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The sexual reproduction of four gorgonian corals, Ellisella robusta, Subergorgia suberosa, Subergorgia mollis and Bebryce indica at Wanlitong, a non-upwelling area, and Talauko, an upwelling area, in south Taiwan were compared in order to understand their reproductive strategies. Four species were gonochoric. E. robusta, S. suberosa and S. mollis were broadcasting spawners with annual reproductive cycle. The reproductive mode of B. indica was not certain and it may reproduce several times within one year. The mean diameter of mature oocytes of E. robusta, S. suberosa, S. mollis and B. indica was 360, 322, 461, and 312 £gm, respectively. Their fecundity was 3.2, 1.4, 1.1, and 2.0 oocytes/polyp, respectively. Corals with longer oogenesis duration produce larger mature oocytes. The three broadcasting species spawned in September, October and November after the seasonal disturbances. It may be advantageous for the survival of their offspring. The reproductive traits of E. robusta, S. suberosa, and B. indica were similar between Wanlitong and Talauko populations. It suggests that reproductive traits of theses species may be not influenced by upwelling.

To date little information has been collected on the pollination biology of <i>Ailanthus altissima</i> (Mill.) Swingle (tree-of-heaven), an invasive exotic in the U.S. This study was conducted to determine the insect pollinator fauna visiting <i>A. altissima</i> and to study general pollinator visitation patterns associated with the tree's nectar profile. A list of taxa visiting trees within each of three sites was developed from collected insects. Overall, visitor assemblage was dominated by the soldier beetle <i>Chauliognathus marginatus</i> with large numbers of ants in the genera <i>Formica</i>, <i>Prenolepis</i>, and <i>Camponotus</i>. No major diurnal pattern was found for visitation of insect pollinators using instantaneous counts. The nectar composition, concentration, and amount of total sugars in the flowers of <i>A. altissima</i> and how these are related to tree gender and time of day were determined. Nectar was found to be sucrose-dominant with lower, but nearly equal amounts of fructose and glucose. Total amounts of sugar in male and female blossoms were not statistically different, however higher concentrations of sugar were found in males (40.7%) than in females (35.3%). No difference was found over time. Nectar production and removal in trees was studied by comparing bagged flowers with flowers open to insect visitation. Bagged flowers were higher in overall sugar than open flowers, however, this was not constant across all times and gender. / Master of Science in Life Sciences

Asexual species which never incorporate novel genetic material from other lineages will go extinct faster than sexually reproducing species, because adaptive variability may be lower and a larger number of harmful mutations may accumulate. One form of asexuality, androgenesis, results in offspring that are clones of the father. Both androgenetic and sexual species are found in the clam genus Corbicula. I used genetic data to explore why there are multiple species of androgenetic Corbicula, and whether genetic exchange occurs between species. I found that in North American locations where two invasive, androgenetic species co-occur, restriction digest mapping of rDNA failed to detect recent nuclear exchange. However, in these same locations, mitochondrial markers were shared between species. In places where only one species was found, mitochondrial markers were unique to that species. This suggests androgenetic clams are able to parasitize eggs of closely related species. Whereas maternal mitochondria are retained in the fertilized egg, maternal nuclear chromosomes are expelled, and the mother incubates male clones of another species. To look at possible gene exchange over the long term, I compared phylogenetic tree topologies of one mitochondrial and two nuclear markers from multiple sexual and androgenetic species. Since several androgenetic species share similar or identical alleles, androgenesis seems to have evolved relatively recently in Corbicula. However, since different androgenetic species also have divergent alleles not shared between species, genetic capture of maternal nuclear DNA from other species may rarely occur. This rare capture of genetic material from other species may permit the long-term persistence of androgenesis in Corbicula. / text

The brown macroalgae Fucus radicans is endemic to the Baltic Sea, but little is known about this newly described species. This thesis investigates the ecology and role of F. radicans within the species poor Baltic Sea ecosystem. The thallus of F. radicans had a more complex structure but was smaller than F. vesiculosus, the other important foundation species with which it grows in sympatry at several sites. The variability of the associated flora and fauna communities of these two Fucus species, however, was explained by the thallus size, not the complexity. Comparisons between the populations of F. radicans in the Bothnian Sea with those in Väinameri Sea on the Estonian coast, showed that the Estonian thalli were smaller, less complex and lacking the numerous adventitious branches which occur extensively in the Bothnian Sea populations. The distribution of F. radicans in Sweden is limited to the Bothnian Sea coast. The low salinity at the northern limit prevented successful fertilization, while increased salinity did not restrict F. radicans but improved its reproductive success. The southern distribution limit was instead shown to be negatively impacted by a combination of grazing and competition. The asexual reproduction through settling of detached fragments was favoured by high light levels and high temperature in laboratory conditions. Re-attachment occurred by basally formed rhizoids but settling also occurred through a calcium-rich substance, seemingly secreted by the fragment. Genetic spatial distribution of F. radicans showed a dominance of a few widespread clones both within and between sites with an intermingled rather than clustered pattern. The extensive female clone, common in most sites, is most likely old and several clonal lineages have derived from her.  Although more clearly expressed in the clonal populations, the macroscopic sexual dimorphism discovered appears to be a species specific trait in F. radicans. This thesis presents further insight in F. radicans role within the Baltic Sea ecosystem and its value as a study species for adaptation, clonality and speciation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p>

