This thesis proposes an algorithm to enhance the convergence speed of genetic algorithm by modifying the function flow of a simple GA. Additional operators, such as asexual reproduction, competition, and livability, are added before the survival operation. After adding these three operators to the genetic algorithm, the convergence speed can be increased. Experiments indicate that simulations with the proposed algorithm have a 47% improvement in convergence speed on the traveling salesman problem. As for the graph coloring problem, the proposed algorithm also has a 10% improvement. Also, since these operators are additional parts to the original GA, the algorithm can be further improved by enhancing the operators, such as selection, crossover, and mutation.

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.

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>

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...

Chronic bioassays were conducted on the annelid Aeolosoma headleyi Beddard (l888) to determine the effects of heavy metals on asexual reproduction. Bioassays were conducted with the chloride and sulfate salts of zinc, copper, cadmium, cobalt, and nickel. Additionally, chromium, as potassium dichromate, was tested. Of these metals, only two, zinc chloride and copper sulfate, significantly stimulated reproduction at or below 0.01 ppm of the metal. All metals inhibited reproduction at high concentrations and none, except the two above, had any significant effect on reproduction at the sublethal concentrations tested. Hydrogen ion concentrations between 6 and 10 units had no effect on reproduction. The effects of the metals were not due to pH or osmotic effects. Subsequent studies were conducted with zinc chloride to determine its effect on zooid scissiparity. As zinc concentrations increase, the time for first zooid scissiparity decreased. Second bud formation was inhibited by zinc levels greater than 0.1 ppm. Normally the worm exhibits paratomy (release of zooid with a developed cephalic region). Above 7.0 ppm zinc, the worms also exhibit architomy where the cephalic region is not developed prior to scissiparity. / Master of Science

