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This article examines female asexual reproduction, or parthenogenesis, in Hesiod’s Theogony and argues that it is a symptom of the unprecedented and unparalleled female presence Hesiod inserts into his cosmos. This presence in turn reflects Hesiod’s incorporation of gender difference and conflict as indispensable both to the creation and, paradoxically, to the stability of the universe. Five of Hesiod’s deities reproduce parthenogenetically: Chaos, Gaea, Night, Strife, and Hera, of whom all but the sexually indeterminate Chaos are female. Hesiod’s male gods have no analogous reproductive ability. The parthenogenetic phases of the early goddesses form much of the fundamental shape and character of the universe, while in the case of Hera, parthenogenesis serves initially as an act of defiance against Zeus but ultimately enforces his reign. Parthenogenesis does not have these functions in either the Near Eastern or other Greek cosmogonic traditions, a difference that reflects Hesiod’s greater emphasis on female participation in his succession myth. Yet Hesiod’s cosmogonic narrative, like others, culminates in the lasting reign of a male god, Zeus. In this context parthenogenesis is a manifestation of female creation, which ultimately reinforces the stability of a male sovereign. The relative prominence of parthenogenesis in the Theogony reflects Hesiod’s emphasis on gender difference and conflict as indispensable to a cosmos in which conflict and concord coexist as equal partners in creation and stability.

How asexual reproduction affects genome evolution, and how organisms that are ancestrally sexual alter their reproductive machinery upon becoming asexual are both central unanswered questions in evolutionary biology. While these questions have been addressed to some extent in organisms such as asexual clams, rotifers, ostracods, arthropods, and fungi, the most powerful and direct tests of how sex and its absence influence evolution requires direct comparisons between closely related and otherwise similar sexual and asexual taxa. Here, I quantify the rates and patterns of molecular evolution in the meiosis-specific genes Msh4, Msh5, and Spo11 in multiple sexual and asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail. Because asexual P. antipodarum reproduce apomictically (without recombination), genes used only for meiosis should be under relaxed selection relative to meiosis-specific genes in sexual P. antipodarum, allowing me to directly study how asexuality affects the evolution of meiosis-specific genes. Contrary to expectations under relaxed selection, I found no evidence that these meiosis-specific genes are degrading in asexual P. antipodarum; instead they display molecular patterns consistent with purifying selection. The presence of intact meiosis-specific genes in asexual P. antipodarum hints that the asexuals may maintain the ability to perform meiosis despite reproducing apomictically. Asexual meiotic capability suggests that some meiotic components may persist or acquire a new role in these asexuals.

Abstract In order to explore the mechanisms causing trade-offs between sexual and asexual reproductions, the sea anemones Aiptasia pulchella were taken as objects since they can reproduce by both modes simultaneously. Specimens were reared under different temperatures, photoperiods, and densities. Total weights of lacerates were used as an index of investment in asexual reproduction, whereas gonad weights as an index of investment in sexual reproduction. Sea anemones reared under low temperature (22¢J) reached larger pedal disks and produced larger, heavier lacerates, they also produced heavier gonads than those under high temperature (29¢J). Those reared under long light hours (15¡G9) reached smaller sizes and produced heavier gonads than those under short light hours (9¡G15). But the effect of photoperiod on lacerate size, number and weight are not significant. Interaction effect was not significant between these two factors. Correlation between sexual and asexual investments was not significant, either. In addition, A. pulchella reared under low density (1 sea anemone/beaker) produced more, heavier lacerates and heavier gonads than those under crowding conditions (4 sea anemones/beaker). There was a significantly positive correlationship between sexual and asexual reproduction investments. It seems there was no trade-offs between sexual and asexual investiments of the sea anemone A. pulchella.

This thesis comprises of two published papers and one accepted manuscript, focused on various aspects of liverwort reproduction. Treated aspects include patterns of asexual reproduction, sex ratio and sex-specic pattern in vegetative growth, and patterns of genetic variation and spatial genetic structure of populations differing in availability of substrate on localities and the population connectivity, and consequently in size, density, and prevailing reproductive mode. These characteristics were studied on representatives of the family Scapaniaceae s.l., belonging to the largest liverwort order Jungermanniales. The results showed that asexual propagules were formed and present in course of the whole growing season and can be considered as a sufficient substitution for sexual reproduction. In contrast with the female-biased sex ratio observed earlier in most dioicous bryophytes, unexpectedly high male-biased sex ratio was observed in the aquatic liverwort, which was speculated to represent a strategy to overcome sperm dilution in aquatic environment. In addition, no size differences between female and male shoots were detected, although the evidence for higher cost of sexual reproduction in females was found. The study of population genetic structure has shown that even small and predominantly asexually reproducing populations are important sources of genetic variation. However, we were able to demonstrate notably low levels of gene flow among populations where habitat fragmentation poses a significant barrier to dispersal of diaspores. The fine scale study of spatial genetic structure revealed a strong aggregation of genotypes, particularly in smaller populations, and at the same time showed that asexual reproduction is an efficient mean of maintaining the populations at not only the short distances, given the spatial extent of clones spanning dozens of meters.

