Wide-scale conversion of tallgrass prairie to row-crop agriculture has spurred restoration of this endangered ecosystem. At the onset of restoration, a matrix of native plant species is sown into former crop field and includes warm-season (C4) grasses, cool-season (C3) grasses, legumes, and a large variety of herbaceous forbs. Increased demand for native seed due to a greater number of areas targeted for restoration has increased use of C4 grass cultivars by restoration practitioners. Cultivars are selectively bred to display traits such as increased productivity and digestibility, thus highlighting their original use in rangelands of the Great Plains. C4 grasses have a mutualistic relationship with arbuscular mycorrhizal fungi (AMF). In remnant tallgrass prairie, AMF can increase C4 plant uptake of belowground resources (e.g., water, soil P) by increasing root surface area. It is unknown if AMF colonization varies between seed source (cultivar or non-cultivar) of C4 grasses used in restoration and if this further affects plant biomass. Intraspecific variation in AMF colonization between two dominant warm-season prairie grasses was tested in two established prairie restoration experiments, both having plots seeded with either C4 cultivars or non-cultivars. To test for effects of seed source and AMF colonization on plant biomass, a greenhouse experiment was designed using two source populations (cultivar and non-cultivar) of two species (Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash) and soil collected at each field restoration (Kansas and Illinois). To suppress activity and colonization of AMF, a fungicide (Allban Flo: Thiophanate Methyl) was applied to half of the containers. Warm-season (C4) grass cultivars had greater or equivalent biomass production than non-cultivars at the onset of field restoration and also in the greenhouse. Furthermore, cultivars generally had less or equivalent root colonization by AMF and dependence on fungicide-free soil was greater in cultivars to retain increased accrual of biomass. It was, however, not possible to determine the role of AMF in plant biomass production as fungicide did not successfully reduce AMF root colonization in cultivars or non-cultivars, with one exception. It is critical that an effective AMF-suppression treatment be established in these types of studies. Future experiments should validate supposed effectiveness of the newly-recommended fungicide (Topsin-M) in population sources of warm-season prairie grasses and also apply it to the soil at time of planting in greenhouse studies. In the field sites, adjacent soil cultivation may have contributed to greater AMF biomass more so than surrounding remnant prairie. Future research identifying species composition of AMF at these sites is necessary to clarify differences in biomass. Despite greater plant biomass in cultivars, soil nutrient availability remained equivalent between source populations in general. Available N and P were not less in soils grown with cultivars, however soil inorganic N was inversely related to root length colonized by AMF, suggesting a role of AMF in N transfer from soil to plant. Soil P was not different between source populations likely due to legacy effects of agricultural fertilization, thus limiting a well known benefit of AMF symbiosis, at least at the onset of restoration. Non-target effects of fungicide application were observed (e.g., changes in available N) and effectiveness of AMF suppression was questionable. Fungicide lowered pH and increased N availability in soil as indicated by main effects of application and a positive relationship between pH and inorganic N across species. Fungicide application either 1) decreased N uptake by soil microorganisms (possibly including AMF) or 2) increased competition for adsorption sites and/or solubility of total inorganic N as pH changed, thus making this nutrient more available in the soil solution. Future examination quantifying indirect effects of fungicide application on soil chemistry should also be considered to better elucidate role of AMF in plant growth and soil nutrient availability between cultivars and non-cultivars of warm-season grasses used in tallgrass prairie restoration.

