Emergence of the metacommunity concept has explicitly recognized the interplay of local and regional processes. The metacommunity concept has already made a substantial contribution to the better understanding of the community composition and dynamics in a regional context. However, long-term field data for testing of available metacommunity models are still scarce and the extent to which these models apply to the real world remains unknown and some of their assumptions untested. Tests conducted so far have largely sought to fit data on the entire regional set of species to one of several metacommunity models, implicitly assuming that all species, members of the metacommunity, can be modelled in the same manner (using a single model). However, species differ in their habitat use to the extent that such uniform treatment may be inappropriate. Furthermore, in testing the metacommunity models, all metacommunity studies relay on snapshots of species distribution to assess the relative importance of local and regional processes. However, snapshot patterns may be insufficient for producing a reliable picture of metacommunity dynamics and processes shaping it. I hypothesised that the relative importance of local (competition, predation or abiotic filtering or constraints) and regional (interaction of populations with landscape, migration or dispersal) processes may vary with species' traits, including habitat specialization. The perception of importance of local and regional processes in structuring community composition obtained via static approach may vary from that obtained by considering the temporal dynamics of component species. My general approach used a model system comprising natural rock pools microcosms. I have also employed experimental approach in the laboratory. I found that different metacommunity models suit for different groups of habitat specialization. I also found this to be true whether the analyses are based on snapshot data or describing temporal dynamics of species populations. These results suggest that a metacommunity system exhibits an internal differentiation of structuring processes. Specifically, from the metacommunity perspective, the dynamics of habitat specialists are best explained by a combination of species sorting and mass effects models, while that of habitat generalists is best explained by patch dynamics and neutral models. / Thesis / Doctor of Philosophy (PhD)

Biological invasions are one of the most important threats to global biodiversity and they were also found to negatively affect some bird species. Despite relatively large number of scientific studies dealing with the impacts of invasive plants on bird communities, their results are inconsistent, especially it is not clear how birds respond to increasing levels of expansion of invasive species in native species stands. Moreover, bird responses to plant invasions seem to depend on the ecological characteristics of individual bird species. This study contributes to elucidation of this problem; I investigated the impacts of black locust (Robinia pseudoacacia) invasion on bird communities in three types of forest stands with different levels of invasion: in stands containing solely the native oak (Quercus spp.), in partially invaded stands with different proportions of black locust and oak (mixed stands) and in pure black locust stands. Previous studies that examined birds in pure oak and pure black locust stands have found that they differ markedly in vegetation structure, but not in the total number of bird species. However, habitat specialists were associated with the oak stands, while generalists with the black locust stands. Therefore, I predicted that (1) the total species richness will be...

Les mécanismes à l’origine du maintien de la forte diversité locale des arbres des forêts tropicales humides constituent encore une énigme pour les scientifiques. Cette thèse a pour but d’étudier et de comprendre certains facteurs biotiques et abiotiques qui influencent l’assemblage des communautés des forêts tropicales humides d’Amazonie. A l’aide d’une approche empirique conduite dans les forêts tropicales de Guyane française et du Loreto au Pérou, de nombreuses expériences de terrain ont été mises en place dans le but d’apporter des éléments de réponse sur les mécanismes impliqués dans le maintien de la diversité des communautés d’arbres et d’insectes des forêts amazoniennes. Dans un premier temps, cette thèse permet de souligner l’importance des pressions biotiques exercées sur les communautés d’arbres. En effet, les communautés d’insectes peuvent influencer la composition des communautés d’arbres le long d’un gradient environnemental conduisant à des compromis entre la défense et la croissance. Ces compromis ou tradeoff permettent de maintenir la coexistence des espèces de forêts tropicales humides en favorisant la spécialisation des arbres à leur habitat (Chapitre 1, Annexe 3). Cependant, de nombreux facteurs peuvent engendrer des variations dans les compromis d’allocation exhibés par les plantes, ce qui peut compliquer la validité de ces résultats. Dans ce sens, nous avons souligné l’influence du rôle de la cascade trophique et l’existence chez certaines espèces d’arbres de stratégies d’évitement des insectes (Chapitre 2). Dans un second temps, nous avons montré que les filtres environnementaux et les distances géographiques favorisent un fort turnover de la composition des arthropodes des forêts tropicales (chapitre 3, Annexe 2). Les résultats de cette étude ont des implications fondamentales sur les mécanismes qui expliquent la structuration des communautés d’insectes herbivores. Nous avons souligné l’importance de l’interaction des communautés des insectes herbivores et de leurs plantes associées. De plus, des prédictions sont présentées sur le degré de spécialisation des insectes à leur plante-hôte (Annexe 3), notamment sur les implications possibles dans les compromis d’allocation chez les plantes. Finalement, des perspectives de recherche sont proposées en vue de poursuivre ces travaux de recherche, et notamment des extensions de mes expériences vers d’autres régions tropicales et tempérées et l’intégration de la phylogénie pour comprendre des mécanismes de coévolution entre communautés d’arbres et insectes. Nous proposons également une intégration des résultats de cette thèse dans les stratégies locales et régionales de conservation des forêts tropicales du bassin amazonien. / The mechanisms underlying the maintenance of local diversity of trees in tropical rainforests remain under debate. This dissertation aims to study and understand some biotic and abiotic factors that may influence both tree and insect community assembly in lowland tropical forests of Amazonia. I used an empirical approach to study communities of trees and insects in tropical forests of French Guiana and Peru, to address the extent to which insect herbivores contribute to the turnover of tree species across strong environmental gradients. In Chapter 1, I studied how herbivorous insect communities can influence the composition of tree communities along an environmental gradient by reinforcing tradeoffs between defense and growth that promote habitat specialization (Chapter 1, Appendix 3). The complicated variation in the patterns of growth and defense from this study led me to pursue further observations of an alternative plant defense strategy of time-avoidance of herbivores, which I examined in detail in Chapter 2. I found evidence for coordinated leaf production in some tree species that was consistent with the satiation of herbivores, suggesting that multiple interactions between plants and their herbivores may be responsible for patterns of habitat specialization in trees. In the second part of the dissertation, I examined insect herbivore communities in detail to test for turnover in species composition across geographic and environmental gradients. In Chapter 3, I present evidence for substantial beta-diversity in arthropod communities throughout lowland Amazonian forests. In the discussion I propose research perspectives to complete this research, including the extension of observations to compare tropical and temperate regions and the integration of molecular phylogenetics information to study coevolution of plant lineages and their insect herbivores. I conclude with suggestions for the integration of the results of this thesis in local and regional strategies for the preservation and conservation of tropical forests in the Amazon basin.

Since the beginning of the 20th century human land use changed drastically in Central Europe. These changes included: homogenization of the landscape mosaic, intensification of agriculture, urbanization and land abandonment. In turn, these changes affected bird species and perhaps most significantly manifested in population decline of open habitat birds. Therefore, it is important to investigate sites, which were not affected by the changes mentioned above, such as military training areas (MTAs) - places dedicated to training of armed forces. Previous studies have shown that MTAs seem to host remarkably high bird diversity and abundant populations of bird species of conservation concern. This may be caused by two major factors. First, closure of MTAs to all human activies besides military training spared them of the landscape changes mentioned above. Second, the military training itself produces a very heterogeneous habitat mosaic that allows coexistence of many species with different ecological requirements. To my knowledge, no study compared bird assemblages between MTAs and surrounding landscape directly. At the same time, such data are crucial to assess the value of MTAs for bird conservation reliably and, as a consequence, they enable to think more deeply about mechanism generating this value....