While the existence of costs of mate choice is well accepted, the effects that these costs have on mating systems and the evolution of mate choice are controversial. The aim of this thesis is to explore a range of different types of costs, including costs of being choosy (using guppies, Poecilia reticulata) and costs of mating with attractive males (using house crickets, Acheta domesticus), and investigate how these costs influence female mating behaviour, sexual selection on males and the evolution of mate choice. I use a range of experimental techniques to investigate these questions including: comparisons of feral populations of guppies (Chapter Two), laboratory experiments that manipulate the social (sex ratio, density; Chapters Three and Four) and physical (water current; Chapter Five) environment in which guppies live, genetic paternity analysis and multivariate selection analysis (Chapter Four). I also conduct longitudinal studies of house crickets that estimate the net fitness consequences (Chapter Six) and indirect effects (Chapter Six and Seven) of mating with attractive males. My results demonstrate that the physical and social environment of individuals are important in determining the costliness of both sexual display and mate choice, and thus influence the mating behaviour of males and females. These differences in mating behaviour are often thought to lead to differences in sexual selection on males. My study of the effects of operational sex ratio and density on multivariate sexual selection, however, indicates that differences in behaviour may not necessarily translate into differences in selection. In contrast to predictions of recent theory, my results also indicate that although there are many costs to being choosy and to mating with attractive males, these may be outweighed by indirect benefits. Hence, despite direct costs of choice, mate choice may evolve via indirect benefits to females. Indirect benefits that are often neglected in sexual selection studies, that I show to be important in determining the net fitness of mating with attractive males, include the attractiveness of sons and the mate choice decisions of daughters. These results highlight the importance of examining the consequences of mate choice over multiple generations.

Thesis (M.S.)--Ohio University, November, 2009. / Release of full electronic text on OhioLINK has been delayed until September 1, 2010. Title from PDF t.p. Includes bibliographical references.

According to Darwin, any inheritable traits that enhance fitness (i.e. survival and reproductive success) would be adaptive in a given environment, and therefore subject to natural selection. Some traits that enhance reproductive success but not necessarily survival may, however, evolve through the process of sexual selection. The importance of sexual selection has been intensively studied in “higher animals” birds, mammals and insects but has largely been neglected in “lower animals” such as gastropods. Using two mangrove snails, Littoraria ardouiniana HEUDE 1885 and L. melanostoma GRAY 1839 (Littorinidae) as model species, this thesis documents their various reproductive traits and the occurrence of sexual selection, in an attempt to understand how these animals optimize their fitness. Being one of a few gastropod families that live closely associated with mangrove habitats, various adaptive reproductive traits are likely to have evolved in the genus Littoraria. The two Littoraria species exhibited several, contrasting, reproductive traits (e.g. reproductive mode; length of reproductive season; seasonal fecundity and egg- or larvae-releasing rate), which may represent species-specific strategies to optimize reproductive success. Both species adopted mucus trail following as a mate-searching strategy; with males being able to discriminate the trails laid by conspecific females and trail orientation during the mating season. Since these two snails mate in the complex habitat of mangrove tree canopies, incorporating some cue into mucus trails to aid mate recognition would increase potential encounter rates and hence reproductive success. 1D proteomic techniques identified two potential pheromones in the trail mucus of female L. ardouiniana, but further investigations are needed to confirm their possible role as sex pheromones. Evidence for sexual selection was found in L. ardouiniana through male mate choice and male-male competition. Large male L. ardouiniana showed a preference for mucus trails laid by large (= more fecund) females, but this preference was not seen in small males, suggesting a size-based male mate preference. Males of this species also mated with larger females for a longer duration and they showed physical aggression (i.e. they pushed each other) when they encountered a female. These sexual selection mechanisms may drive size-assortative mating patterns in littorinid species and in other animals. Conversely, L. melanostoma exhibited no obvious male mate preference or male aggression. Such differences in sexual selection patterns from L. ardouiniana were proposed to be a result of differences in operational sex ratio and variation in female quality. As many gastropods show similar mating behaviour to littorinids (i.e. trail following, shell mounting and copulation), sexual selection may operate in a comparable manner in other gastropods. By revealing the complexity of sex roles of males and females (e.g. the mutual occurrence of male mate choice and male-male competition) and condition-dependent male mate preference in these mangrove snails, this thesis has contributed to a missing link between sexual selection and the “lower animals” and provides new insights into the operation of sexual selection in animals. / HKU 3 Minute Thesis Award, Champion (2012) / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

The origin and maintenance of phenotypic variation has generated considerable interest among students of functional morphology, sexual selection and behavioral ecology. In particular, hybridization has been suggested as a phenomenon which may generate novel phenotypic variation. In this dissertation I focus on the Xiphophorus birchmanni - X. malinche hybrid system to assess the role of hybridization in altering behavioral, morphological, sexual and non-sexual traits. I determine the relationship between the sword sexual ornament and body condition to support previous work which suggests that the sword is an inexpensive means to increase apparent size. My findings support the prediction that, while body size is condition-dependent, the sword is not. I show a trend toward hybrid populations displaying increased phenotypic variance and reduced phenotypic integration in sexual ornaments and body size. These findings provide evidence for a potential answer to a central question in the study of sexual selection, that of reduced genetic and phenotypic variance in sexual ornaments as the result of persistent direction selection generated by female choice. I take advantage of reduced phenotypic integration in hybrids allowing the evaluation of locomotor performance across a broad range of multivariate trait values. Sexual ornaments did not impair swimming performance per se. Rather, the sword negatively affected performance only when paired with a sub-optimal body shape. I evaluated how natural hybridization changes the relationship between boldness and anti-predator response. In poeciliid fishes, bold individuals have increased survival in the presence of predators. This non-intuitive observation may result from bold individuals being more likely to engage in anti-predator behaviors. Counter to my prediction, bold individuals were less likely to perform a fast-start response to a predator threat. This correlation was consistent among populations and species but was only significant in hybrids. My findings suggest that hybridization could influence correlations between behavioral traits in a manner similar to that documented for morphological traits.

Thesis (Ph.D.) - University of St Andrews, April 2009.

Thesis (Ph. D.)--University of Washington, 1981. / Vita. Bibliography: leaves [246]-271.

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Although most strepsirrhines do not exhibit apparent physical signs of sexually selected traits, researchers have suggested that olfactory communication is sexually selected. The goal of this thesis is to (1) review sexual selection theory with an emphasis on sensory communication, and (2) test whether olfactory communication is sexually selected in strepsirrhines. I examined the relationships between primate mating systems and several measures of olfactory communication in 22 species: scent marking rates, the number of scent marking methods, and the volume of the main and accessory olfactory bulbs. I also evaluated qualitative data on olfactory communication in three lemur species to determine whether they meet the criteria of a sexually selected trait. Polygynandrous and monogamous species did not significantly differ from each other in scent marking rates, scent glands, or volume of the main and accessory olfactory bulbs. Three species of strepsirrhine met all criteria of having sexually selected olfactory traits, suggesting that polygynandrous lemurs are subject to sexual selection on several levels of olfactory communication. / text