Academic literature on the topic 'Self-incompatibility system'

Abstract Recent genetic analyses have demonstrated that self-incompatibility in flowering plants derives from the coordinated expression of a system of loci. To address the selective mechanisms through which a genetic system of this kind evolves, I present a three-locus model for the origin of gametophytic self-incompatibility. Conventional models assume that a single locus encodes all physiological effects associated with self-incompatibility and that the viability of offspring depends only on whether they were derived by selfing or outcrossing. My model explicitly represents the genetic determination of offspring viability by a locus subject to symmetrically overdominant selection. Initially, the level of expression of the proto-S locus is insufficient to induce self-incompatibility. Weak gametophytic self-incompatibility arises upon the introduction of a rare allele at an unlinked modifier locus which enhances the expression of the proto-S locus. While conventional models predict that the origin of self-incompatibility requires at least two- to threefold levels of inbreeding depression, I find that the comparatively low levels of inbreeding depression generated by a single overdominant locus can ensure the invasion of an enhancer of self-incompatibility under sufficiently high rates of receipt of self-pollen. Associations among components of the incompatibility system promote the origin of self-incompatibility. Enhancement of heterozygosity at the initially neutral proto-S locus improves offspring viability through associative overdominance. Further, the modifier that enhances the expression of self-incompatibility develops a direct association with heterozygosity at the overdominant viability locus. These results suggest that the evolutionary processes by which incompatibility systems originate may differ significantly from those associated with their breakdown. The genetic mechanism explored here may apply to the evolution of other systems that restrict reproduction, including maternal-fetal incompatibility in mammals.

Progenies derived from self-pollination and parent–offspring backcrosses of Echinacea purpurea (L.) Moench accession PI 631307 revealed that a sporophytic self-incompatibility (SI) system was operating in this germplasm. Offspring of progenies from the original accession were self-incompatible, but most self-pollinations resulted in some self-seed set. One seedling from such a self-pollination was reciprocally crosscompatible with its parent, proving that a sporophytic SI system was operational. The F3BC1 progeny could be classified into two offspring groups. The first group of two seedlings was reciprocally compatible with its seed parent but reciprocally incompatible with its pollen parent based on stigma collapse of the seed parent florets 2 to 4 days after pollination. The second offspring group of three seedlings was reciprocally incompatible with its seed parent but reciprocally compatible with its pollen parent. Seed set data were in agreement with classification by stigma collapse in seven of 10 backcrosses, including in several reciprocally compatible backcrosses that provided further proof of a sporophytic SI system. Additionally, a χ2 test showed that the data fit a sporophytic SI model with S allele dominance operating in pollen and pistil. Assuming that S allele dominance is widespread within Echinacea purpurea, it should be possible to produce inbred lines by making successive generations of full-sib crosses.

Self–incompatibility (SI) involves the recognition and rejection of self or genetically identical pollen. Gametophytic SI is probably the most widespread of the SI systems and, so far, two completely different SI mechanisms, which appear to have evolved separately, have been identified. One mechanism is the RNase system, which is found in the Solanaceae, Rosaceae and Scrophulariaceae. The other is a complex system, so far found only in the Papaveraceae, which involves the triggering of signal transduction cascade(s) that result in rapid pollen tube inhibition and cell death. Here, we present an overview of what is currently known about the mechanisms involved in controlling pollen tube inhibition in these two systems.

Abstract Analysis of nucleotide sequences that regulate the expression of self-incompatibility in flowering plants affords a direct means of examining classical hypotheses for the origin and evolution of this major feature of mating systems. Departing from the classical view of monophyly of all forms of self-incompatibility, the current paradigm for the origin of self-incompatibility postulates multiple episodes of recruitment and modification of preexisting genes. In Brassica, the S locus, which regulates sporophytic self-incompatibility, shows homology to a multigene family present both in self-compatible congeners and in groups for which this form of self-incompatibility is atypical. A phylogenetic analysis of S-allele sequences together with homologous sequences that do not cosegregate with self-incompatibility permits dating the change of function that marked the origin of self-incompatibility. A generalized least-squares method is introduced that provides closed-form expressions for estimates and standard errors for function-specific divergence rates and times of divergence among sequences. This analysis suggests that the age of the sporophytic self-incompatibility system expressed in Brassica exceeds species divergence within the genus by four- to fivefold. The extraordinarily high levels of sequence diversity exhibited by S alleles appears to reflect their ancient derivation, with the alternative hypothesis of hypermutability rejected by the analysis.

