Les interactions entre organismes ont des conséquences majeures sur la composition des communautés et le fonctionnement des écosystèmes. En écologie l'étude des interactions négatives, telles que la prédation et la compétition, a largement dominé la littérature. Des travaux récents ont souligné l’importance des interactions positives dans la nature, telles que la facilitation, mais ces interactions restent malgré tout peu intégrées dans les théories contemporaines en écologie. Cette thèse s’inscrit dans cette démarche et aborde deux questions centrales : (i) Comment la facilitation indirecte (via la protection contre le pâturage) affecte-t-elle la structure fonctionnelle (caractéristiques des distributions de traits) des communautés de plantes ? (ii) L'effet net des interactions facilitatrice-bénéficiaire identifiées à l’échelle d’une paire d’espèces restent-elles valides en présence d’une communauté entière d'espèces bénéficiaires potentielles ? Deux expérimentations in situ dans des environnements contrastés ont été mises en place : l’exclusion du pâturage dans des tourbières tropicales alpines et une transplantation de communautés de plantules sous des plantes adultes en milieu méditerranéen semi-aride. Nous avons montré que la facilitation indirecte affectait les caractéristiques du filtre environnemental, la dominance des espèces et la différenciation de niche au sein de la communauté. Nos travaux suggèrent également que la composition des communautés de plantules modifie les interactions adultes-plantules, remettant ainsi en cause la possibilité d’extrapolation des résultats entre paires d'individus à l’échelle de la communauté. / Interactions between organisms are key drivers of community composition and ecosystem functioning. Ecology has a long history of studies on negative interactions, such as predation and competition. Recent studies have highlighted the importance of positive interactions, such as facilitation in nature. The integration of these interactions into modern ecological theory has nonetheless lagged behind. This thesis aims at contributing to this research effort and addresses two core questions : (i) How does indirect facilitation (through protection against grazing) affect the functional structure (characteristics of trait distributions) of plant communities? (ii) Does the net effect of the interactions between a species pair (benefactor-beneficiary) remain valid in the presence of several beneficiary species at community level? We set up two insitu experiments in contrasted environments: a grazing exclusion experiment in tropical alpine peatlands and a transplantation experiment of sapling communities beneath adult plants in a mediterranean environment. Our results showed that indirect facilitation affects the characteristics of the environmental filter, species dominance and niche differentiation in the community. Our results also suggested that the composition of sapling communities modifies adult-sapling interactions, thereby questioning the possibility of extrapolating results from pairs of individuals to the community scale.

A subtribo Lychnophorinae ocorre na região do Cerrado do Brasil e contém cerca de 120 espécies. Recentemente, a filogenia da subtribo Lychnophorinae, baseada em sequências de DNA e dados morfológicos foi capaz de fornecer novas informações sobre a subtribo e seus gêneros. Além disso, o Cerrado brasileiro possivelmente abriga uma parcela considerável da entomofauna neotropical. Os objetivos gerais deste projeto de pesquisa são obter perfis metabólicos de plantas da subtribo Lychnophorinae e utilizá-los como ferramenta quimiotaxonômica para auxiliar na resolução da classificação taxonômica dessa subtribo e ainda, obter perfis metabólicos de insetos que se alimentem dessas plantas, visando a identificação de possíveis interações inseto-planta. Foram analisadas 78 espécies de plantas por GC-MS e UHPLC-UV(DAD)-MS(ESI-Orbitrap) nos modos positivo e negativo de ionização. As coletas de insetos foram feitas em intervalos trimestrais e, em seguida, esses insetos foram analisados utilizando a mesma metodologia analítica das plantas. As \"impressões digitais\" metabólicas das plantas e dos insetos foram precessadas no MetAlignTM e no MSClust, e as matrizes geradas foram submetidas a análises multivariadas no SIMCA. As plantas foram submetidas a análise de componentes principais (PCA), análise de cluster hierárquico (HCA) e análise discriminante ortogonal por mínimos quadrados parciais (OPLS-DA), entretanto os insetos, juntamente com suas plantas hospedeiras, foram analisados por PCA com o intuito de determinar a correlação entre seus metabólitos secundários. Os resultados das análises metabolômicas apresentaram proximidade com a filogenia principalmente para os dois maiors gêneros, Eremanthus e Lychnophora, analisados separadamente. Portanto, os resultados sugerem que os dados gerados a partir das análises metabolômicas podem ser utilizados em estudos quimiotaxonômicos da subtribo Lychnophorinae, sobretudo como dados primários para a reconstrução filogenética de gêneros. No que diz respeito às análises de possíveis interações