Earlier studies implicate interlocus sexual conflict as having important evolutionary consequences in Drosophila serrata but it has never been directly studied. I quantify sexual conflict and its divergence between two laboratory stocks using a full factorial manipulation of male population, female population, and level of male exposure to track longevity and fecundity of individual females. Evidence of strong sexual conflict, as well as divergence of male harm and female resistance between populations, was found. The relationship between environmental complexity and sexual conflict was then explored using a combination of behavioural observations and a factorial experiment to again track longevity and fecundity of individual females. Increased complexity was associated with decreased sexual activity and increased lifespan in females, although effects on fecundity were less clear. Overall, my studies combine to provide initial data for characterizing sexual conflict in Drosophila serrata and shed light on important considerations for its study.

Master of Science / Department of Entomology / Jeremy L. Marshall / Males providing females with gifts in order to mate is not a novel occurrence. Indeed, depending on the taxonomic system, males may provide gifts ranging from dead insects, to nutritious ejaculates to even subjecting themselves to cannibalistic feeding. Interestingly, while the burden of the costs of these gifts is primarily carried by the male, net fitness of providing or receiving such gifts must be positive for both sexes, if these gifts are to be maintained in a population. If this is not the case, and sexual conflict has exerted a cost-benefit imbalance between the sexes, then the expectation is that the system will evolve towards the reduction of nuptial gift giving. Here, utilizing the Allonemobius socius complex of crickets where females benefit greatly from cannibalizing male blood as a nuptial gift, we explore the possibility that sexual conflict is acting on gift size. To do this, we assess the gift-size distribution, and their associated fitness functions, for twelve populations that span the phylogeny and geographic distribution of this complex. We find that gift-size distributions are shifted towards small or no gifts in the majority of populations. Moreover, fitness data suggest that males providing a small or even no gift are equally successful to their large gift-giving counterparts. Taken together, the population profiles indicate that at least half of these populations are evolving towards the near or complete loss of these cannibalistic gifts – a predicted, but previously undocumented, outcome of sexual conflict. We also assess the speed at which sexual conflict is acting to alter gift size distributions in populations by comparing gift sizes between different time points in populations and across phylogenetic history. The implications of these results are discussed relative to antagonistic coevolution of behavioral traits and sexual conflict theory in general.

Sexual conflict can occur whenever the evolutionary interests of males and females differ, and when sexually antagonistic selection acts upon traits shared between the sexes, one or both sexes can be constrained from reaching their phenotypic optima. This intralocus sexual conflict can be characterised by a tug-of-war of allelic replacement until it is resolved, but examples of well-characterised sexually antagonistic loci are rare. This thesis investigates the basis and dynamics of intralocus sexual conflict over insecticide resistance at the Cyp6g1 locus in Drosophila melanogaster, and wing colouration in Drosophila simulans. In D. melanogaster, the Cyp6g1 locus is the site of a series of insecticide resistance alleles, one of which is sexually antagonistic when back-crossed to the old isogenic lab strain Canton-S. I investigated the presence of sexual conflict over this same allele in a recently collected and genetically heterogeneous population. I found evidence of balancing selection on resistance (Ch. 2) that could not be explained by overdominance or sex-specific dominance (Ch. 3). However, balancing selection could be explained by resistance conferring increased fecundity to females (Ch. 2-4), and decreased reproductive success to males (Ch. 4). This male cost can in turn be explained by a negative genetic correlation between reproductive success and Cyp6g1 expression (Ch. 4), possibly influencing levels of reproductive investment (Ch. 2). Additionally, I explored the dynamics of the sex-specific fitness effects of resistance across three Cyp6g1 alleles back-crossed to a single genetic background. I found no evidence of sexual antagonism, but revealed that the cost of resistance increased with more derived alleles, and that all alleles were more costly to females (Ch. 5). After decades of strong selection imposed by insecticide use an unresolved sexual conflict persists at the Cyp6g1 locus despite sexual dimorphism in resistance, and it does not appear that more derived Cyp6g1 alleles are necessarily involved in mediating this conflict. Wing interference patterns (WIPs) are a newly discovered trait subject to female mate choice in Drosophila. I explored the potential for intralocus sexual conflict over WIPs by measuring WIP traits from males and females from populations of D. simulans evolved under relaxed or elevated sexual selection. In response to sexual selection male WIPs evolved to be brighter, higher contrast, and shifted to longer wavelengths of light, but there was no associated response to selection in females (Ch. 6). While WIPs did not appear to be constrained from detectably responding to selection by acute intralocus sexual conflict, male WIPs from the relaxed selection regime were similar to female WIPs, suggesting a cost to sexually selected WIPs that may be indicative of sexually antagonistic selection. IASC is pervasive and can influence a wide range of fundamental evolutionary processes including sexual selection, speciation, and extinction. The research presented in this thesis adds to a body of evidence that sexual dimorphism does not necessarily resolve IASC, and documents the first evidence that WIPs do not appear to be subject to acute IASC and can evolve in response to sexual selection.