Sex and meiosis are ubiquitous in eukaryotes as the primary mode of reproduction. This suggests that despite the theoretical energetic advantages of asexual reproduction, organisms capable of sexual reproduction are at a much greater long-term evolutionary advantage. Rotifers, a group of microinvertebrates, offer unique opportunities to examine the evolution of sex due to their extensive proliferation, successful adaptation to a wide variety of ecological niches, and the diversity of reproductive modes represented in the group. The cyclically parthenogenetic monogonont rotifers have overcome constraints on the loss of sexual reproduction in order to frequently transition between sexual and asexual generations, making them a powerful system with which to address the maintenance of sex in animals. Obligately asexual bdelloid rotifers appear to have thrived without sex for tens of millions of years, a period of time much longer than expected given the hypothesized advantages of sexual reproduction. However, the molecular nature of sex and parthenogenesis is poorly understood in any rotifer species. To expand our knowledge of the molecular mechanisms of monogonont reproduction, we sequenced genomes of two distantly related species, Brachionus calyciflorus and Brachionus manjavacas and identified over 80 homologs for genes involved in meiotic processes. Several of these genes have undergone duplication events specific to the monogonont lineage, including genes with known roles in regulation of cell cycle transitions during meiosis. In addition, global gene expression patterns were determined using obligate parthenogenetic (OP) and cyclical parthenogenetic (CP) strains of B. calyciflorus. Quantitative comparison of expression between these strains revealed differentially expressed genes specific to sexual and asexual reproduction in this species, including genes related to dormancy/resting egg formation, meiosis, and hormone signaling pathways that are thought to be involved in the induction of sexual reproduction in monogononts. Finally, we analyzed gene expression in bdelloid rotifers for evidence of sexual reproduction or the utilization of meiotic genes under conditions inducing high levels of recombination. Through this work, we have established molecular markers for sexuality and asexuality in monogonont rotifers, and used these markers to evaluate reproduction in bdelloids. The data generated specifically allows for more informed analyses of the evolution of cyclical parthenogenesis and rotifer reproduction. Furthermore, this work extends the use of monogononts as a model system for addressing broader questions regarding the evolution of sexual reproduction.

In Plato’s Theaetetus, when Socrates explains his pedagogical practice, he claims that he practices the art of midwifery, the very same art as his mother. Similarly, in the Symposium, when Socrates praises Eros (love or sexual desire), he draws on the words of his teacher, Diotima of Mantinea. Diotima told him that “all human beings are pregnant.” (206c) In both cases, Socrates’ descriptions of coming to know rely on verbs usually used to describe the physical workings of women’s bodies. What do pregnancy and giving birth capture about coming to know? This dissertation argues that Plato’s metaphors of pregnancy and birth present knowledge acquisition as a generative process that is interpersonally informed and collaborative. Pregnancy is used to describe a generative power that begins as part of oneself and is developed over time through engagement with other people. Other scholars have interpreted Plato’s metaphors of sexual reproduction as an erasure of the feminine. By contrast, my approach is rooted in attending to the particular context in which these metaphors are used and the female knowers associated with these metaphors. With this focus, I find that Plato’s depictions of Diotima and midwives draw on the particular circumstances surrounding women at the time. In chapters one and two, I offer a reading of Diotima’s speech that begins with her status as a foreign woman in classical Athens. I use this historical context to argue for a generative understanding of the metaphors of pregnancy and birth. I examine how the focus on feminine verbs of pregnancy and birth persists throughout the ladder of love, particularly in interactions that are informed by the needs of others. The theme of giving birth culminates in the philosopher educating another in a way that is interpersonally informed. As a result of this close reading, I argue that Socrates’ description feminizes the philosopher who strives toward knowledge. Chapter three argues that Plato uses this feminization to critique the male-dominated cultural scripts surrounding pederasty. These cultural scripts treat wisdom or knowledge as something the lover contains and gives to the beloved in exchange for sexual favors. Opposingly, when Socrates claims that he is a midwife for young men, he presents himself as someone who enables his interlocutors to better understand what is developing within themselves. Socrates and his interlocutor collaborate in this generative process. Chapters four and five focus on this practice of midwifery, first as the sort of expertise practiced by Socrates and his mother, and then as it influences the generative power of the birthing person. The dissertation ends by contextualizing my reading alongside other claims about Plato on women. / 2026-09-30T00:00:00Z