inseto-planta, foi possível observar que alguns espécimens apresentaram correlação significativa com as plantas hospedeiras, evidenciando que a abordagem metabolômica pode ser utilizada como ferramenta na investigação de interações inseto-planta. Nestas amostras, pôde-se observar a presença de triterpenos, flavonoides e lactonas sesquiterpênicas adquiridas nas plantas por meio da herbivoria. / The subtribe Lychnophorinae occurs in the Cerrado domain of the Brazilian Central Plateau. The relationships among its recognized genera, as well as the relationships between Lychnophorinae and other subtribes belonging in tribe Vernonieae have been recently investigated upon a phylogeny based on molecular and morphological data. In addition, a preliminar overview of insect diversity in Brazilian Cerrado suggests that it may harbor a considerable fraction of the neotropical. We here report the use of a comprehensive untargeted metabolomics approach, combining LC-MS and GC-MS data together, followed by multivariate analyses aiming to assess the congruence between metabolomics data and the phylogenetic hypothesis, as well as its potential as a chemotaxonomic tool. Also we report the use of untargeted metabolomics approach aiming to assess insect-plant interactions. We analyzed 78 species by GC-MS and LC-MS in both positive and negative ionization modes. The metabolic profiles obtained for these species were treated in MetAlign and in MSClust and the matrices generated were combined and used in SIMCA for hierarchical cluster analyses (HCA), principal component analyses (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). The insects were collected quarterly and analyzed by the same analytical methods as plants. Results show that metabolomics analyses are mostly congruent with the phylogenetic hypothesis especially at lower taxonomic levels. Therefore, our results suggest that data generated by metabolomics approaches provide valuable evidence for chemotaxonomical studies of Lychnophorinae subtribe, in particular as primary data for phylogenetic reconstruction of lineages as genera. Regarding to insects, it was possible to observe significative correlations between some insects and their host plants. In these samples, were able to identify triterpenes, flavonoids and sesquiterpene lactones.

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is an important pest of brassicaceous oilseed crops, especially canola (Brassica napus L. and Brassica rapa L.) in North America and Europe. Application of foliar insecticide is the only method currently employed to control C. obstrictus populations; because this approach is environmentally unsustainable, alternatives including host plant resistance have been explored. White mustard, Sinapis alba L., is resistant to C. obstrictus and was chosen as a potential source of resistance for B. napus oilseed. Interspecific crosses of S. alba x B. napus have produced several lines that are resistant to C. obstrictus feeding and oviposition and yield fewer, lighter-weight weevil larvae that take longer to develop. I investigated potential mechanisms of this resistance, including assessing differences in visual and olfactory cues among resistant and susceptible genotypes, and antixenosis and antibiosis. Determining effects of visual cues associated with host plant resistance required investigation of weevil vision. Deployment strategies for resistant germplasm were assessed to evaluate incorporation of susceptible refugia to promote long-term durability of resistance traits. Results reported in Chapter 2 indicate that the C. obstrictus visual system is apparently trichromatic and incorporates receptors with response maxima near 350, 450, and 550 nm. Modelling indicated that UV light alone reduced weevil responses but the interaction of yellow and UV light increased responses at a threshold reflectance level of UV. Results reported in Chapter 3 indicated that differences in yellow and UV reflectance among host plant flowers influence host selection in C. obstrictus. Results described in Chapter 4 determine differential attraction to the odours of S. alba and B. napus and among resistant and susceptible accessions. Inferences of the identities of glucosinolates found in varying amounts among susceptible and resistant genotypes suggested that 2-phenylethyl glucosinolate influenced attractiveness. Results described in Chapter 5 indicate differences in adult feeding and oviposition preferences among resistant and susceptible genotypes. Oocyte development, larval biomass and larval development time varied among weevils feeding on resistant and susceptible genotypes. Based on results of Chapter 4, 1-methoxy-3-indolylmethyl glucosinolate was implicated as contributing to antixenosis and antibiosis resistance. Results reported in Chapter 6 describe effects of mixed plots of resistant and susceptible genotypes on weevil spatial distribution and oviposition. These results are consistent with associational resistance and attributed to reduced apparency of susceptible plants in mixtures and antixenosis resistance associated with resistant germplasm. / Plant Science