The ‘good genes’ model of sexual selection predicts that sexual and natural selection should act concordantly. However sexual selection can favour alleles in males that are costly when expressed in daughters, placing the two in opposition. The relationship between natural and sexual selection depends on the nature of genetic variation for fitness. Laboratory adaptation may deplete sexually concordant fitness variation, overestimating sexually antagonistic variation and obscuring good genes. I investigated sire-offspring fitness correlations in Drosophila melanogaster populations expected to differ in their levels of sexually concordant fitness variation. In maladapted populations, successful sires produced fitter daughters than unsuccessful sires; this pattern was reversed in adapted populations. Several generations later, successful sires in both population types produced lower fitness daughters than unsuccessful sires, consistent with predictions. However, subsequent generations revealed no effect of sire status on daughter fitness, highlighting the difficulty in testing predictions on the evolutionary dynamics of fitness heritability.

The ‘good genes’ model of sexual selection predicts that sexual and natural selection should act concordantly. However sexual selection can favour alleles in males that are costly when expressed in daughters, placing the two in opposition. The relationship between natural and sexual selection depends on the nature of genetic variation for fitness. Laboratory adaptation may deplete sexually concordant fitness variation, overestimating sexually antagonistic variation and obscuring good genes. I investigated sire-offspring fitness correlations in Drosophila melanogaster populations expected to differ in their levels of sexually concordant fitness variation. In maladapted populations, successful sires produced fitter daughters than unsuccessful sires; this pattern was reversed in adapted populations. Several generations later, successful sires in both population types produced lower fitness daughters than unsuccessful sires, consistent with predictions. However, subsequent generations revealed no effect of sire status on daughter fitness, highlighting the difficulty in testing predictions on the evolutionary dynamics of fitness heritability.

Since much of the existing research which points to the low validity of the Draw-a-Person technique has used differentiation of diagnostic categories as a criterion, this study will be restricted to a consideration of the Draw-a-Person technique as a means for discriminating between a group of individuals who manifest conflicts in the area of sexual adjustment and a control group which does not show these conflicts in any appreciable amount.

Master of Science / Department of Entomology / Jeremy L. Marshall / Sexual conflict is a process that occurs when the evolutionary interests of the sexes is not aligned. The theory began with Darwin in the 1800’s. His observations of sexual dimorphism and traits which did not seem to follow the rules of natural selection led him to the theory of sexual selection. Sexual selection resolved some of the issues which were noted in the evolutionary processes he observed but not all of them. For example, it did not explain traits which increased the male optimum fitness while decreasing the female optimum fitness. It was decades before the concept of sexual conflict was formulated, and even longer before the underlying mechanisms were understood. Sexual conflict is different than sexual selection and there are ways to differentiate which of these processes have occurred in a population. The main forms of sexual conflict are intralocus and interlocus conflict. These involve the interactions between alleles in the genome of the sexes. Intralocus conflict involves conflict at a single locus in the genome while interlocus conflict involves conflict between different loci. Interlocus conflict has been more extensively studied due to its association with sexually antagonistic coevolution (SAC). SAC draws the attention of scientists due to the possibility it is related to the fundamental biological process of speciation. Sexual conflict targets certain traits at defined periods in the mating process. These periods include first, the precopulatory stage which is before the act of copulation begins. Second, there is the stage during copulation but before fertilization of the embryo. Finally, there is the postcopulatory postzygotic stage which is after copulation has ended and fertilization has occurred. Each of these points in the process of mating has traits or behaviors which sexual conflict may target. This review concludes with a proposed experiment to determine if sexual conflict is occurring in a group of four genera of mosquitoes. The experiment utilizes the attributes of sexual conflict to differentiate between other processes. A major component is the consequence of mating systems on selective processes to determine if sexual conflict is involved in the evolution of male accessory gland proteins.