Low seed set has been reported following self-pollinations of flowering dogwood (Cornus florida L.). The objective of this study was to verify the presence of self-incompatibility in C. florida. `Cherokee Princess' stigmas and styles were collected 1, 2, 4, 8, 12, 24, 48, and 72 hours after cross- and self-pollinations, stained with aniline blue and observed using a fluorescence microscope. Pollen germinated freely following self-pollinations, but self-pollen tubes grew slower than those resulting from cross-pollinations. By 48 hours after cross-pollination, pollen tubes had reached the bottom of the style while pollen tubes in self-pollinated flowers had only penetrated the upper third of the style. Evidence of reduced pollen tube growth rate in self-pollinations of `Cherokee Chief' and `Cherokee Brave' was also obtained. This study provides evidence of a gametophytic self-incompatibity system in C. florida. It was also determined that stigmas of C. florida `Cherokee Princess' are receptive to pollen from 1 day prior to anthesis to 1 day after anthesis.

[EN] Self-incompatibility (SI) comprises a compendium of molecular intraspecific barriers, controlled by the S-locus, which enhances outcrossing and prevents inbreeding. Solanaceae, Plantaginaceae and Rosaceae exhibit the Gametophytic SI (GSI) type where specific recognition is controlled by S-RNases and S-locus F-box (SFB) proteins as the female and male S-determinants, respectively. On the other hand, unlinked S-locus genes known as modifier factors are also completely necessary for the mechanism to function. The GSI system seems to be basically preserved in Prunus but striking differences with Solanaceae and other Rosaceae have also been observed. On the basis of this background, this thesis is focused on the identification and characterization of modifiers involved in Prunus GSI to improve our understanding of the underlying mechanism. Previous works in apricot showed that an S-locus unlinked mutation expressed in pollen and located at the distal end of chr. 3 (M-locus) confers self-compatibility in the cv. 'Canino'. In this work, another self-compatible apricot cultivar, named 'Katy', was molecular and genetically analyzed. Similarly, an S-locus unlinked pollen-part mutation was found to cause the loss of self-incompatible response. A mapping strategy based on segregation distorted loci mapped 'Katy' mutation (referred as m-mutation) at the distal end of chr. 3, in a region overlapping with that identified for 'Canino' M-locus. A new screening was carried out to identify additional self-compatible mutants in apricot cultivar/accessions from germplasm banks. Through S-genotyping, three uncategorized S-alleles were recovered and two new mutations putatively conferring self-compatibility (SC) by affecting the male S-determinant SFB were detected. Additionally, M-genotyping showed that the same mutated m-haplotype was shared by 'Canino' and 'Katy', but also by 17 cultivars more from North-America and Western-Europe. A widely distributed haplotype M1-0 was proposed as the putative m-haplotype ancestor suggesting that it arose much later in time than SC-allele, a mutation in the S-locus also conferring SC in apricot. In order to identify this mutation, an integrative genetic, genomic and transcriptomic approach based on NGS data from 'Canino', 'Katy' and the self-incompatible apricot cultivar 'Goldrich' was carried out. This approach led to identify a unique polymorphism able to explain the self-compatible phenotype, a FaSt insertion type of 358-bp in coupling with the m-haplotype within a gene encoding a disulfide bond A-like oxidoreductase (named PaMDOr). PaMDOr was found to be differentially over expressed in mature anthers and the FaSt insertion is predicted to produce a truncated protein. These two findings also support PaMDOr as the pollen-part mutated modifier conferring SC in apricot. Furthermore, phylogenetic analyses suggest PaMDOr as a putative paralog of its contiguous gene (PaM-8), that emerged after the split of the Rosaceae and Solanaceae and which function became essential for the proper functioning of the GSI system in Prunus. Aimed to shed light on the differences and similarities between the S-RNase-based GSI systems in Rosaceae and Solanaceae, orthology relationships were analyzed for modifiers. Putative orthologs were found for NaTrxh, SBP1 and MdABCF in Prunus but a more complex evolutionary pattern was detected for 120K, NaStEP and NaPCCP. Thus, in spite of the differences, it can be hypothesized that part of the GSI modifier factors are shared by both families. As a whole, the multidisciplinary strategy developed in this thesis has allowed us to identify a novel modifier factor (PaMDOr) essential for the self-incompatible response in Prunus as the most significant contribution. In addition, new sources of SC have been detected in apricot and the orthology analysis helped to deepen our understanding on evolutionary aspects of the S-RNase-based GSI system exhibited by Prunus.