Numerous factors can influence the evolutionary fate of mutations. Despite this, we tend to study strong evolutionary drivers, or evolution under simple contexts, in part because they are the conditions we have a means to study. My thesis evaluates novel computational approaches to advance detection, and study, of factors that influence a mutation’s evolutionary outcome. First, I present the novel computational tool AEGIS that I use to detect phylogenetic signals of correlated evolution followed by an experimental approach to evaluate the role of epistasis as a potential cause of correlated evolution among sites associated with antibiotic resistance in Pseudomonas aeruginosa. Second, I developed rSHAPE, a novel in silico approach for experimental evolution with asexual haploids, to complement empirical work by providing a common framework in which to test various evolutionary scenarios. After demonstrating that rSHAPE replicates the expected evolutionary dynamics of de novo mutations, I provide evidence that the common laboratory practice of serial passaging may increase stochasticity of evolutionary outcome. Through my work, I have demonstrated that a marriage of computational and experimental approaches will offer new opportunities to understand how the interaction of evolutionary factors influence the fate of mutations.

The fate of any lineage is contingent on the rate at which its genome changes over time. Genome dynamics are influenced by patterns of mutation and recombination. Mutations as the raw force of variation can be acted on independently during exchanges of homologous genetic regions via meiotic recombination. While molecular evolution in sexual lineages is impacted by both mutation and recombination, asexual lineage fate is primarily influenced by the mutation rate; recombination is often altered or absent in asexuals. Although multiple studies show accelerated mutation accumulation in asexual lineages that have lost recombination, virtually nothing is known about rate patterns when meiosis is retained. Here, I use parasitic wasps in genus Diachasma to investigate genome evolution in a recently-derived asexual lineage. I provide evidence that asexual Diachasma possess a canonical set of meiosis genes as well as high levels of genomic homozygosity. Taken together, these observations support an active, albeit modified, form of meiosis in this asexual lineage. In addition, I present the first documentation of accelerated mutation accumulation in the nuclear genome of a naturally-occurring, meiotically- reproducing organism. If harmful, these mutations could impede asexual lineage persistence and contribute strong support for the long-term benefits of sex.

Along the shores of the Northern hemisphere Fucus (Phaeophyceae) species are a prominent presence, providing substrate, shelter, and food for many species. Fucus evanescens, a non-indigenous species (NIS) in Sweden, and F. radicans, a recently described species that so far has only been found inside the species poor Baltic Sea, are the focus of this thesis. Interactions with enemies (e.g. predators, herbivores, parasites) have been shown to play a role in the success of NIS. The low consumption of Fucus evanescens by the generalist gastropod Littorina littorea in Sweden was found to depend on high levels of chemical defense in the introduced population, not the failure of the herbivore to recognize F. evanescens as suitable food. A survey of the relative abundance of F. radicans and F. vesiculosus and the most common associated fauna along the Swedish Bothnian Sea coast showed that F. radicans and F. vesiculosus are equally abundant throughout the range of F. radicans. The most common associated fauna were found to be more abundant on F. radicans compared to F. vesiculosus.  In Sweden, where F. radicans had lower levels of defense chemicals than F. vesiculosus, F. radicans was grazed more than F. vesiculosus in bioassays. This could, together with other factors, influence the range of F. radicans. Fucus radicans and F. vesiculosus are closely related, recently separated, and growing sympatrically, therefore, possible reproductive barriers between F. radicans and F. vesiculosus were studied. In Estonia F. radicans and F. vesiculosus reproduces at different times of the year. No such clear reproductive barrier was found between the two species in Sweden where they reproduce at the same time and fertilization success and germling survival were the same for hybrids as for F. vesiculosus. Since the high clonality of F. radicans means that the gentic diversity in F. radicans populations is low I investigated how genetic diversity translates to phenotypic diversity in nine traits. Phlorotannin levels, recovery after desiccation, and recovery after freezing showed inherited variation, while the other six traits showed no variation related to genetic diversity. Phenotypic variation in populations of F. radicans will be higher in populations with higher genetic diversity and this might be beneficial to the community. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted.</p>

Since their discovery, transposable elements (TEs) have been regarded either as useful building blocks of genomes, or as "selfish DNA": genetic parasites that exploit the sexual cycle to spread in copy number within populations to the detriment of their hosts. If the "selfish DNA" hypothesis is correct, TEs are expected to deteriorate and be lost from asexual populations. This thesis tests the predictions of the "selfish DNA" hypothesis in four asexual plant species, focusing on patterns of nucleotide diversity and nucleotide substitution. Sequences bearing strong resemblance to known TE families including Ty1/copia, Ty3/gypsy, and LINE-like elements were successfully isolated from all four plant species, and showed patterns of nucleotide substitution consistent with a long history of purifying selection. Stochastic simulations were also conducted, and suggested that this result is expected if the host species has been asexual for less than tens of thousands of generations.

It has been suggested that polyploidization affects the ecological niche of a species, possibly ultimately leading to a shift in the distribution of the species, such as in geographical parthenogenesis. The phenomenon describes the wider distribution and shift of asexuals towards higher altitudes, northern latitudes and more extreme habitats when compared with their closely related sexual relatives. Several hypotheses have been proposed to explain such patterns with lacking empirical evidence because investigations rather focused on single hypotheses, which were rather tested several times independently on multiple organisms than vice versa. Therefore, the present study aimed to tackle the phenomenon of geographical parthenogenesis from multiple angles, i.e. testing several hypotheses simultaneously using Hieracium alpinum as a model system. In the arcto-alpine Asteraceae H. alpinum sexually reproducing diploid individuals occur in a small isolated area in the Eastern and Southern Carpathians, while apomictically reproducing, i.e. asexual reproduction via seeds, triploid plants occupy the remaining and much larger part of the range from the Balkans to the arctic parts of Europe. This implies that asexual triploids have had some fitness / colonization advantage(s), leading to a replacement of sexual diploids...