In D. melanogaster, resistance to DDT is conferred by the upregulation of a cytochrome P450 enzyme, CYP6G1. Resistant flies have tandemly duplicated Cyp6g1 alleles that possess the LTR (Long Terminal Repeat) of an Accord retrotransposon inserted in the cis-regulatory region, 291bp upstream of the transcription start site. This DDT resistance allele (DDT-R) has been shown to have pleiotropic fitness benefits for female flies in at least one genetic background and with evidence of sexually antagonistic selection at this locus. In this thesis, I first review the role of transposable elements in conferring insecticide resistance and the evidence to date regarding the pleiotropic effects of DDT-R in D. melanogaster. By conducting life history and behavioural tests on flies of two genetic backgrounds I examine the sex-specific effects of expressing DDT-R in the absence of DDT. Finally I develop a single locus population genetics model based on these sex-specific effects and test the model using replicate laboratory populations. The first main finding is that DDT-R incurred a male mating cost that depended on the genetic background in which DDT-R was found and that this cost coincided with strong epistasis between genetic background and DDT-R that influenced male size (Chapter 3). Following on from this result, it was confirmed that the effect of DDT-R on male size does contribute to lowered mating success but does not fully explain this fitness cost (Chapter4). Additionally, resistant males were found to have a lowered rate of courtship behaviour driven by aborted chasing of females and lower male-male aggression than susceptible males (Chapter 4). Fitness assays in wild caught strain females revealed that DDT-R confers a fecundity increase but unlike previous work, no offspring viability increases were detected (Chapter 5). Thus as with male costs, specific pleiotropic female fitness benefits to resistance depend on genetic background. Modelling of DDT-R using a simple single-locus approach (Chapter 6) provides, for the first time, a unifying explanation for past and present DDT-R frequencies in nature and in old laboratory populations. The model is consistent with an old origin for the original DDT-R mutation held at low equilibrium frequency through balancing selection of a sexually antagonistic nature. It is also consistent with continued near fixation of DDT-R long after discontinued use and matches empirical observations in laboratory populations of the Canton-S background.

During the evolution of sex, different sexual conflicts arise. Sexual conflicts reduce fitness of the opposite sex. That is why several mechanisms have evolved to resolve them, which leads to rapid and unpredictable co-evolution of male and female traits involved in reproduction. This rapid co-evolution of male and female reproductive traits driven by sexual conflict can further lead to reproductive isolation resulting in speciation.             I used the hermaphroditic fungus Neurospora crassa, which has two mating types, as a model organism. Mating types are proxy to sex, because both are needed for sexual reproduction, but they are not limited to either sex role. However by using male pheromone knock-out lines, I created an evolutionary setup, where either mating type is forced to adapt to its restricted sex role. After 21 sexual generations of adaptive co-evolution, I tested if mating types had adapted to the assigned sex by measuring fitness (production of sexual spores called ascospores). I used three evolutionary setups (lines): Δccg4 lines, where mat A is female and mat a is adapted to the male role, Δmfa1 lines, where conversely mat A is adapted to the male role and mat a is female, and wild-type lines used as controls, where both mating types have maintained and adapted to both sex roles. And discovered one Δccg4 line, which indeed adapted to the newly assigned sex roles. At generation 15 and 21 I obtained mixed results for the presence of sexual conflict by correlating male and female fitness in hermaphroditic partner mat a in this line, however I found a sexual conflict also in the asexual growth, where male role is associated with increased, but female role with decreased mycelium growth rate. This work will further allow to study genomic mechanisms underlying this adaptation.

<p>Sexual conflict occurs when female and male fitness interests diverge. In a social system characterized by aggressive sexual coercion and the risk of infanticide, female chimpanzees (Pan troglodytes) respond to this conflict by exhibiting an exaggerated sexual swelling that advertises sexual receptivity while concealing the exact timing of ovulation. Sexual swellings impose significant costs, yet can persist into pregnancy. Records from long-term studies of eastern chimpanzees (P. t. schweinfurthii) in Gombe National Park, TZ, and Kibale National Park, UG, provide data on postconception swellings, while data on group composition and behaviors such as mating, grooming, and aggression are drawn from the Gombe database only. Throughout, I use linear mixed models to simultaneously test multiple effects while controlling for repeated measures of individuals. In Chapter 1, I tested whether variation in females’ vulnerability to infanticide and aggression predicted the amount of swelling during pregnancy. In Chapter 2, I examined female-male relationships across reproductive states to ask whether females can better gain benefits and avoid costs by affiliating promiscuously with all males, or by investing in relationships with preferred males. Finally, I analyzed metabolites of reproductive hormones using urine samples from pregnant females in both populations to build a hormonal profile of postconception swellings. Swellings during pregnancy increase female-male association, and are caused by the same basic hormonal mechanism as preconception swellings, though they occur in a very different hormonal milieu. Females at greater risk of infanticide and intrasexual aggression swell more during pregnancy. Females mate promiscuously before conception, but during pregnancy and lactation, preferentially groom with males that are likely to protect them from aggression and infanticide. Based on these and other findings, I conclude that postconception swellings in chimpanzees are an adaptive response to sexual conflict.</p> / Dissertation