L’étude des nystagmus du nourrisson est difficile pour des raisons méthodologiques. La plupart des études sont donc réalisées chez des adultes et a posteriori. Ces études chez l’adulte ont permis la révision des classifications des nystagmus infantiles, avec la consolidation des concepts de syndrome du nystagmus précoce et de nystagmus de type latent. La séméiologie et l’étiopathogénie des nystagmus du nourrisson – notamment des formes comportant un élément vertical et des formes transitoires – reste donc à étudier. Dans ce but : 1. Nous avons développé de nouvelles techniques d’enregistrement des mouvements oculaires chez les nourrissons, utilisables dans le cadre d’une consultation. Elles incluent de nouveaux stimuli, un appareil d’enregistrement des mouvements oculaires spécialement conçu pour le nourrisson et de nouvelles méthodes d’analyse statistique du signal. Nous avons vérifié la faisabilité de ces enregistrements chez 28 nourrissons atteints de nystagmus. 2. Nous avons étudié systématiquement 32 cas de nystagmus de type spasmus nutans, classiquement considéré comme une entité bénigne idiopathique, avec un examen clinique complet, une imagerie cérébrale, une électrophysiologie visuelle et des enregistrements oculo-moteurs. Dans 53,1% des cas, le spasmus nutans était le symptôme d’une autre maladie : neurologique (34,3%), notamment des gliomes du chiasma (21,9%), ou rétinienne (12,5%). Une atteinte des voies visuelles antérieures est probablement en cause dans la physiopathologie des spasmus nutans. 3. Huit cas de nystagmus ayant conduit au diagnostic de gliome des voies optiques (GVO) ont été également enregistrés et étudiés. L’âge d’apparition du nystagmus allait de 2,5 à 10 mois. Le GVO était toujours chiasmatique et constituait une sous-population spécifique. Le nystagmus était toujours de type spasmus nutans. Les enregistrements oculo-moteurs montraient : une fréquence entre 2,7 et 5 Hz, une morphologie sinusoïdale du nystagmus, une dissociation et une dysconjugaison particulière, avec une opposition de phase (180°) entre les oscillations des deux yeux dans le plan horizontal mais une correspondance de phase dans le plan vertical, à l’origine d’un mouvement semblable à un mouvement de convection. Rarement et brièvement, le rapport de phase changeait. Ces caractéristiques orientent vers des oscillations dans le système des vergences, possiblement la conséquence d’une atteinte des afférences sensorielles des centres du contrôle vergentiel dans le tronc cérébral, secondaire au GVO et survenant pendant la période sensible du développement visuel. 4. Cinq cas de nystagmus upbeat chez des nourrissons avec des rétines et une imagerie cérébrale normale ont été étudiés. Le nystagmus était observé en décubitus et électivement déclenché par des rotations de la tête en position allongée. Dans tous les cas, une résolution spontanée était observée après quelques mois d’évolution. Les caractéristiques de ce type de nystagmus suggèrent une participation du système otolithique, suivie d’une recalibration secondaire des circuits vestibulo-oculaires. En conclusion, le développement de techniques d’enregistrement des mouvements oculaires adaptées aux nourrissons aide à la compréhension de l’étiopathogénie de variétés mal décrites de nystagmus, notamment dans les cas comportant un élément vertical et dans les cas transitoires. Les processus de maturation des voies visuelles antérieures et des centres de contrôle de l’oculomotricité semblent jouer un rôle central dans les mécanismes de ces nystagmus. / Studying infantile nystagmus during infancy is difficult for methodological reasons. Most such studies have been performed in adults and a posteriori. These studies in adults allowed for an improvement in the existing classifications, with now robust knowledge about the two most frequent varieties of infantile nystagmus: infantile nystagmus syndrome and fusion maldevelopment nystagmus syndrome. The characteristics and pathophysiology of nystagmus in infants–notably varieties of nystagmus with a vertical component and transitory nystagmus– need further study. For this reason: 1. We developed new techniques for the recording of eye movements in infants in the setting of a clinic. They include new stimuli, the use of specially-designed infrared photo-oculography eyetrackers and new statistical analysis paradigms. We assessed these techniques in a population of 28 infants with a nystagmus. 2. We systematically studied 32 cases of spasmus nutans, classically considered an idiopathic entity, with comprehensive clinical examination, brain imaging, electrophysiology, nystagmus recording. In 53.1% of cases, it led to the diagnosis of another condition: a neurological disease (34.3%), including cases of chiasmal gliomas (21.9%), or a retinal dysfunction (12.5%). Anterior visual pathway dysfunction is likely involved in the pathophysiology of spasmus nutans. 3. Eight cases of nystagmus having led to a diagnosis of optic pathway glioma (OPG) were also recorded and studied. Age at nystagmus onset was 2.5-10 months. The associated OPG always involved the chiasm, and represent a specific subpopulation of OPG. Clinically, the nystagmus was always classified as spasmus nutans type. Oculographic recordings showed frequencies of 2.7-5 Hz, sinusoidal waveforms, dissociation and a special type of disconjugacy, with a 180° horizontal phase shift and no vertical phase shift, exhibiting a “convection-like” movement pattern. Rarely and for short periods of time, the phase shift could change. These characteristics point towards oscillations in the vergence system, which could possibly result from the specific disruption of the vergence centres afferences in the brainstem, induced by the OPG during the sensitive period of visual development. 4. Five cases of upbeat nystagmus in infants with normal retinas and normal brain imaging were studied. The nystagmus mostly occurred in supine position and could be triggered by head rotations in the supine position. All resolved spontaneously. The characteristics of this nystagmus suggest an involvement of the otolithic system, with a secondary recalibration of the vestibulo-ocular pathways. In conclusion, the development of infant-friendly devices for eye-movements recording helps providing new insights on the pathophysiology of poorly described varieties of nystagmus, including nystagmus with a vertical component and transitory nystagmus. The maturation process of both the anterior visual pathways and the oculomotor pathways appears to be central in the mechanisms of these nystagmus.

