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This study is the first to quantify pelage sexual dichromatism (PelSD) across the order Primates. The hypothesis that PelSD evolves as a consequence of sexual selection on the pelage color of male primates is considered. Color-corrected high-resolution photographs were taken of primate pelts taken from museum collections, representing primate 83 species. Two measures of color, luminance and hue, were taken for the dorsal and ventral aspects of the trunk of each specimen. These measurements are proxies for the absolute and relative concentrations of melanin(s) in primate pelage. Highly-dichromatic species were identified and the evolution of luminance and hue in males and females of those species was analyzed. Species where male luminance or hue was under selection without concomitant selection on females were considered to be under sexual selection. There was little clear evidence of sexual selection on male luminance in highly-dichromatic species. However, there was substantial evidence of sexual selection on male hue. To determine if male pelage color is an ornament that signals quality and is used by females in choosing mates, fluctuating asymmetry (FA), a proxy for mate choice, was regressed against PelSD. Evidence of trunk pelage as ornamentation (i.e., significant correlation between FA and PelSD) was only observed among platyrrhines. Sexual selection on male hue and a trend toward yellower pelage in males of highly-dichromatic species suggests a shift to phaeomelanin production in those males. Explanations for the observed shift to yellow pelage/phaeomelanin production are explored. / Anthropology

Animals display considerable phenotypic variation in their mating traits, and this variation can have important consequences for the evolution of dimorphic traits between the males and females within a species. In chapter 1, I outline the current state of our understanding of plasticity in reproductive phenotypes, and argue that more work needs to be done to connect the gap between plasticity in mating traits and the outcomes of sexual conflict. Across my four data chapters, I used the fruit fly as a model organism in series of experiments that attempt to better understand how plasticity in mating traits influences the fitness outcomes of both males and females. In chapter 2, I experimentally manipulated the outcome of a fighting experience, and found that males who win a previous fight have higher precopulatory reproductive success, but losers perform better in post-copulatory areas. In chapter 3, I manipulated the amount of competition that a male experiences and found that females mated to males who experience competition produce more early-life offspring but live shorter lives compared to females mated to males that experience no competition. In chapter 4, I manipulated the intensity of sexual conflict that a female experiences and found that males mated to females who experience high conflict have lower pre- and post-copulatory reproductive success compared to males mated to females who experience low conflict. In chapter 5. I manipulated the degree of sexual aggression that a female experiences, and found that females that experience harassment and mating from a male that displays high sexual aggression is subsequently less choosy compared to females that experience a less aggressive male. Finally, in chapter 6, I discuss the significance of my results as they relate to the evolution of reproductive traits in males and females. / Dissertation / Doctor of Science (PhD) / Considerable phenotypic variation exists both within and across species. Within species, one source of this variation is phenotypic plasticity, the ability for an individual to alter its phenotype based on environmental influences. When it comes to sex, both males and females in many species exhibit striking variation in their reproductive behaviour as a result of plasticity. However, the causes and consequences of this variation are not well understood. Throughout my doctoral dissertation, I used the fruit fly as a model to explore how various social experiences such as fighting, competition, sexual harassment, and mating shape the subsequent reproductive behaviour of males and females, and quantified the evolutionary consequences of this variation. The results of my studies have important implications for understanding the evolution of various behavioural strategies such as aggression and mate choice.

Adaptation to local environments via natural selection is a powerful mechanism for population divergence and likely one of the primary causes of speciation. To understand how specific habitats shape local adaptation, it is helpful to study closely-related populations from widely differing ecosystems that have not had sufficient time to diverge by genetic drift. Throughout the following chapters I examine the distribution of morphological, behavioral, and reproductive phenotypes within and between two subspecies of the swamp sparrow. These two populations, the tidal salt marsh endemic Melospiza georgiana nigrescens and the nominant inland subspecies, M. g. georgiana were incompletely isolated from each other following the retreat of the Wisconsin glaciation. Since that time the increased nest predation, temperature, season length, salinity and tidal flow of the coastal marshes relative to inland wetlands has resulted in a number of adaptations among coastal sparrows due to natural selection, sexual selection, and phenotypic plasticity. Specifically I examine the habitat preferences of the coastal plain swamp sparrow, the difference in clutch size between the two subspecies, the rates of extrapair fertilization relative to male quality, the ecosystem-specific interactions between natural and sexual selection on plumage badges, and the role of conspecific attraction in nest placement. The environmental differences of the tidal salt marsh have played strong roles in the local adaptation and divergence of coastal plain swamp sparrows from their freshwater ancestors. Many of these divergent mechanisms may be similar among other tidal marsh endemics, although some (especially those related to sexual selection) may be specific to the swamp sparrow. In general, however, we see that the added environmental challenges of tidal ecosystems strongly alter selection regimes on a terrestrial vertebrate inhabiting this dynamic ecotone. The swamp sparrow system can further increase our understanding of how the interplay between environmental resources, sexual selection, and natural selection affects the local adaptations leading to evolutionary divergence. / Ph. D.