En marge arrière d’aire de répartition, les espèces persistent ou disparaissent en réponse aux changements climatiques et autres facteurs globaux. Les refuges climatiques ont joué un rôle majeur dans la persistance de la biodiversité au cours des périodes de transitions climatiques majeures et une compréhension mécaniste claire de leur fonctionnement est primordiale pour la conservation des populations de marge arrière. En limite géographique sud-ouest de son aire de distribution, des fragments de hêtre (Fagus sylvatica) persistent dans des micro-refuges en raison de facteurs locaux. Connue pour sa biodiversité remarquable, la vallée du Ciron offre un laboratoire naturel idéal pour l'étude des refuges climatiques et la prédiction de leur évolution dans un climat régional de plus en plus chaud et sec. Cette thèse interdisciplinaire est centrée sur l’étude des populations de hêtres et des communautés associées par des approches in situ et ex situ combinant écologie des communautés et physique de l’environnement. Nos résultats mettent en évidence une forte originalité floristique des communautés du sous-bois des populations à hêtre de marge chaude, ainsi que l’existence de variations microclimatiques à fine échelle, fonction notamment de la topographie, de la présence de la rivière et de la localisation dans le paysage. Nous montrons que la régénération du hêtre dépend du microclimat et qu’elle est modulée par des interactions allélopathiques. De plus, notre étude met en avant le rôle facilitateur de la canopée forestière ainsi que l’importance du rayonnement solaire, au moins dans des conditions où ce dernier impacte peu la disponibilité en eau. L’ensemble des résultats suggèrent la persistance probable du hêtre dans la vallée du Ciron ainsi qu’une potentialité de présence plus importante dans le Bassin aquitain. / In the margin of their distribution range, species can persist or disappear in response to climate change and global factors. Climate refugia have played a major part in the persistence of biodiversity during periods of fundamental climatic transitions, and a clear mechanistic understanding of their functioning is essential for the conservation of marginal populations. In the southwestern geographical limit, fragments of beech populations (Fagus sylvatica) persist in micro-refugia due to the importance of local factors. Known for its remarkable biodiversity, the Ciron valley provides an ideal natural laboratory for studying climate refugia and predicting their evolution in an increasingly hot and dry regional climate. This interdisciplinary thesis involves the study of beech populations and associated communities through in-situ and ex-situ approaches combining community ecology and environmental physics. Our results underline the strong floristic originality of the undergrowth communities of warm-margin beech populations, and reveal the existence of fine-scale microclimatic variations caused, in particular, by the local topography, the presence of the river, and location in the landscape. We show that beech regeneration depends on microclimate and that it is modulated by allelopathic interactions. Moreover, our research highlights the facilitating role of the forest canopy and the importance of solar radiation, in conditions where it has low impact on water availability. The overall results suggest the likely persistence of beech in the Ciron Valley and a greater potential presence of beech in the Aquitanian Basin.

In setting the AMDR for protein at 10-35% of daily energy, the Institute of Medicine acknowledged a lack of data regarding the safety of long-term intakes. The current study assessed the impact of chronic (17 months) protein consumption at the upper end of the AMDR on renal function, histology, and inflammation. Using plant and animal whole protein sources, female Sprague-Dawley rats (70 days old; n=8-11 at 4, 8, 12, or 17 mo.) were randomized to either a normal (NP; 15% of energy) or high protein (HP; 35% of energy) diet. Egg albumen and skim milk replaced carbohydrates in the HP diet. Diets were balanced for energy, fat, vitamins and minerals, and offered ad libitum. Renal function was analyzed by creatinine clearance and urinary protein levels. Glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis were assessed on kidney sections. Kidney disease progression was determined by the measurement of transforming growth factor beta-1 (TGF-β1) and renal inflammation by the measurement of chemokines monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation normal T-cell expressed and secreted (RANTES). Rats consuming the HP compared to NP diet had ~17% higher kidney weights (P<0.0001) and ~4.8 times higher proteinuria (P<0.0001). There was a trend towards higher creatinine clearance with HP (P=0.055). Consistent with this, HP compared to NP rats had ~22% larger glomeruli (P<0.0001) and ~33% more glomerulosclerosis (P=0.0003). The HP diet had no significant effect on tubulointerstitial fibrosis and renal TGF-β1 levels and did not result in higher renal levels of MCP-1 and RANTES. In fact, per mg renal protein, HP rats had ~16% lower MCP-1 (P<0.0001) and ~34% lower levels of RANTES (P<0.0001) than NP. The absence of an increase in cytokine levels may be a reflection of the moderate changes in renal pathology observed in rats offered HP diets. These data in normal female rats suggest that protein intakes at the upper end of the AMDR are detrimental to kidney health in the long-term. While modest, this may have implications for individuals whose kidney function is compromised, especially given the prevalence of those unaware of their kidney disease within North America. / October 2007