[ES] La autocompatibilidad (AI) comprende un conjunto de barreras moleculares intraespecíficas, controladas por el locus S, que favorecen la polinización cruzada y previenen de la endogamia. Solanáceas, Plantagináceas y Rosáceas presentan la llamada AI gametofítica (AIG) donde el reconocimiento específico está controlado por ARNasas-S y proteínas F-box del locus S (SFB) como los determinantes femenino y masculino, respectivamente. Por otra parte, genes no ligados al locus S, conocidos como factores modificadores, son también totalmente necesarios para la correcta regulación del mecanismo. El sistema AIG parece estar básicamente conservado en Prunus pero se han observado notables diferencias con Solanáceas y otras Rosáceas. Con estos antecedentes, el trabajo realizado en esta tesis se ha centrado en la identificación y caracterización de factores modificadores de la AIG en Prunus con el fin de mejorar nuestro conocimiento del mecanismo subyacente. Trabajos previos en albaricoquero mostraron la existencia de una mutación expresada en el polen y no ligada al locus S, que se localiza en el extremo distal del cr.3 (locus M) y que es capaz de conferir autocompatibilidad (AC) en el cultivar 'Canino'. En esta tesis, otro cultivar de albaricoquero autocompatible llamado 'Katy' fue genética y molecularmente analizado. De manera parecida a 'Canino', una mutación que afectaba a un factor no ligado al locus S expresado en el polen era el causante de la pérdida de la respuesta autoincompatible. La mutación en 'Katy' se consiguió mapear en el extremo distal del cr.3 (mutación m), una región que solapa con la identificada para 'Canino'. Una búsqueda para la identificación de nuevo mutantes autocompatibles en cultivares/accesiones de albaricoquero procedentes de bancos de germoplasma fue realizado. Por medio del genotipado del locus S, 3 alelos S no clasificados con anterioridad fueron hallados, mientras que 2 nuevas mutaciones autocompatibles que parecen haber afectado al determinante S masculino SFB fueron detectadas. Adicionalmente, el genotipado para el locus M mostró que el mismo haplotipo m mutado está compartido por 'Canino' y 'Katy' y 17 cultivares más del norte de América y el oeste de Europa. El haplotipo M1-0 ha sido propuesto como posible ancestro del haplotipo m, sugiriendo que éste surgió mucho más tarde que el alelo Sc, mutación del locus S que también confiere AC en albaricoquero. Con el objetivo de identificar esta mutación, un abordaje integral tanto a nivel genético como genómico y transcriptómico mediante datos NGS procedentes de 'Canino', 'Katy' y del cultivar de albaricoquero autoincompatible 'Goldrich' fue llevado a cabo. Esta aproximación sirvió para identificar un único polimorfismo capaz de explicar el fenotipo de AC, una inserción tipo FaSt de 358 pb en acoplamiento con el haplotipo m en un gen que codifica para una disulfide bond A-like oxidoreductase (PaMDOr). PaMDOr mostró estar diferencialmente sobre-expresado en anteras maduras, mientras que la inserción FaSt predice la formación de una proteína truncada. Estos dos hechos apoyan a PaMDOr como el factor modificador de la parte del polen que confiere AC en albaricoquero. Adicionalmente, análisis filogenéticos sugieren que PaMDOr podría ser un parálogo del gen contiguo (PaM-8) que surgió después de la división de Rosáceas y Solanáceas, cuya función ha llegado a ser esencial para el correcto funcionamiento del sistema en Prunus. A fin de arrojar cierta luz en las diferencias y similitudes entre los sistemas de AIG basado en ARNasas-S de Rosáceas y Solanáceas, las relaciones de ortología para factores modificadores fueron estudiadas. Ortólogos candidatos fueron encontrados para NaTrxh, SBP1 y MdABCF, sin embargo, un patrón evolutivo más complejo fue observado para NaStEP, 120K y NaPCCP. De modo que, a pesar de las diferencias, se puede hipotetizar que una parte de los modificadores de la AIG están comparti