The object of this thesis was to study plant community structure, especially in relation to vertebrate herbivory, in an altitudinal gradient in the Fennoscandian mountain chain. A sowing experiment in a high alpine Ranunculus glacialis population showed that seeds germinated better in cleared microsites than under established individuals. This is contrasted with a hypothesis that predicts positive plant-plant interactions in high alpine environments. It was concluded that plant-plant interactions in die studied population varied from neutral to negative, whereas no indications for positive interactions were found. An exclosure experiment in a snow-bed showed that a lemming population consumed 33 % of the available graminoids and 66 % of the mosses from August to June during a population peak. The results shows that grazing needs to be considered as a structuring factor in snow-bed vegetation. The vegetation in exclosures in another snow-bed changed from a graminoid-dominated to a herb-dominated plant community during a long-term (six years) experiment No changes of the same magnitude were seen in a tall herb meadow on a lower altitude. Survival of transplanted adult shoots from the tall herb meadow was equally high in the snow-bed as on the meadow, and germination was also high on bare ground in the snow-bed. Grazing seemed to be a more important structuring factor in the snow-bed than in the more productive tall herb meadow. Raising the grazing pressure during one growing season by introducing microtine rodents into enclosures did not cause any large short-term effects on plant community structure in a tall hob meadow or in a snow-bed. Marked shoots showed that some preferred plant species had a high shoot mortality, but biomass for pooled categories of plants was not significantly affected. It was predicted that the tall herb meadow would be more grazing sensitive than die snow-bed, but productivity on the meadow seemed to be sufficiently high for the plants to compensate for the grazing during the growing season. A greenhouse experiment showed that voles, when grazing freely, have the potential to deplete productive field layer vegetation contrary to predictions from plant defence theories. A nitrogen-based defence did not prevent heavy shoot mortality for toxic tall herbs. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 5 uppsatser.</p> / digitalisering@umu.se

No description available.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Herbivory often influences the fitness and development of attacked trees, acting as an important factor of evolutionary pressure on a species ecology. However, there are few studies that show the effects of insect herbivores on Cerrado tree species. In this study I evaluated the impact of the leaf-cutter ant Atta laevigata on the vegetative and reproductive phenology, survival, growth, architecture and leaf nutrients of six tree species of a Cerrado vegetation. For three years, I visited individuals of Cardiopetalum callophylum, Coussarea hydrangeaefolia, Guapira graciliflora, Maprounea guianensis, Vochysia tucanorum and Xylopia aromatica, and determined the intensity of phenological events and leaf-cutter ant attacks. In addition, based on the recurrence frequency and intensity of ant-attacks (often 100% of leaf removal) previously observed, I created two artificial defoliation experimental treatments that simulated high and low Atta laevigata s attack frequency. I then evaluated how the different frequencies of high intensity attacks influenced the survival, growth, flower production, leaf nutrient content and architecture of the trees. The results showed that the defoliation by leaf-cutter ants reduced the photosynthetic area of attacked trees and reduced flower and fruit production of preferred species. However, it did not affect the synchrony and timing of leaf and flower/fruit production. Herbivory frequency had a negative effect on the plant tolerance to herbivory, survival, flower production and architecture in all six species. However, for some species, the leaf content of N and P were significantly higher in defoliated trees than in control trees. These results indicated that leaf-cutter ants can be considered chronic herbivores in some areas of the Cerrado, and that their continued activities can, in the long-term, affect the structure and dynamics of the vegetation. / A herbivoria influência o sucesso reprodutivo e o desenvolvimento das plantas, atuando como um importante agente de pressão evolutiva na ecologia de algumas espécies. Porém, há poucos estudos que mostram o efeito da atividade dos insetos herbívoros nas espécies arbóreas do Cerrado. Neste estudo apresento evidências dos efeitos da formigas cortadeira Atta laevigata, sobre a fenologia, sobrevivência, crescimento, arquitetura e nutrientes foliares de seis espécies arbóreas. Durante três anos acompanhei indivíduos de Cardiopetalum callophylum, Coussarea hydrangeaefolia, Guapira graciliflora, Maprounea guianensis, Vochysia tucanorum e Xylopia aromatica e determinei a intensidade de cada evento fenológico e dos ataques por saúvas. Baseado no tempo de recorrência e na