No description available.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Alice A. Winn, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Jan. 18, 2005). Includes bibliographical references.

No description available.

The southeastern coastal plain of the United States is a center of endemism for plants in temperate North America and second only to California among the states. In the southeast, Florida has the largest number of these endemic plants. The largest number of these Florida endemics can be found in the fire maintained scrub and sandhill communities located on sandy ridges in Central Florida. One such endemic is Clitoria fragrans, a rare perennial herb. C. fragrans reproduces via a mixed mating system. It produces both open, chasmogamous flowers and closed, selfed, cleistogamous flowers. Little else is known about its biology. I monitored populations of C. fragrans from 2003-2005 on the Avon Park Air Force Range. I tracked plant density, finite rate of population increase, plant survivorship and reproduction relative to the time since fire and season of fire. I found that recently burned plots had a higher density of plants than those unburned for over 13 years. Unburned populations decreased in all years of the study. In all three years, the majority of flowers produced by Clitoria fragrans were cleistogamous. The production of chasmogamous flowers appears to be influenced by plant size and potentially fire. Unburned plots had less variation than recently burned plots for all independent variables.

The population dynamics of transposons in self- and cross-fertilizing plant populations are investigated both theoretically and empirically. Models were developed to evaluate the influence of host breeding system on transposon populations. Modeling results suggest that the selfing rate is likely to have important effects on the abundance and polymorphism patterns of transposable elements in plant genomes. A primary characterization of diversity and abundance of transposons in the self-pollinating species Arabidopsis thaliana was conducted using genomic sequencing data, providing strong evidence for recent element mobility. Utilizing this information, a PCR-based approach was implemented to examine transposon dynamics in populations of Arabidopsis thaliana and its outcrossing relative, Arabidopsis lyrata. The results provide evidence for the importance of purifying selection in controlling transposon abundance in outcrossing populations, but not in selfers. Differences observed between the species are consistent with the hypothesis that host breeding systems influence the selective pressure acting on transposons.

No description available.

Thesis (Ph.D.)--Ohio University, March, 2008. / Title from PDF t.p. Includes bibliographical references.

La cléistogamie est un régime de reproduction mixte particulier – contrairement aux régimes mixtes classiques où un seul morphe floral effectue l'auto- et l'allofécondation, les espèces cléistogames produisent des fleurs fermées (cléistogames, CL) qui sont obligatoirement autofécondées et des fleurs ouvertes (chasmogames) qui sont potentiellement allofécondées. D'autres particularités sont associées aux régimes cléistogames : i) les fleurs fermées ne peuvent pas exporter de pollen (pollen discounting total), résultant avec l'absence de l'avantage automatique de l'autofécondation, ii) les couts de production des deux morphes floraux ne sont pas les mêmes, iii) les différences observées entre les descendants CL et CH sont déterminée par le degré de consanguinité mais aussi par le type de fleur dont un descendant est issu. Le taux de fleurs CH d'un individu est souvent plastique, ainsi la cléistogamie peut être un moyen d'ajuster le taux d'allofécondation en fonction des conditions environnementales. Nous avons étudié une espèce annuelle cléistogame, Lamium amplexicaule, qui peut produire une génération de plantes au printemps et une à l'automne et dont le taux CH dépend de la variation des facteurs associés avec la saison. Nous avons récolté des données d'observation en population naturelle, des expériences en conditions semi-naturelles au printemps et à l'automne, effectué des analyses génotypiques avec des marqueurs microsatellites et construit un modèle théorique simple dans le but de i) étudier la variation du taux CH et son caractère plastique ; ii) estimer le taux d'allofécondation des fleurs CH et son lien avec le taux CH ; iii) tester le caractère adaptatif de la cléistogamie plastique iv) tester différents scénarios évolutifs qui pourrait expliquer le maintien de la cléistogamie plastique de L. amplexicaule. Nos résultats montrent que la cléistogamie chez L. amplexicaule est un trait plastique et adapté à la variation entre saisons et aussi que la variation du taux CH se traduit en variation du taux d'allofécondation global. Nous résultats infirment une hypothèse classique souvent utilisée pour expliquer l'évolution de la cléistogamie, à savoir que la production des deux types des fleurs en proportions variables est une adaptation à la disponibilité des ressources, et suggèrent que c'est plutôt la différence de valeur sélective entre les descendants CL et CH ou la variation de l'abondance des pollinisateurs qui expliquent mieux la plasticité adaptative de la cléistogamie chez L. amplexicaule. Dans les perspectives de ce travail, nous proposons d'approfondir les études qui explorent le lien entre l'effet des forces évolutives qui opèrent au sein des régimes mixtes classiques (un seul morphe floral) et l'effet de la spécialisation des structures florales pour différents modes de reproduction. / Cleistogamy differs from classical mixed mating systems, for which species with single floral morph self-fertilize at intermediate rates: cleistogamous plants produce both closed cleistogamous flowers (CL) that are obligately selfed and open chasmogamous flowers (CH) that are potentially outcrossed. Because CL flowers cannot export pollen (total pollen discounting), cleistogamous species do not benefit from the automatic advantage of selfing. Furthermore, costs for producing the two floral types are different, and the two types of progeny they produce (CL and CH) have different properties that go beyond the differences between selfed and outcrossed progeny. The proportion of individual CH flowers is often plastic, suggesting this trait is an adaptation of the outcrossing rate to environmental variation. Here, we studied an annual cleistogamous species, Lamium amplexicaule, that has both spring and autumn generations each year, and whose CH proportion correlates with variation in seasonal cues. We combined data from field surveys, semi-natural experimental studies in spring and autumn, genetic analyses of neutral markers, and some theoretical modeling to i) assess the variation in CH proportion and its plasticity, ii) assess the outcrossing rate of CH flowers and its relation to the CH proportion, iii) test the adaptive character of plastic cleistogamy, and iv) test evolutionary scenarios that could explain the maintenance of plastic cleistogamy in L. amplexicaule. We show that cleistogamy in L. amplexicaule is plastic and adaptive to seasonal variation, and that CH proportion variation translates into variation of the overall outcrossing rate. Classical explanations for cleistogamy evolution relying on resource allocation to CL and CH flowers do not fit our data; we instead propose that the adaptive character of plastic cleistogamy could be due to environmentally dependent variation in fitness of CL and CH progeny and pollinator abundance. More studies of the evolution of cleistogamy need to account for the combined effect of classical evolutionary forces that operate on the reproductive systems of monomorphic flower species and the effect of floral specialization to different mating types.