[CAT] L'autocompatibilitat (AI) comprèn un conjunt de barreres moleculars intraespecífiques, controlades pel locus S, que afavorixen la pol·linització creuada i prevé de l'endogàmia. Solanàcies, Plantaginàcies i Rosàcies presenten l'anomenada AI gametofítica (AIG) on el reconeixement específic està controlat per ARNases-S i proteïnes F-box del locus S (SFB) com a determinants femení i masculí, respectivament. Per un altra banda, gens no lligats al locus S, coneguts com factors modificadors, són també totalment necessaris per a la correcta regulació del mecanisme. El sistema AIG pareix estar bàsicament conservat en Prunus, però s'han observat notables diferències amb Solanàcies i altres Rosàcies. Amb estos antecedents, el treball realitzat durant aquesta tesi se ha focalitzat en la identificació i caracterització de factors modificadors de l'AIG en Prunus a fi d millorar el nostre enteniment del mecanisme subjacent. Treballs previs a l'albercoquer mostraren l'existència d'una mutació expressada al pol·len no lligada al locus S, la qual està localitzada a l'extrem distal del cr.3 (locus M) i es capaç de conferir autocompatibilitat (AC) al cultivar 'Canino'. En aquest treball, un altre cultivar d'albercoquer autocompatible anomenat 'Katy' va ser genètica i molecularment analitzat. De manera pareguda a 'Canino', una mutació que afecta a un factor no lligat al locus S expressat al pol·len era la causa de la perduda de la resposta autoincompatible. La mutació a 'Katy' es va mapetjar a l'extrem distal del cr.3 (mutació m) en una regió solapant amb la identificada per a 'Canino'. Una recerca per a la identificació de nous mutants autocompatibles en cultivars i/o accessions d'albercoquer procedents de bancs de germoplasma va ser portada a terme. Mitjançant el genotipatge del locus S, 3 al·lels S no classificats amb anterioritat van ser trobats, mestres que dos noves mutacions AC que pareixen haver afectat al determinant S masculí SFB varen ser detectades. Amés, el genotipatge del locus M va mostrar que el mateix haplotip m mutat està compartit per 'Canino' i 'Katy', però també per 17 cultivars més del nord d'Amèrica i l'oest d'Europa. El haplotip M1-0, ampliamente distribuït, ha sigut proposat com a possible ancestre del haplotip m, sugerint que aquest va sorgir més tard que el al·lel Sc, una mutació al locus S que també conferix AC a l'albercoquer. Amb l'objectiu d'identificar aquesta mutació, un abordatge integral tant a nivell genètic com genòmic i transcriptòmic mitjançant diversos tipus de dades NGS provinents de 'Canino', 'Katy' i del cultivar d'albercoquer autoincompatible 'Goldrich' va ser portat terme. Aquesta aproximació va permetre identificar un únic polimorfisme capaç d'explicar el fenotip AC, es tracta d'una inserció de 358 pb en adaptament amb el haplotip m en un gen que codifica per a disulfide bond A-like oxidoreductase (PaMDOr). PaMDOr va mostrar estar diferencialment sobre-expressat en anteres madures, mentres que la inserció FaSt prediu la formació d'una proteïna truncada. Estos