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How parasites influence the population dynamics of their hosts depends on 1) theproportion of individuals that carry the infection in the population, 2) what type of individuals aremost susceptible to infection and 3) the fitness effects of infection. In this study I first investigate thefrequency of malaria strains transmitted in the African winter quarters or at the European breedinggrounds in collared flycatchers (Ficedula albicollis). I then zoom in on the relationship between avianmalaria infection status and condition, expression of sexually selected ornament and reproductiveperformance of male collared flycatchers. I found that female flycatchers are more likely to beinfected than males and that both sexes have a large bias towards infection with European strains ofmalaria. Infected male flycatchers have higher reproductive success and tend to have largerornaments but there was no detected relationship between malaria infection and male condition.This is the first example, that I am aware of, of a positive relationship between malaria infection andreproductive success.

This thesis is an evaluation of the hypothesis that the spennathecae of spiders affects the sperm precedence patterns in a predictable way (Austad 1984). Spermathecae come in two varieties: cul-de-sac and conduit. Cul-de-sac spennathecae, according to the hypothesis, are supposed to lead to second male sperm priority and conduit to first male sperm priority . The hypothesis was evaluated both directly and indirectly. Direct measurements were made of paternity in two species, Pholcus phalangioides and Tetragnatha montana, both of which are cul-de-sac species. It was found that P. phalangioides complies with the predicted precedence pattern and thus does not disprove the hypothesis. This second male priority pattern was despite a much shorter mating time by second mating males. In T. montana no precedence pattern was found, with equal likelihood of first or second mating males of gaining paternity. There was in T. montana a possible influence of the duration of mating affecting the precedence pattern, with longer mating males gaining a higher paternity no matter what order they mated in. It is discussed whether or not this is due to sperm loading or genitalic stimulation (Eberhard 1985). Indirect evaluation of the hypothesis included an analysis of mating behaviour in Zygiella x-notata which is a conduit species and was chosen as a comparison to the two cul-de-sac species. In Z. x-notata it was found that there was no difference between mating duration in first and second mating males. Mating persistence is thus the same in first and second mating males, suggesting that the males cannot detect that the female is a denuded resource to second mating males. Hence first male priority may not be a factor in this species. Other indirect methods of evaluating the hypothesis involved charting the incidence of mate-guarding and mating-plugs. The expected pattern of mate-guarding was for conduit species to pre-mate guard and for cul-de-sac species to post-mate guard, because of the predicted sperm precedence patterns associated with the spermathecae. The predicted pattern was not found. In the case of mating-plugs it was predicted that these should be deployed by cul-de-sac species because it is in these species that second males are able to usurp paternity to a large extent. The opposite pattern was found with mating-plugs of various design being utilized by conduit species. It is postulated that mating-plugs are the mechanism by which first male priorities are established in conduit species, where this pattern is found. The absence of plugs in cul-de-sac species is possibly the reason that second males can cuckold. The additional data collected since 1984 reveal that patterns of paternity found in spiders seem to be more complex than was originally assumed by Austad (1984). Spermathecae are species-specific in character and this may reflect a species specificity in sperm precedence patterns. Thus the conduit I cul-de-sac dichotomy may not reflect a useful prediction of paternity patterns.

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

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

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