intensidade dos ataques (normalmente 100% das folhas removidas) previamente observados, criei duas categorias de desfolha que simulando uma alta e uma baixa freqüência de ataque por Atta laevigata. Dessa maneira, examinei como diferentes freqüências de ataques de alta intensidade influenciaram a sobrevivência, o crescimento, a floração, o teor de nutrientes foliares e a arquitetura das plantas. Meus resultados mostraram que a desfolha por saúvas diminuiu a área fotossintética das plantas e reduziu a produção de frutos das espécies preferidas. Porém, a sincronia e a época de produção de folhas e frutos não foram afetadas. Os resultados indicam também que a freqüência de desfolhas tem um efeito negativo na capacidade de tolerância, na sobrevivência, na produção de flores, e na arquitetura das árvores. Entretanto, para algumas espécies, as concentrações foliares de N e P foram significativamente maiores em plantas cortadas do que em não-cortadas. Estes resultados indicam que as saúvas podem ser consideradas herbívoros crônicos em áreas do Cerrado e que a atividade contínua destas formigas pode, a longo prazo, afetar a estrutura e dinâmica da vegetação. / Mestre em Ecologia e Conservação de Recursos Naturais

The westernmost spur of the Tibetan Plateau stretches to Eastern Ladakh in India. It is a region which remains poorly explored because of challenging conditions and long periods of political instability. At the same time, it is one of the highest places on earth supporting angiosperm life, which goes beyond 6000 m a.s.l. here. The whole region, due its remoteness, is practically unaffected by plant invasions and direct human activities. Thus, Ladakh represents a kind of "natural experiment", providing very long gradient of elevation suitable for comparative functional ecology as well as for testing various hypotheses concerning limitations of vascular plants. Arid climate and extreme elevations are the common factors. Our team pursued the goal of systematic botanical and ecological exploration of Ladakh, started by late Leoš Klimeš. This thesis provides insight into the main vegetation types, clonality in plants, plant-plant interactions and soil phototroph communities.

Made available in DSpace on 2016-06-02T19:30:09Z (GMT). No. of bitstreams: 1 6453.pdf: 5537867 bytes, checksum: 57a708de759300745321cdff506b4e17 (MD5) Previous issue date: 2014-10-29 / Financiadora de Estudos e Projetos / In the São Paulo State predominated two large phytoecological formations: the semideciduous forests and the savanna. The extensive use of these areas mainly for cane sugar plantations and other monocultures, caused a high loss of habitats. While still play an important role in maintaining the biodiversity of the State, there is a lack of information on bird communities in this region. In this sense, we have developed a comprehensive study on the avifauna of Porto Ferreira State Park (PFSP), which protects one of the few stretches of ecological tension between semideciduous forest and savanna in São Paulo. In Chapter I, we analyze the composition and structure of PFSP&#8223;s bird community. We recorded 207 bird species in the area, between February 2011 and October 2013, including 15 threatened/near threatened species, 22 endemic to the Atlantic Forest and two endemic to savanna. We found that the PFSP has a bird richness similar to large fragments of the region, although the most sensitive species and more demanding in the resources exploitation are less abundant compared to generalist species and to the most conserved fragments of the surroundings. In Chap. II, we evaluated the interaction between frugivorous birds and PFSP&#8223;s ornithochoric plants. There was availability of attractive fruit throughout the year, with peak productivity between September and October, in line with the pre-reproductive period of birds and the arrival of migratory species. Despite the prevalence of generalist birds that disperse mainly small seeds of plants from the early succession stages, we found the PFSP has a diversified frugivorous bird-plant interaction network compared to other forest fragments of the State, due to the variety of available environments, connection with other surroundings fragments and its medium size and rounded shape, softening the matrix impact. In Chap. III, we evaluated the potential of bird perches in increasing the seed rain in an abandoned pasture within the PFSP limits. Therefore, we installed seed traps under natural perches (living trees) and artificial, noting the number of deposited seeds increased proportionally to the amount of landing perches structures. Natural perches also provided other resources for birds, such as fruits, insects and shelter, making them more attractive. We conclude that natural perches and artificial perches with more elaborate architecture showed greater efficiency in attracting seed-disperser birds and increasing the seed deposition, being the most recommended for this area recovery and for ecological restoration projects. / No interior do Estado de São Paulo predominavam duas grandes formações fitoecológicas: as Florestas Estacionais e o