dos fets recolzen a PaMDOr com al factor modificador de la part del pol·len que conferix AC en albercoquer. A més a més, anàlisis filogenètics suggerixen que PaMDOr podria ser un paràlog del seu gen contigu (anomenat PaM-8) que va sorgir després de la divisió de Rosàcies i Solanàcies, en la qual la funció ha arribat a ser fonamental per al correcte funcionament del sistema d'AIG a Prunus. A fi de tirar certa llum en quant a les diferències i similituds entre els sistemes d'AIG basats en ARNases-S de Rosàcies i Solanàcies, les relacions d'ortologia per als factors modificadors va ser estudiat. Ortòlogs candidat van ser trobats per a NaTrxh, SBP1 i MdABCF, no obstant, un patró evolutiu més complex va ser observat per a NaSTeP, 120K i NaPCCP. De tal manera que, a pesar de les diferències, es pot plantejar la hipòtesi de que una part dels modificadors de l'AIG estan
Muñoz Sanz, JV. (2016). Crossability barriers in Prunus: the role of modifiers in the regulation of the gametophytic self-incompatibility system [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68489
TESIS

Mestrado em Biologia Molecular e Celular
To understand the molecular basis of the S-RNase-based gametophytic selfincompability system of subtribe Pyrinae from Rosaceae family, in this work, Malus x domestica species was used to determine the genes involved in pollen S-specificity. Previously 18 F-box genes, similar to the S-locus F-box brothers (SFBBs), were identified by conventional polymerase chain reaction techniques and with the pollen transcriptome analysis of nine M. domestica cultivars. However, not all 10 S-haplotypes, covered by the nine M. domestica cultivars used, have been characterized for all SFBB genes, and 12 SFBB sequences found, align as highly divergent sequences in 12 SFBB genes. Thus, in this work, by cloning and sequencing analysis of two highly diverged alleles, namely, SFBBGu8 and SFBBN3 of SFBB5 and SFBB1 genes, respectively, was concluded that SFBBGu8 sequence represent the S1- and S24- diverged alleles of SFBB5 gene, while SFBBN3 sequence represent the S28- diverged allele of SFBB1 gene. Additionally, for SFBB5 gene there is no SFBB copy number variation. This pattern was also observed for other 12 SFBB genes. For 15 of the 18 SFBB genes identified, linkage with the S-RNase gene (gene involved in pistil S-specificity) was established by segregation analysis of the F1 progeny from the cross of Fuji (S1, S9) with Honeycrisp (S2, S24), previously genotyped. As result, for SFBB2, SFBB3, SFBB4, SFBB6, SFBB7, SFBB8, SFBB9, SFBB10, SFBB11, SFBB12, SFBB13, SFBB14 and SFBB16 genes, linkage with at least one S-RNase allele was established. Thus, since these 13 SFBB genes also present pollen-specific expression and S-haplotypespecific polymorphism, these genes are pollen S-genes. In conclusion, consistent features with the collaborative non-self recognition model, were identified in M. domestica species, such as, large number of SFBB genes and the presence of highly diverged SFBB alleles, that may be conserved in other S-haplotypes, and thus, involved in the recognition of a particular non-self S-RNase. However, in M. domestica species, it was not verified SFBB copy number variation within the different S-haplotypes, as observed in Petunia. The characterization of the S-pollen genes involved in the self-incompatibility mechanism in M. domestica species is the first step to characterize self-pollen rejection mechanism in Pyrinae subtribe.