Chez les plantes à fleurs, la gynodioécie -- système dans lequel coexistent des individus femelles et des individus hermaphrodites -- est le système de reproduction le plus commun après l'hermaphrodisme. La question de l'évolution et surtout du maintien de la gynodioécie et du polymorphisme génétique sous-jacent a intrigué les chercheurs depuis le 19e siecle. Aujourd'hui, les grands principes de son évolution sont posés mais beaucoup de zones d'ombres persistent. Durant ma thèse, j'ai exploré trois aspects de la gynodioécie en utilisant une approche expérimentale chez l'espèce Silene nutans et une approche théorique. Je me suis en premier lieu intéressée au déterminisme génétique de la gynodioécie grâce à la réalisation de croisements contrôlés qui m'ont permis de montrer que le déterminisme génétique du sexe était cytonucléaire, c'est à dire contrôlé par plusieurs gènes de stérilité mâle cytoplasmique (CMS) et plusieurs restaurateurs nucléaires de fertilité. En parallèle, j'ai porté une attention particulière aux plantes gynomonoïques -- celles où coexistent sur le même pied des fleurs pistillés (femelles) et des fleurs parfaites (hermaphrodites) -- fréquentes chez Silene nutans comme chez d'autres espèces gynodioïques. J'ai montré que les caractéristiques reproductrices et florales de ce troisième phénotype sexuel étaient souvent intermédiaires entre celles des femelles et des hermaphrodites mais pouvaient dépendre de la proportion de fleurs pistillées sur la plante. Par ailleurs et contrairement à ce qui avait été suggéré, la plasticité du phénotype gynomonoïque s'est révélée être relativement réduite, suggérant un déterminisme génétique dont la caractérisation est encore en cours. La troisième partie de ma thèse a été motivée par les preuves récentes d'hétéroplasmie -- coexistence de différents génomes mitochondriaux au sein d'un individu -- et de la transmission occasionnelle du génome mitochondrial par le pollen chez Silene vulgaris. J'ai montré théoriquement que la présence d'un gène de stérilité mâle cytoplasmique favorisait l'évolution de la fuite paternelle de mitochondries. J'ai également vérifié expérimentalement l'hérédité mitochondriale chez Silene nutans par le génotypage des descendances de croisements contrôlés. / In flowering plants, gynodioecy -- a system in which females and hermaphrodites coexist within populations -- is the most common sexual system after hermaphroditism. The evolution and maintenance of gynodiocy and its underlying polymorphism have puzzled evolutionary biologists since the 19th century. The main principles of its evolution are well known but some points remain vague. During my PhD, I explored three aspects of gynodioecy using an experimental approach in the species Silene nutans and a theoretical approach. First, I studied the genetic determination of gynodioecy using controlled crosses that showed that the genetic determination of sex was cytonuclear, i.e. controlled by several cytoplasmic male sterility (CMS) genes and several nuclear restorers of fertility. Second, I focused on gynomonoecious plants -- those that carry both pistillate (female) flowers and perfect (hermaphrodite) flowers -- that are frequently found in Silene nutans as in other gynodioecious species. I showed that the floral and reproductive traits of this third sex phenotype were often intermediate between those of females and hermaphrodites but varied with varying proportions of pistillate flowers on the plant. Contrary to what was previously thought, the plasticity of the gynomoneocious phenotype was found to be limited, suggesting a genetic determination whose characterization is still in progress. The third part of my PhD was motivated by recent evidences of heteroplasmy -- the coexistence of different mitochondrial genomes within an individual -- and occasional transmission of the mitochondrial genome through pollen in Silene vulgaris. I showed theoretically that the occurrence of a cytoplasmic male sterility gene can favor the evolution of paternal leakage of mitochondria. I also investigated mitochondrial inheritance in Silene nutans by genotyping progenies from controlled crosses.