Cerrado. O uso extensivo dessas áreas principalmente para plantações de cana-de-açúcar e outras monoculturas, ocasionou uma elevada perda de habitats. Embora ainda desempenhe um importante papel na manutenção da biodiversidade do Estado, há carência de informações sobre a comunidades de aves dessa região. Neste sentido, desenvolvemos um estudo amplo sobre a avifauna do Parque Estadual de Porto Ferreira (PEPF), que protege um dos poucos trechos de tensão ecológica entre Floresta Estacional Semidecidual e Cerrado do interior paulista. No Capítulo I, analisamos a composição e a estrutura da comunidade de aves do PEPF. Registramos 207 espécies de aves na área, entre fevereiro de 2011 e outubro de 2013, incluindo 15 ameaçadas/quase ameaçadas de extinção, 22 endêmicas de Mata Atlântica e duas endêmicas de Cerrado. Verificamos que o PEPF apresenta riqueza avifaunística similar aos grandes fragmentos da região, embora as espécies mais sensíveis e mais exigentes na exploração de recursos sejam pouco abundantes quando comparadas às espécies generalistas e em relação aos fragmentos mais conservados do entorno. No Cap. II, avaliamos a interação entre as aves frugívoras e as plantas ornitocóricas do PEPF. Houve disponibilidade de frutos atrativos ao longo de todo o ano, com pico de produtividade entre setembro e outubro, em consonância com o período pré-reprodutivo das aves e com a chegada de espécies migratórias. Embora predominem as aves generalistas que dispersam principalmente pequenas sementes de plantas de estágios iniciais da sucessão, constatamos que o PEPF apresenta uma rede de interações ave frugívora-planta bastante diversificada em comparação com outros fragmentos florestais do Estado, em função da variedade de ambientes disponíveis, da conexão com outros fragmentos do entorno e do seu tamanho médio e formato arredondado, amenizando os impactos da matriz. No Cap. III, avaliamos o potencial de poleiros para aves no incremento da chuva de sementes em um antigo pasto abandonado, dentro dos limites do PEPF. Para tanto, instalamos coletores de sementes sob poleiros naturais (árvores vivas) e artificiais, constatando que o número de sementes depositadas aumentou proporcionalmente à quantidade de estruturas de pouso dos poleiros. Os poleiros naturais também disponibilizaram outros recursos para a avifauna, como frutos, insetos e abrigo, tornando-os mais atrativos. Concluímos que os poleiros naturais e os poleiros artificiais com arquitetura mais elaborada demonstraram maior eficiência na atração das aves dispersoras e no incremento da deposição de sementes, sendo os mais recomendados para a recuperação daquela área e para projetos de restauração ecológica.

A subtribo Lychnophorinae ocorre na região do Cerrado do Brasil e contém cerca de 120 espécies. Recentemente, a filogenia da subtribo Lychnophorinae, baseada em sequências de DNA e dados morfológicos foi capaz de fornecer novas informações sobre a subtribo e seus gêneros. Além disso, o Cerrado brasileiro possivelmente abriga uma parcela considerável da entomofauna neotropical. Os objetivos gerais deste projeto de pesquisa são obter perfis metabólicos de plantas da subtribo Lychnophorinae e utilizá-los como ferramenta quimiotaxonômica para auxiliar na resolução da classificação taxonômica dessa subtribo e ainda, obter perfis metabólicos de insetos que se alimentem dessas plantas, visando a identificação de possíveis interações inseto-planta. Foram analisadas 78 espécies de plantas por GC-MS e UHPLC-UV(DAD)-MS(ESI-Orbitrap) nos modos positivo e negativo de ionização. As coletas de insetos foram feitas em intervalos trimestrais e, em seguida, esses insetos foram analisados utilizando a mesma metodologia analítica das plantas. As \"impressões digitais\" metabólicas das plantas e dos insetos foram precessadas no MetAlignTM e no MSClust, e as matrizes geradas foram submetidas a análises multivariadas no SIMCA. As plantas foram submetidas a análise de componentes principais (PCA), análise de cluster hierárquico (HCA) e análise discriminante ortogonal por mínimos quadrados parciais (OPLS-DA), entretanto os insetos, juntamente com suas plantas hospedeiras, foram analisados por PCA com o intuito de determinar a correlação entre seus metabólitos secundários. Os resultados das análises metabolômicas apresentaram proximidade com a filogenia principalmente para os dois maiors gêneros, Eremanthus e Lychnophora, analisados separadamente. Portanto, os resultados sugerem que os dados gerados a partir das análises metabolômicas podem ser utilizados em estudos quimiotaxonômicos da subtribo Lychnophorinae, sobretudo como dados primários para a reconstrução filogenética de gêneros. No que diz respeito às análises de possíveis interações inseto-planta, foi possível observar que alguns espécimens apresentaram correlação significativa com as plantas hospedeiras, evidenciando que a abordagem metabolômica pode ser utilizada como ferramenta na investigação de interações inseto-planta. Nestas amostras, pôde-se observar a presença de triterpenos, flavonoides e lactonas sesquiterpênicas adquiridas nas plantas por meio da herbivoria. / The subtribe Lychnophorinae