Although the genetic aspects of mating are a rapidly expanding field of study, little information is available for the genus Ophiostoma. The first MAT information for the genus focussed on only three species and this was as such, hardly representative of the genus. In this study, existing DNA sequence data were used as a starting point to expand the available knowledge on mating genes to other species of Ophiostoma. Ophiostoma quercus, one of the better-studied species of Ophiostoma was the focus of the initial investigation. The heterothallic mating strategy of O. quercus was confirmed and isolates of both mating-types were used for the molecular analysis of the MAT genes. Regions of both MAT idiomorphs were observed in both mating-type isolates. This discovery was unexpected and suggests an unconventional mating organisation for O. quercus as compared to other heterothallic fungal species. Such a system is not unprecedented for fungi, but is unique for the genus Ophiostoma. The primers developed for O. quercus were tested in isolates representing 17 species of Ophiostoma. These primers were used successfully to amplify a large segment of the MAT-2 idiomorph in all isolates tested. This significantly expanded on the amount of data available for the MAT genes of Ophiostoma. Analysis showed that these isolates share a high amount of conservation in the MAT-2 open reading frame. This region of the genome is, therefore, not useful for phylogenetic analyses. However, the availability of primers for the region might facilitate testing of other areas of the full idiomorph for phylogenetic inference. Overall, the results presented in this study represent a significant increase in the knowledge available on MAT genes in Ophiostoma. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Genetics / Unrestricted

Parasitism can be defined as a biological interaction in which one party benefits at the expense of another (Keeton and Gould 1986). However unlike predation, the parasite does not kill its host. In the case of avian brood parasitism, one bird lays its eggs in the nest of a member of its own or another species and then abandons its offspring to the care of its new foster parents. These foster parents or 'hosts' then raise the parasitic young at the expense of their own brood. Brood parasitic birds have reproductive advantages over those which provide parental care for their young because: 1) parental care provided by several fosterers allows a female to produce more successful offspring than she is capable of rearing herself in one season, and 2) parasite offspring are usually distributed among many host nests thereby increasing the probability that at least some offspring will escape predation (Payne 1977). Obligate interspecific brood parasitism, where females only parasitize the nests of other species, is a reproductive strategy adopted by approximately 1% of all bird species and is practiced by members of five families (Anatidae, Cuculidae, Indicatoridae, Icteridae, and Ploceidae). The degree to which interspecific brood parasites reduce host nesting success varies with the reproductive tactics of the parasite. For example, Common Cuckoo chicks (Cuculus canorus) eject eggs and young nest mates from the host nest with the help of an instinctive urge to push out of the nest anything that touches the sensitive shallow depression in the parasitic nestling's back (Lack 1968). Young African Greater Honey-guides (Indicator indicator) stab host nestlings to death with special mandibular hooks that drop off after two weeks of age (Friedmann 1955). In contrast, black-headed duck hatchlings seek only protection and warmth for 1-2 days post hatching and then leave the nest with no further cost to their host (Weller 1968). Finally, Brown-headed Cowbird nestlings intermediately affect host reproductive success by diverting parental resources such as food away from the host's young (Payne 1977). This loss of host fitness results in selective pressure for host defenses against parasitism such as egg ejection (Neudorf and Sealy 1992), clutch abandonment (Burgham and Picman 1989), or increased nest defense early in the nesting cycle (Burgham and Picman 1989, Briskie and Sealy 1989, Neudorfand Sealy 1992). To circumvent these host responses, adaptation in brood parasites has resulted in selective pressure for egg mimicry (Rothstein 1990), egg removal, or shorter incubation periods (Briskie and Sealy 1990, Payne 1977). The Brown-headed Cowbird is the most abundant and widely distributed obligate interspecific brood parasite in North America. Although the breeding behaviour of this bird has been widely studied, most findings are contradictory. The mating system of the Brown-headed cowbird has been described as ranging from monogamous (Laskey 1950, Dufty 1982a, 1982b, Yokel 1986), to promiscuous (Elliot 1980). Most studies also suggest that cowbirds parasitize multiple host species (Friedmann 1929, p 177-188, Jones 1941, McGeen & McGeen 1968, Elliot 1977, Fleischer 1985). However, a few suggest that some individuals may be host specialists (Walkinshaw 1949, McGeen & McGeen 1968). Few of these studies have used genetic techniques to determine the actual mating patterns and to investigate the breeding biology of males and females in a single marked population. The main objective of this study was to use molecular genetic DNA markers as well as behavioural observation to study the mating system and host specificity of a Brown-headed Cowbird population at Delta Marsh, Manitoba. More specifically, my objectives were to: 1) determine whether DNA microsatellite markers are useful for determining parentage in Brown-headed Cowbird populations 2) document the genetic mating system and the patterns of host use by individual females in a population of resident cowbirds. My findings provide the first evidence that microsatellites are useful for high resolution parentage analyses in brood parasitic bird species where there is no A priori information available on male or female parentage. In addition, they are the first to directly quantity the mating system of a Brown-headed Cowbird population and to suggest that individual females are best described as host generalists but may be showing some preference for host nests in one habitat over another. / Thesis / Master of Science (MSc)