Classical biocontrol systems are sometimes treated as an exercise in community assembly. As such, they include multiple species interactions. This thesis explores multi-species aspects in classical weed biocontrol, using thistles as a case study. The abundance, phenology and impact of three biocontrol agents were followed on their target host, Carduus nutans L. and are described, for the first time in New Zealand for two of them (Urophora solstitialis L. and Trichosirocalus horridus sensu (Panzer)). Composition in New Zealand of the recently revised Trichosirocalus weevil species complex was surveyed nation-wide. One species only was found, albeit exhibiting a wider host range than anticipated from the published revision. Interspecific interactions and individual and combined effect of multiple biocontrol agents on C. nutans were tested in cage setups; the effect on the weed population was then estimated by manipulations of an existing matrix population model for this weed in New Zealand. The potentially better seed predator (U. solstitialis) was outcompeted by the worse seed predator (Rhinocyllus conicus (Froehlich)) which has similar niche preference. Urophora solstitialis was also adversely impacted by the crown-root feeder (T. horridus). Trichosirocalus horridus affected C. nutans survival, even at the medium density used, and significantly reduced potential seed production by 33%; in field densities, T. horridus is likely to affect C. nutans even more. Urophora solstitialis was estimated to destroy about 28% of the remaining seed in the absence of the other agents, and about 17% in the presence of T. horridus. The estimated combined effect of T. horridus and U. solstitalis on C. nutans population growth rate was greater than the effect of either agent alone. In the face of growing weed invasions, multiple thistle species were used to test ‘multi-targeting’ as a novel approach to target groups of ‘sleeper weeds’. Both in a field experiment and in a field survey, the seed predator R. conicus was found to attack and damage some ‘non-target’ thistle species more in the presence of the target species (C. nutans) than in its absence; however, levels of attack on non-target species were always modest. The ultimate goal of biocontrol is to reduce weed populations. A field survey revealed that current population densities of multiple thistle species in Canterbury are not obviously lower than in the mid 1980s, when only R. conicus was present. This may be because successful biocontrol has reduced the management input required to maintain the same thistle density.

Classical biocontrol systems are sometimes treated as an exercise in community assembly. As such, they include multiple species interactions. This thesis explores multi-species aspects in classical weed biocontrol, using thistles as a case study. The abundance, phenology and impact of three biocontrol agents were followed on their target host, Carduus nutans L. and are described, for the first time in New Zealand for two of them (Urophora solstitialis L. and Trichosirocalus horridus sensu (Panzer)). Composition in New Zealand of the recently revised Trichosirocalus weevil species complex was surveyed nation-wide. One species only was found, albeit exhibiting a wider host range than anticipated from the published revision. Interspecific interactions and individual and combined effect of multiple biocontrol agents on C. nutans were tested in cage setups; the effect on the weed population was then estimated by manipulations of an existing matrix population model for this weed in New Zealand. The potentially better seed predator (U. solstitialis) was outcompeted by the worse seed predator (Rhinocyllus conicus (Froehlich)) which has similar niche preference. Urophora solstitialis was also adversely impacted by the crown-root feeder (T. horridus). Trichosirocalus horridus affected C. nutans survival, even at the medium density used, and significantly reduced potential seed production by 33%; in field densities, T. horridus is likely to affect C. nutans even more. Urophora solstitialis was estimated to destroy about 28% of the remaining seed in the absence of the other agents, and about 17% in the presence of T. horridus. The estimated combined effect of T. horridus and U. solstitalis on C. nutans population growth rate was greater than the effect of either agent alone. In the face of growing weed invasions, multiple thistle species were used to test ‘multi-targeting’ as a novel approach to target groups of ‘sleeper weeds’. Both in a field experiment and in a field survey, the seed predator R. conicus was found to attack and damage some ‘non-target’ thistle species more in the presence of the target species (C. nutans) than in its absence; however, levels of attack on non-target species were always modest. The ultimate goal of biocontrol is to reduce weed populations. A field survey revealed that current population densities of multiple thistle species in Canterbury are not obviously lower than in the mid 1980s, when only R. conicus was present. This may be because successful biocontrol has reduced the management input required to maintain the same thistle density.