Para compreender a base molecular do sistema de auto-incompatibilidade gametofítica baseada em S-RNases da subtribo Pyrinae da família Rosaceae, neste trabalho, a espécie Malus x domestica foi utilizada para determinar os genes envolvidos na especificidade S do pólen. Previamente 18 genes F-box, semelhantes aos “S-locus F-box brothers” (SFBBs), foram identificados por uma abordagem baseada em técnicas convencionais de reação em cadeia da polimerase e por análise de transcriptomas do pólen de nove cultivares de M. domestica. Contudo, nem todos os 10 haplótipos S, cobertos pelos nove cultivares de M. domestica utilizados, foram caracterizados para todos os genes SFBB, e 12 sequências SFBB encontradas, alinham como sequências altamente divergentes em 12 genes SFBB. Assim, neste trabalho, por clonagem e sequenciação de dois alelos altamente divergentes, nomeadamente, SFBBGu8 e SFBBN3 dos genes SFBB5 e SFBB1, respectivamente, concluiu-se que a sequência SFBBGu8 representa os alelos divergentes S1- e S24- do gene SFBB5, enquanto que a sequência SFBBN3 representa o alelo divergente S28- do gene SFBB1. Adicionalmente, para o gene SFBB5 não existe variação do número de cópias dos SFBBs. Este padrão foi também observado para outros 12 genes SFBB. Para 15 dos 18 genes SFBB identificados, foi determinada associação com o gene da SRNase (gene envolvido na especificidade S do pistilo) através de análises de segregação da progenia F1 resultante do cruzamento de Fuji (S1, S9) com Honeycrisp (S2, S24), previamente genotipada. Como resultado, para os genes SFBB2, SFBB3, SFBB4, SFBB6, SFBB7, SFBB8, SFBB9, SFBB10, SFBB11, SFBB12, SFBB13, SFBB14 e SFBB16, foi estabelecida associação com pelo menos um alelo da S-RNase. Assim, dado que estes 13 genes SFBB também apresentam expressão exclusiva no pólen e polimorfismo específico para cada haplótipo S, estes genes são genes S do pólen. Em conclusão, foram identificadas características consistentes com o modelo “collaborative non-self-recognition” em M. domestica, tais como, um grande número de genes SFBB e a presença de alelos SFBB altamente divergentes, que podem ser conservados noutros haplótipos S e assim, estar envolvidos no reconhecimento de uma S-RNase não-própria. Contudo, em M. domestica, não ser verificou variação do número de cópias dos SFBBs nos diferentes haplótipos S, como observado em Petunia. A caraterização dos genes S do pólen envolvidos no mecanismo de auto-incompatibilidade em M. domestica é o primeiro passo para caracterizar o mecanismo de rejeição do pólen do próprio, na subtribo Pyrinae.

Dans un contexte de succès de colonisation des espèces invasives, la compréhension d’un front d’invasion est essentielle afin d’identifier des leviers de gestion. En France, Ludwigia grandiflora subsp hexapetala a envahi la plupart de réseaux hydrographiques avec des populations fertiles et stériles. Les objectifs de cette thèse étaient l’identification des facteurs influençant sa reproduction sexuée et la caractérisation de sa diversité génétique afin d’inférer le mode de reproduction efficace et de comprendre l’histoire du front d’invasion. La biologie florale et la fructification des populations fertiles et stériles dans différentes conditions climatiques et après différents croisements contrôlés ainsi que la diversité génétique des populations via un set de marqueurs moléculaires SNP ont été évaluées,Ces travaux ont montré que la reproduction sexuée de Ludwigia grandiflora subsp hexapetala est sous contrôle d’un système d’auto-incompatibilité hétéromorphique « à action tardive » de type distyle-homostyle. Nous avons identifié deux fronts d’invasion avec deux points de rencontre. Le système de reproduction efficace majoritaire est la clonalité avec un signal d’allogamie au niveau des 2 « hot-spot » de diversité, suggérant une priorisation de gestion à leurs niveaux. Ces études pourront être étendues à d’autres fronts d’invasion en Europe et aux USA
In a context of successful colonization of invasive species, understanding of an invasion front is essential in order to identify management levers. In France, Ludwigia grandiflora subsp hexapetala has invaded most river systems with fertile and sterile populations. The objectives of this thesis were the identification of factors influencing its sexual reproduction and the characterisation of its genetic diversity in order to infer the efficient mode of reproduction and to understand the history of the invasion front.Floral biology and fructification of fertile and sterile populations in different climatic conditions and after different controlled crosses as well as the genetic diversity of the populations via a set of SNP molecular markers were evaluated. These studied showed that the sexual reproduction of Ludwigia grandiflora subsp hexapetala is under the control of a "late-acting" heteromorphic self-incompatibility system of the distyle-homostyle type. We have identified two invasion fronts with two meeting points. The majority efficient breeding system is clonality with an allogamy signal at the level of the 2 diversity hot spots, suggesting management prioritization at their levels. These studies could be extended to other invasion fronts in Europe and the USA