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Equitable romantic relationships are relationships in which partners perceive that they are giving benefits to their partner that equal the benefits they receive from their partner (e.g., Walster, Traupmann, & Walster, 1978), and such relationships promote commitment (Rusbult, 1980). But do equity considerations influence observers’ impressions of a romantic couple? In the present study, I tested this possibility by examining observers’ impressions of romantic partners who were mismatched in physical attractiveness (i.e., one partner will be more physically attractive than the other). In this situation, heterosexual observers instinctually categorize the opposite-sex member of the couple as a potential mate and the same-sex member of the couple as a competitor for the potential mate’s affection (e.g., Buss & Dedden, 1990; Fisher & Cox, 2009). Furthermore, observers also conclude that a potential mate who is more attractive than his or her current partner (i.e., the competitor) is not committed to his or her current relationship (Stinson & Reddoch, unpublished data). Thus, when evaluating a romantic couple, I hypothesize that observers’ will demonstrate mating-motivated biased perceptions of potential mates and competitors when the mate is more attractive than the competitor, because such more-attractive potential mates will be perceived as romantically “available.” Participants viewed photos of dating couples who matched in attractiveness, or viewed photos of dating couples where the mate was more attractive or less attractive than the competitor. Participants then rated the potential mates’ and competitors’ status-resources (SR; Fletcher et al., 1999). Results supported my theory of mating-motivated person-perception: Observers derogated the SRs of competitors who were paired with a more attractive (and romantically available) potential mate. / Graduate / 0623 / 0451 / c.joordens@gmail.com

Despite over a century of research, malaria parasites (Plasmodium) still remain a major cause of mortality and morbidity worldwide. In recent years, the application of theoretical principles from ecology and evolutionary biology to the study of these parasites has started to provide insight into variety of fundamental subjects from the evolution of virulence to the facultative strategies (i.e. phenotypic plasticity) that parasites use to maximize their transmission. It is now becoming increasingly clear that to understand and predict population level patterns of virulence and transmission, the processes that occur at the between-host level must be studied in light of the interactions that happen within hosts (between parasites and between parasites and hosts). In this thesis I combine concepts from evolutionary biology and ecology with tools from molecular and cellular biology and evolutionary genetics, which allow me to study rodent malaria parasites at both evolutionary and ecological timescales. The work I present in this thesis has the following four components: 1. Phylogenetics (chapter 2): I applied recently developed phylogenetic methods to a large DNA sequence dataset that I generated, to provide a better understanding of the phylogeny of rodent malaria parasites and investigate how selection has shaped their genomes. I show that all rodent malaria subspecies can be considered species, provide the first time line for the evolution of this group of parasites and demonstrate that most loci are under purifying selection. 2. Hybridization and reproductive isolation (chapter 3): I show that hybridization between two rodent malaria parasites (P. berghei and P. yoelii) can occur, but only occurs at high levels when one of two proteins (P230 or P48/45) is absent from the surface of female gametes, which indicates that these proteins are involved in gamete recognition. I find that P230, P48/45 and P47 (a possible interaction partner) are evolving under positive selection, a feature often observed in gamete recognition proteins of other taxa. Finally, I show that the fertilization success of P. berghei is reduced in the presence of P. yoelii, but not vice-versa, which indicates asymmetric reproductive interference. 3. Sex allocation (chapter 4): I carry the first test of sex allocation’s assumption that immunity impacts on the fertility of Plasmodium male gametocytes/gametes more than on the fertility of females. I show that while the fertility of both males and females is equally affected, males are affected during gametogenesis and females are mostly affected through gamete dysfunction (i.e. gametes can mate but zygotes fail to develop), which is in agreement with the assumptions of theory. In collaboration, I incorporate these effects into sex allocation theory and predict that malaria parasites can minimize the effects of factors that kill gametocytes/gametes by adjusting their sex ratios. On the other hand sex ratio adjustment cannot compensate for gamete dysfunction or zygote death. These results have applied implications for transmission-blocking vaccines. 4. Infection dynamics of mixed-species infections (chapter 5): I develop a series of experiments to test how a focal parasite species (P. yoelii) is affected by competition with heterospecifics (P. chabaudi) and how the interaction between the two species is mediated by immunity and resource availability. I show that P. chabaudi can boost P. yoelii above its single species level (i.e. facilitation) and that this is mediated by resource availability. On the other hand, P. yoelii’s performance can also be hindered in mice that were exposed to a P. chabaudi infection. My results also reveal that host mortality is exacerbated in mixed-species infections of naïve mice, which may be due to an inability of the host to achieve the right balance between the production and the destruction of red blood cells, when dealing with a mixed-species infection. The work I present here tackles fundamental questions concerning the transmission biology and the within-host interactions of malaria parasites The results presented demonstrate the importance of interactions between hosts and parasites and between different parasite species (at the molecular and the whole organism levels) for determining the outcome of transmission, virulence and within-host parasite performance.