Chez les plantes à fleurs, la gynodioécie -- système dans lequel coexistent des individus femelles et des individus hermaphrodites -- est le système de reproduction le plus commun après l'hermaphrodisme. La question de l'évolution et surtout du maintien de la gynodioécie et du polymorphisme génétique sous-jacent a intrigué les chercheurs depuis le 19e siecle. Aujourd'hui, les grands principes de son évolution sont posés mais beaucoup de zones d'ombres persistent. Durant ma thèse, j'ai exploré trois aspects de la gynodioécie en utilisant une approche expérimentale chez l'espèce Silene nutans et une approche théorique. Je me suis en premier lieu intéressée au déterminisme génétique de la gynodioécie grâce à la réalisation de croisements contrôlés qui m'ont permis de montrer que le déterminisme génétique du sexe était cytonucléaire, c'est à dire contrôlé par plusieurs gènes de stérilité mâle cytoplasmique (CMS) et plusieurs restaurateurs nucléaires de fertilité. En parallèle, j'ai porté une attention particulière aux plantes gynomonoïques -- celles où coexistent sur le même pied des fleurs pistillés (femelles) et des fleurs parfaites (hermaphrodites) -- fréquentes chez Silene nutans comme chez d'autres espèces gynodioïques. J'ai montré que les caractéristiques reproductrices et florales de ce troisième phénotype sexuel étaient souvent intermédiaires entre celles des femelles et des hermaphrodites mais pouvaient dépendre de la proportion de fleurs pistillées sur la plante. Par ailleurs et contrairement à ce qui avait été suggéré, la plasticité du phénotype gynomonoïque s'est révélée être relativement réduite, suggérant un déterminisme génétique dont la caractérisation est encore en cours. La troisième partie de ma thèse a été motivée par les preuves récentes d'hétéroplasmie -- coexistence de différents génomes mitochondriaux au sein d'un individu -- et de la transmission occasionnelle du génome mitochondrial par le pollen chez Silene vulgaris. J'ai montré théoriquement que la présence d'un gène de stérilité mâle cytoplasmique favorisait l'évolution de la fuite paternelle de mitochondries. J'ai également vérifié expérimentalement l'hérédité mitochondriale chez Silene nutans par le génotypage des descendances de croisements contrôlés.

Cyrtanthus nutans (RA Dyer) is a KwaZulu-Natal Province near-endemic species, classified as vulnerable in South Africa (IUCN Red Data categories). Literature references suggest that no recent ecological research has been conducted on Cyrtanthus nutans. Last assessed in 2007, the current study determined the demographics and the abiotic and biotic factors that influenced the distribution and range of Cyrtanthus nutans. Key determinants influencing the autecology, distribution and population dynamics of Cyrtanthus nutans were investigated. Anthropological factors influencing the decline of populations were addressed. Two investigations were undertaken for the current study on Cyrtanthus nutans in Dundee in North-western KwaZulu-Natal, South Africa namely a survey to determine the population dynamics and autecology of the species and the effect key determinants have on the recruitment and survival. Sites of occurrence and the ecological and anthropological factors that influence the existence of plants were documented. Experimental plots were conducted to determine the influence of climatological factors, fire and defoliation on the emergence and survival of Cyrtanthus nutans plants. A preference was found for soils with high nitrogen and organic carbon, low phosphorus and acidity levels situated on slopes of < 10% on mid to lower terrain slopes within an altitude range of between 1 100 and 1 300 m (a.m.s.l.) in the Sour Sandveld and Moist Tall Grassveld Bioresource Groups. The influence that climatological factors, fire and defoliation had on the emergence and seed recruitment of Cyrtanthus nutans were determined through a small plot experiment in the Dundee area. Mean relative humidity (%) and mean rainfall two weeks before emergence in conjunction with treatments were highly significant (P<0.001). Burning treatments B (fire inclusion and defoliation inclusion) and BC (fire inclusion and defoliation exclusion) were more highly significant on the emergence of Cyrtanthus nutans plants than any other treatments. ii | P a g e Increasing fragmentation of thriving populations of Cyrtanthus nutans populations is occurring through landuse change, mismanagement of veld and non-compliance of legislation. Continued monitoring and awareness is essential in the survival of this species. / Environmental Sciences / M. Sc. (Environmental Sciences)