Depuis les années 1950, l'intensification des pratiques agricoles concourt à une augmentation de la pression anthropique entraînant une raréfaction des espèces spécialistes des parcelles cultivées, ce qui contribue à l'érosion de la diversité biologique des agroécosystèmes. Parmi les espèces en déclin, on compte de nombreuses messicoles dont le bleuet (Centaurea cyanus L.), fleur emblématique des moissons. Or, cette espèce peut rendre des services écosystémiques comme hôte de prédateurs de ravageurs des cultures et ressource privilégiée de certains pollinisateurs qui justifieraient son maintien dans les champs. Nous étudions ici des facteurs biologiques qui pourraient potentiellement contribuer à son déclin : distribution spatiale, potentialité de croissance, diversité génétique des populations, survie des semences, système de reproduction. Nous avons montré, par deux campagnes de relevés, que C. cyanus n'est pas une espèce indicatrice de diversité floristique dans la parcelle cultivée. Toutefois, lorsque que le bleuet est rare dans une région, il est associé à d'autres messicoles peu fréquentes. Par contre, s'il est commun, il est associé aux zones ayant la plus forte diversité végétale. Une expérience de semis dans différents compartiments de l'agrosystème, en absence de traitements herbicides, a mis en évidence que la potentialité de croissance des bleuets est plus élevée dans le plein champ du blé que dans la moutarde et les interfaces blé/bordure. Cette croissance est limitée de manière variable par les communautés adventices présentes dans les compartiments hors champs (bordures). L'analyse de la diversité génétique à l'aide de marqueurs microsatellites de bleuets dans une petite zone agricole montre que les populations sont connectées par des flux de gènes importants. Les barrières écologiques telles que les chemins, semblent être des facteurs de structuration plus importants que la distance géographique séparant les populations. La répartition du bleuet dans le paysage agricole n'est donc pas aléatoire et apparaît dépendante de la fréquence de l'espèce dans la région ainsi que des différents éléments du paysage. Les caractéristiques du cycle biologique du bleuet ont été étudiées grâce à des expériences au champ et en serre. Nous avons montré que la longévité des akènes enfouis dans le sol chute rapidement après deux ans. Le cycle saisonnier de la dormance permet deux cohortes de levées (automne et printemps). L'étude du système de reproduction a permis de mettre en évidence que les pollinisateurs sont nécessaires pour la fécondation et que les populations sont majoritairement auto-incompatibles. Il existe cependant des individus pseudo auto-incompatibles mais leur fréquence n'est pas liée à la taille des populations ou à leur niveau d'isolement spatial. Par ailleurs, dès que le coefficient de consanguinité augmente dans les populations, la valeur phénotypique des individus baisse. La dépression de consanguinité s'exprime alors principalement pendant la phase de la germination. L'ensemble de ces caractéristiques biologiques peuvent s'avérer défavorables au bleuet dans les agroécosystèmes simplifiés actuels et ont pu entraîner son déclin dans certaines régions

Flowering plants display remarkable phenotypic diversity, especially in reproductive structures, much of which is thought to be associated with pollination by animals. Pollination syndromes are collections of floral traits (e.g. flower colour, shape, odour) that are associated with a plant attracting particular functional groups of animal pollinators. We explored the extent to which traits associated with the moth pollination syndrome translated into pollination by moths in the Pacific coast dune endemic Abronia umbellata and found mixed results: in one year of study, there was no difference in seed set by day- vs. night-pollinated inflorescences, but in another year of study, night-pollinated inflorescences set significantly more seed than those pollinated during the day. We integrate this work with tests of pollen and resource limitation of seed production and with seed set surveys of natural populations to address proximate and ultimate causes of low seed set, finding low rates of pollinator visitation, high pollen limitation of seed production in all populations studied, and no evidence of endogenous resource limitation of seed production. We propose that “excess” flowers may be functionally male, serving to increase outcross siring success. The transition from self-incompatibility and obligate outcrossing to self-compatibility and predominant selfing is the most common evolutionary transition among the flowering plants and traits associated with outcrossing may become reduced across such shifts, potentially through the action of natural selection, especially if pollinators are also herbivores, or if the signals that pollinators use to locate flowers are also used by herbivores. We examined the reduction of attractive visual and olfactory floral traits in A. umbellata across a shift from outcrossing to selfing and found a reduction of all floral traits considered. We found that floral volatile emissions were reduced more strongly than flower size or floral display (number of flowers per inflorescence), but there was no evidence of an ecological cost associated with conspicuousness: we did not find reduced leaf herbivory among selfers relative to outcrossers.