occurs in the Cerrado domain of the Brazilian Central Plateau. The relationships among its recognized genera, as well as the relationships between Lychnophorinae and other subtribes belonging in tribe Vernonieae have been recently investigated upon a phylogeny based on molecular and morphological data. In addition, a preliminar overview of insect diversity in Brazilian Cerrado suggests that it may harbor a considerable fraction of the neotropical. We here report the use of a comprehensive untargeted metabolomics approach, combining LC-MS and GC-MS data together, followed by multivariate analyses aiming to assess the congruence between metabolomics data and the phylogenetic hypothesis, as well as its potential as a chemotaxonomic tool. Also we report the use of untargeted metabolomics approach aiming to assess insect-plant interactions. We analyzed 78 species by GC-MS and LC-MS in both positive and negative ionization modes. The metabolic profiles obtained for these species were treated in MetAlign and in MSClust and the matrices generated were combined and used in SIMCA for hierarchical cluster analyses (HCA), principal component analyses (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). The insects were collected quarterly and analyzed by the same analytical methods as plants. Results show that metabolomics analyses are mostly congruent with the phylogenetic hypothesis especially at lower taxonomic levels. Therefore, our results suggest that data generated by metabolomics approaches provide valuable evidence for chemotaxonomical studies of Lychnophorinae subtribe, in particular as primary data for phylogenetic reconstruction of lineages as genera. Regarding to insects, it was possible to observe significative correlations between some insects and their host plants. In these samples, were able to identify triterpenes, flavonoids and sesquiterpene lactones.

Les plantes vivent en association avec une grande diversité de microorganismes qui forment son microbiota. Ce microbiote fournit des fonctions clés qui influencent tous les aspects de la vie d'une plante, de l'établissement à la croissance jusqu'à la production. Cette thèse a pour intention de déterminer les règlent d'assemblage du microbiote et ses conséquences pour le phénotypel l'adaptation et l'évolution des plantes. Pour atteindre cet objectif nous avont utilisé différentes approches expérimentales comprenant des plantes clonales comme organismes modèles ainsi que des mésocosmes prairiaux pour analyses à l'échelle des communautés. Nos résultats ont démontré i) que les Champignons Mycohiziens à Arbuscules induisent d'important es variations phénotypiques pour les traits des plantes clonales impliqués dans l'exploration de l'espace et l'exploitation des ressources. Ces changements dépendent de l'identité des symbiontes et altèrent les capacités des plantes à développer des réponses plastiques à l'hétérogénéité environnementale. ii) Les plantes ont évolué un méchanisme permettant la transmission d'une partie de leur microbiote a leur descendance, assurant la qualité de leur habitat. iii) Le contexte spécifique des communautés de plantes est un facteur majeur structurant l'assemblage du microbiota des plantes à échelle locale. L'abondance de certaines espèces de plante dans le voisinage d'une plante cible augmente ou diminue la diversité de son microbiote, déterminant in fine ses performances. De manière générale, cette thèse démontre l'importance des organismes symbiotiques dans la compréhension de l'adaptation et de l'évolution des plantes. / Plants live in association with a wide diversity of microorganisms forming the microbiota. The plant microbiota provides a variety of key functions that influence many aspects of plant's life comprising establishment, growth and reproduction. The present thesis aims at determining the assembly rules of the plant microbiota and its consequences for plant phenotype, adaptation and evolution. To fulfill this objective, we used different experimental approaches using either clonal plants as model organisms or grassland mesocosms for community-wide analyses. Our results demonstrated i) that Arbuscular Mycorrhizal Fungi induce important phenotypic variations in clonal plants traits involved in space exploration and resources exploitation. These changes depended on the identity of the symbionts and altered the plants ability to produce plastic responses to environmental heterogeneity. ii) Plants have evolved a mechanism allowing the transmission of a part of their microbiota to their progeny, ensuring thus their habitat quality. iii) The plant community context is a major factor structuring local plant microbiota assembly. Particular plant species identity in the neighborhood increase or decrease the microbiota diversity and ultimately determine the focal plant performance. This thesis overall demonstrates the importance of symbiotic microorganisms in the understanding of the plant adaptation and evolution. From the knowledges acquired we developed a novel understanding of symbiotic interactions in clonal plants by extending the holobiont theory to the meta-holobiont theory.