Le changement climatique et l’augmentation des températures globales perturbent l’abondance et la distribution de milliers d’organismes, aquatiques et terrestres, et certains écosystèmes sont particulièrement sensibles à ces changements environnementaux. L’augmentation de température est la principale menace au maintien des populations de coraux, véritables ingénieurs écologiques de ces écosystèmes. Bien que la recherche sur les récifs coralliens se soit d’abord attachée à l’étude des coraux adultes, de nombreuses informations manquent sur la reproduction sexuée et asexuée, et leur rôle dans la conservation et restauration récifale. Le premier axe de ma thèse s’est donc construit sur la réponse des jeunes stades de vie à l’augmentation de température, pour d’abord évaluer les modifications de leur performance et ensuite évaluer dans quelles mesures les jeunes stades seraient capables de s’acclimater à des conditions de températures plus élevées. Au travers de différentes expérimentations en laboratoire sur le genre Acropora, j’ai ainsi mis en évidence 1) une résistance thermique importante (+2-3°C au-dessus des températures ambiantes) des gamètes face à l’augmentation de température, 2) une résistance thermique différente entre spermatozoïdes et ovocytes: ovocytes < spermatozoïdes, 3) et la mise en évidence du rôle majeur de l’environnement dans lequel se rencontre les gamètes une fois libérés, sur la qualité et la quantité de la fécondation. Enfin, j’ai identifié les conditions optimales thermiques de pré-exposition des gamètes pour maximiser leur succès de fécondation. Bien qu’un intérêt croissant soit porté sur la reproduction sexuée ces dernières années, l’utilisation de la reproduction asexuée demeure la méthode la plus utilisée pour restaurer les récifs coralliens, plus connue sous le nom de bouturage. Ainsi le second axe de ma thèse a cherché à mettre en évidence la plasticité phénotypique des coraux en cultivant des boutures provenant de 3 espèces dans 3 environnements différents et en analysant leur taux de croissance, leur état de santé et leur survie. Cet axe a pu montrer qu’il existait des différences à plusieurs échelles, entre espèces, mais aussi au sein d’une même espèce. Mes travaux montrent qu’une sélection des individus basée sur l’étude de la plasticité phénotypique de certains traits d’histoires de vie comme la croissance ou l’état de santé dans des environnements variables permettrait d’améliorer l’efficacité de la restauration récifale. Ainsi le choix des individus au sein d’une même espèce afin de réaliser du bouturage (reproduction asexuée) et le conditionnement de la phase de vie gamètes (reproduction sexuée) peut permettre d’augmenter l’efficacité des méthodes de restaurations tout en nous donnant des informations nouvelles sur la biologie et la physiologie des coraux scléractiniaires face aux changements environnementaux. / Climate change and increasing temperature impact abundance and distribution of thousands of organisms, aquatic and terrestrial, and some ecosystems are particularly sensitive to these global changes. Increasing temperature is the principal threat for coral populations, which are ecological engineers of coral reef ecosystems. While research on coral reefs has first sought to study adult corals, data are still lacking on early life stages of corals. As sexual and asexual reproduction may play a key role in the conservation and restoration of coral reefs, my doctoral research aims to better understand changes on sexual and asexual reproduction in the face of rising temperature. The first axis of my Ph. D. was built on the response of early life stages to increasing temperature, in order to assess whether pre-exposure of early life may improve their ulterior performance. Among the different experiments performed on the genus Acropora, I highlighted 1) a high thermal tolerance (+2-3°C above ambient temperature) of gametes, 2) a higher sensibility of oocytes than sperm to rising temperature exposure, and 3) the pivotal role of gamete thermal history on fertilization output. Finally, I identified optimal pre-exposure conditions in order to maximize fertilization success. While an increasing interest in sexual reproduction was observed these last years, asexual reproduction and fragmentation still remain the main tool to restore damaged reefs. Thus, in the second axis of my doctoral project, I investigated the phenotypic plasticity of corals by growing 3 different species of corals across 3 different environments. Their growth rates, health status and survival probability were determined. Results from this axis showed that differences were observed at the interspecific and intraspecific levels. This work revealed that a selection based on phenotypic plasticity among different life-traits (growth rates and health status) and different environments should allow to increase coral reef restoration strategies. Hence the selection of individuals (asexual reproduction) in a species based on coral common garden experiment allow to identify individuals of interest to use as restoration biological materials. Additionally, thermal pre-conditioning of early life stages (sexual reproduction) is another way to increase efficiency of restoration measures in the face of rising temperature. My doctoral research provided new information regarding physiological and biological processes of scleractinian corals facing environmental changes and proposed new solutions for restorations based on sexual and/or asexual reproduction.

Although genomes are perhaps the single most important element of living systems, why they feature such striking variation and how this variation is maintained within and across natural populations remains unclear. One of the most common and important means by which genomic variation is generated is ploidy elevation. While polyploidy has been implicated in the remarkably successful radiations of angiosperms, teleost fish, and amphibians, the phenotypic consequences of changes in ploidy level are poorly understood, especially in animals. I use a large, multi-year common garden experiment to identify potential life history costs and benefits of polyploidy and asexual reproduction, a trait often associated with polyploidy, in Potamopyrgus antipodarum. This snail is well suited for studying ploidy variation and sex because diploid sexuals and triploid and tetraploid asexuals frequently coexist, allowing us to use comparisons of sexuals to asexuals and triploid to tetraploid asexuals to study both the effects of ploidy elevation and sex. I detected a strong negative correlation between growth rate and time to maturity and found that sexual P. antipodarum grew and matured significantly more slowly than the polyploid asexuals. Sexual P. antipodarum were also more likely to die before achieving reproductive maturity than their asexual counterparts. By contrast, there were no apparent life history differences between triploid and tetraploid asexuals, indicating that direct phenotypic benefits of ploidy elevation are unlikely to explain the relatively rapid growth and maturation of asexuals. My results suggest that ploidy elevation does not inevitably confer phenotypic consequences, that reproductive mode influences life history trait expression, and that sexual P. antipodarum persist in many natural populations in spite of substantial life history disadvantages.