Thesis (Master, Biology) -- Queen's University, 2012-08-30 19:46:23.663

abstract: Isolation-by-distance is a specific type of spatial genetic structure that arises when parent-offspring dispersal is limited. Many natural populations exhibit localized dispersal, and as a result, individuals that are geographically near each other will tend to have greater genetic similarity than individuals that are further apart. It is important to identify isolation-by-distance because it can impact the statistical analysis of population samples and it can help us better understand evolutionary dynamics. For this dissertation I investigated several aspects of isolation-by-distance. First, I looked at how the shape of the dispersal distribution affects the observed pattern of isolation-by-distance. If, as theory predicts, the shape of the distribution has little effect, then it would be more practical to model isolation-by-distance using a simple dispersal distribution rather than replicating the complexities of more realistic distributions. Therefore, I developed an efficient algorithm to simulate dispersal based on a simple triangular distribution, and using a simulation, I confirmed that the pattern of isolation-by-distance was similar to other more realistic distributions. Second, I developed a Bayesian method to quantify isolation-by-distance using genetic data by estimating Wright’s neighborhood size parameter. I analyzed the performance of this method using simulated data and a microsatellite data set from two populations of Maritime pine, and I found that the neighborhood size estimates had good coverage and low error. Finally, one of the major consequences of isolation-by-distance is an increase in inbreeding. Plants are often particularly susceptible to inbreeding, and as a result, they have evolved many inbreeding avoidance mechanisms. Using a simulation, I determined which mechanisms are more successful at preventing inbreeding associated with isolation-by-distance.
Dissertation/Thesis
Doctoral Dissertation Molecular and Cellular Biology 2015

Abstract Currently, well stimulation in North America has evolved almost entirely to slickwater fracturing with friction reducers (FRs). Some parts of North America are notorious for their poor water quality, so wells are commonly treated using high total dissolved solids (TDS)-containing flow-back or produced water. Cationic FRs are usually applied in these systems due to their tolerance to multivalent cations in such waters. Additionally, dry friction reducers have gained momentum for better economics and logistics. In this paper, a dry cationic FR is systematically studied with respect to its "on the fly" hydration capability, friction reduction, mechanical stability, compatibility with other anionic chemical additives, and thermal stability in different levels of TDS brines. The cationic FR solution was subjected to varying shearing rates to understand its hydration capability, friction reduction, and mechanical stability. Its compatibility with anionic additives, such as a scale inhibitor, was also tested in a laboratory friction loop. Thermal stability of the cationic FR solution was studied at 150°F using a viscometer and Multi-Angle Laser Light Scattering (MALLS) method to obtain molecular weight information. The charge characteristics of the cationic FR, indicative of self-degradation properties, with exposure to heat, were also studied. Potential formation damage of the FR solution was evaluated with core flow tests in the absence of oxidizing breakers. Friction reduction and hydration tests show that the FR performs well in high TDS waters, even at low temperature, reaching its peak performance rapidly. The cationic FR possesses high mechanical stability even after being exposed to high pumping rates in the friction loop. It is well known that cationic FRs are not compatible with polyanionic scale inhibitors; in this study, a compatible scale inhibitor, SI-1, is identified. Additionally, there has historically been hesitation to use such cationic materials due to concerns of formation compatibility with negatively charged source rocks or flocculation in water treatment plants. Thermal testing with cationic FRs reveals that the material degrades to anionic without the aid of any other additive, which is confirmed by the fact that addition of polycationic additive, C1, caused coacervation in the heat-treated sample. As a result, concerns over effects of rock wettability or incompatibility with water treatment additives can be alleviated. No anionic FRs undergo similar change of the ionic charge. Thermal testing with cationic FR solutions also shows a significant viscosity drop, surprisingly without pronounced molecular weight loss (via MALLS). However, core flow testing of cationic FR fluids shows good regained permeability, even without breakers, further confirming self-cleaning capability. The degradation mechanism of these FRs will be shown. The self-cleaning capability of the dry cationic FR, even at relatively low bottomhole temperature (BHT), in combination with its high salt-tolerance, makes it an excellent friction reducer for multiple applications, especially with low quality water.