The transition to multicellularity is a major step in the evolution of complex life. The first steps in this transition are poorly understood because multicellularity evolved long ago, and transitional forms have been lost to extinction. Previous studies developed a novel microbial model system in which simple multicellularity could be evolved de novo (Ratcliff et al., 2012). By evolving our snowflake yeast to undergo sexual reproduction we hypothesized that sex created variation in key multicellular traits, which spurs multicellular adaptation. In our 'snowflake yeast' model system, two traits are of central importance: cluster size, and programmed cell death (apoptosis). Apoptosis previously evolved to regulate cluster size, by acting as break points within clusters, allowing them to modify the size and number of multicellular propagules they produce. In prior experiments, this only develops after yeast have evolved to form large clusters. Prior experiments in the lab demonstrated that the longer snowflake yeast have been evolving, the greater the fitness benefit provided by sex. Here we examine whether this is due to sex creating greater amounts of diversity in the traits of post-sex offspring in more highly evolved multicellular yeast, allowing post-recombination offspring to 'fine tune' their multicellular traits. By using flow cytometry, we collected data on our multicellular traits. By gathering the biomass mean of the cluster size in each population and staining the cells with propidium iodide to determine the apoptotic tendencies of our cells we were able to compare our outcomes to the pre-sex ancestor, and we determined there was no increase in variation. Although apoptosis did not have an increase in variation due to sex, it created a variation in cluster size; the variation was seen in the population W8. This still supports our hypothesis that sex creates variation in multicellular traits, which allows for rapid adaptation.

Como tentativa de elucidar os fatores ambientais que controlam a plasticidade fenotípica floral de Catasetum fimbriatum Lindley, iniciaram-se estudos fenológicos, vegetativos e anatômicos da espécie, através do acompanhamento de 45 indivíduos, sendo que trinta destes indivíduos foram coletados e posteriormente envasados, enquanto os demais foram mantidos e observados em seu ambiente natural, nas árvores do Campus ESALQ/USP, permitindo assim, traçar correlações ecológicas entre os três tratamentos instalados, com quinze indivíduos cada. O primeiro tratamento foi montado em casa de vegetação onde predominou intensa luminosidade, altas temperaturas e baixa umidade relativa do ar. O segundo tratamento foi submetido a baixa intensidade luminosa, menor temperatura e a uma umidade relativa do ar mais elevada em relação ao primeiro. O terceiro tratamento foi mantido nas condições naturais. Ao final do experimento, pôde-se constatar a grande adaptabilidade da espécie aos diferenciados ambientes, através da formação de ecótipos, os quais tornaram-se visíveis devido a diferenças apresentadas pelos individuos principalmente na quantidade de brotos. Quanto ao trimorfismo sexual, mesmo não tendo havido a ocorrência de flores diclinas femininas, o estudo anatômico constatou a presença de agregados celulares com características meristemáticas nos ovários e ginostêmios das flores, os quais, acredita-se, caso fossem estimulados pelo ambiente durante um período necessário para definirem a expressão sexual da espécie, possivelmente através de um aumento nos níveis endógenos de etileno, permitindo desta forma a formação de flores diclinas femininas e flores monoclinas. / As attempt of elucidating the environmental factors that they control the plasticity floral fenotipic of Catasetum fimbriatum Lindley, fenological, vegetative and anatomical studies of the species began, through of the accompaniment of 45 individuals. Thirty of these individuals were collected and put in the vases later. The other ones 15 already existed naturally in the trees of the Campus ESALQ/USP, allowing like this, to trace ecological correlations among the three installed treatments. The first fifteen individuals, they were conditioned at vegetation house where intense brightness prevailed, high temperatures and it lowers relative humidity of the air. Such treatment was entitled treatment 1. The other collected individuals that were put in the vase, and that they constituted the treatment 2, they were submitted the low luminous intensity, to a smaller temperature and a relative humidity of the highest air. The last fifteen individuals, presented the natural conditions of survival of the species, and they constituted in that way, the treatment 3. At the end of the experiment, the great adaptability could be verified of the species to the differentiated environments, through the ecotipes formation, which became visible due to differences presented mainly by the individuals in the amount of sprouts. With relationship to the sexual, same trimorfism not having had the occurrence of feminine diclinous flowers, the anatomical study verified the presence of cellular closters with meristematic characteristic in the ovaries and ginostemeus of the flowers, the ones which, If they were environmently stimulated by the period of necessary time, possibly through an increase in the levels etylene endogenous, they would interfere in the sexual expression of the species contributing to the appearance of feminine diclinous flowers and monoclinous flowers.

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.