<p> </p> <p>The degree of self-fertilization in a population determines levels of genetic variation and high selfing rates could thus limit future adaptive potential. Theory predicts that intermediate selfing rates should not persist, yet many plants exhibit mixed mating. Cleistogamy is a floral heteromorphism where individuals produce both showy potentially outcrossing chasmogamous flowers and closed obligately selfing cleistogamous flowers. Reproduction via cleistogamous flowers is thought to be beneficial because of their greater energetic economy compared to chasmogamous flowers but can be costly if selfing leads to inbreeding depression or accelerates the fixation of deleterious mutations within populations. Cleistogamy has evolved independently multiple times and can be used to study the maintenance of adaptive mixed mating. To investigate this, I estimated the costs and benefits of selfing in three populations of <em>Ruellia humilis </em>Nutt (Acanthaceae) in greenhouse common garden experiments. To quantify the costs, I performed hand pollinations and quantified fitness components of progeny resulting from selfing and outcrossing within- and between-populations. To quantify the relative energetic advantage of cleistogamous flowers, I measured dry flower mass, fertility, seed number per fruit, and pollen-ovule ratios of both types of flowers. I found negative cumulative inbreeding depression in all populations, indicative of selfed progeny outperforming outcrossed progeny. While the fitness consequences of between population outcrossing ranged from heterosis to outbreeding depression. When looking at the energetic benefits of selfing, I found that the cost of reproduction via cleistogamous flowers was between 3 and 14-fold less than the cost for outcrossing flowers. Finally, I combined data on inbreeding depression and the energetic costs of reproduction and found that chasmogamous flowers of <em>R. humilis </em>must provide between a 3 to a 45-fold fitness advantage to be maintained, the magnitude of which was dependent upon maternal population. Overall, I conclude that none of the existing hypotheses are sufficient enough to provide the selective advantage needed to explain the persistence of chasmogamous flowers in <em>R. humilis</em>. Without any supported explanations for the maintenance of mixed mating, the exploration of genetic constraints on the loss of chasmogamous flowers could solve this long-standing mystery. </p>

Seed heteromorphism related to chasmogamous (CH) and cleistogamous (CL) seeds can have different ecological significance in species with different functional characteristics, competitive ability and palatability. Punagrass [<i>Achnatherum brachychaetum </i> (Godr.) Barkworth], an invasive, perennial grass is common in grasslands of Argentina and it is an aggressive weed in other parts of the world. <i>Flechilla grande</i> [<i>Nassella clarazii</i> (Ball) Barkworth] is a palatable perennial grass associated with the dominant "climax" vegetation in grasslands of Argentina. Seeds of the two grasses were collected from grasslands of Argentina, and growth chamber and greenhouse experiments were conducted to determine: 1) germination, dormancy breaking, and mass of CH and CL seeds of the two species 2) effects of contrasting range condition on germination and seed mass of punagrass, 3) the relative fitness of plants from CH and CL seeds, 4) if contrasting range condition affect fitness of CH plants of punagrass, and 5) the effect of maternal nutrient environments on CH and CL seeds and on fitness in the two species. Small CH seeds of high dispersal potential were less dormant than large CL seeds of low dispersal potential in punagrass. CH and CL seeds of flechilla grande had similar mass, germination, and response to dehulling. CL seed size and CL seed production of punagrass increased with good range condition. Increasing the maternal, nutrient environment enhanced germination of CH seeds, CL seed size, growth rate, development, biomass and seed production more in punagrass than flechilla grande. Under low nutrient conditions, flechilla grande produced a few large CH seeds. CH progeny of punagrass grew fast and developed rapidly as compared to CL progeny, which in turn produced many CH seeds. CH and CL seeds of flechilla grande had similar contribution to the fitness of adult plants. In both species, the ecological significance of having seed heteromorphism is that sibling competition is probably reduced by having more diverse offspring. Heavy grazing of competitive species such as flechilla grande may favours species as punagrass with many small CH seeds, high potential for colonization as well as large CL seeds for persistence in the seed bank and seedling competition.