take in the social group both within and between species. These characteristics, along with variation in species range overlap and variation in ecology makes this family ideal for examining the evolutionary drivers of sociality. My dissertation research addresses the evolution of sociality, as well as plumage dimorphism in fairy-wrens, and highlights evolutionary transitions in this model group. In my first data chapter, Different modes of evolution in males and females generate dichromatism in fairy-wrens, I use evolutionary models to examine how plumage evolution differs between males and females and relate plumage dichromatism relates to latitude. In my second data chapter, Heterospecific sociality mediated by song discrimination in fairy-wrens, I document an example of heterospecific sociality between splendid and variegated fairy-wrens and experimentally test discrimination between co-resident, neighbor and foreign heterospecifics by song. In my final data chapter, Helping behavior and promiscuity in the variegated fairy-wren: sex specific effects of auxiliary members, I characterize the social behavior, helping behavior, and extra-pair paternity of one of the variegated fairy-wren. Together, this work highlights the necessity of continued studies of sociality within this family, and suggests varying evolutionary pressures leading to greater or lesser degrees of sociality, even to extremes of sociality across species, are at play within the fairy-wrens.

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