Incorporating the best findings from current, high-quality research into routine clinical practice is the basis of evidence-based care. Chapter 1: "Systematic Review and Meta-Analysis in Evidence-Based Care" is a review of the systematic review process, including meta-analysis, aimed at clinical professionals with limited statistical training. It advocates the use of the systematic review process, outlines some general techniques, and provides selected resources where individuals can acquire additional assistance. The typical steps involved include: formulating a clear research question, defining inclusion and exclusion criteria, extracting the data and assessing the study quality, summarizing and synthesizing the evidence, and then interpreting the findings. When effort is made to minimize bias and locate as many articles on a particular topic as possible, systematic reviews and meta-analyses can produce invaluable findings for evidence-based care. Chapter 2: "The Effect of Macronutrient Distribution on the Lipid Profile in Adults: A Systematic Review and Meta-Analysis" describes a systematic review and meta-analysis that examined the impact total macronutrients had on blood lipid levels. This chapter builds upon the concepts introduced in chapter one, and assesses the effect of manipulating macronutrient distribution on the lipid profile of adults, and compares these effects to recommendations regarding macronutrients, such as the Acceptable Macronutrient Distribution Ranges (AMDRs). Suggestions related to improving the quality of meta-analyses are also outlined, and supplemental analyses are provided at the end of the dissertation.

In setting the AMDR for protein at 10-35% of daily energy, the Institute of Medicine acknowledged a lack of data regarding the safety of long-term intakes. The current study assessed the impact of chronic (17 months) protein consumption at the upper end of the AMDR on renal function, histology, and inflammation. Using plant and animal whole protein sources, female Sprague-Dawley rats (70 days old; n=8-11 at 4, 8, 12, or 17 mo.) were randomized to either a normal (NP; 15% of energy) or high protein (HP; 35% of energy) diet. Egg albumen and skim milk replaced carbohydrates in the HP diet. Diets were balanced for energy, fat, vitamins and minerals, and offered ad libitum. Renal function was analyzed by creatinine clearance and urinary protein levels. Glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis were assessed on kidney sections. Kidney disease progression was determined by the measurement of transforming growth factor beta-1 (TGF-β1) and renal inflammation by the measurement of chemokines monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation normal T-cell expressed and secreted (RANTES). Rats consuming the HP compared to NP diet had ~17% higher kidney weights (P<0.0001) and ~4.8 times higher proteinuria (P<0.0001). There was a trend towards higher creatinine clearance with HP (P=0.055). Consistent with this, HP compared to NP rats had ~22% larger glomeruli (P<0.0001) and ~33% more glomerulosclerosis (P=0.0003). The HP diet had no significant effect on tubulointerstitial fibrosis and renal TGF-β1 levels and did not result in higher renal levels of MCP-1 and RANTES. In fact, per mg renal protein, HP rats had ~16% lower MCP-1 (P<0.0001) and ~34% lower levels of RANTES (P<0.0001) than NP. The absence of an increase in cytokine levels may be a reflection of the moderate changes in renal pathology observed in rats offered HP diets. These data in normal female rats suggest that protein intakes at the upper end of the AMDR are detrimental to kidney health in the long-term. While modest, this may have implications for individuals whose kidney function is compromised, especially given the prevalence of those unaware of their kidney disease within North America.

In setting the AMDR for protein at 10-35% of daily energy, the Institute of Medicine acknowledged a lack of data regarding the safety of long-term intakes. The current study assessed the impact of chronic (17 months) protein consumption at the upper end of the AMDR on renal function, histology, and inflammation. Using plant and animal whole protein sources, female Sprague-Dawley rats (70 days old; n=8-11 at 4, 8, 12, or 17 mo.) were randomized to either a normal (NP; 15% of energy) or high protein (HP; 35% of energy) diet. Egg albumen and skim milk replaced carbohydrates in the HP diet. Diets were balanced for energy, fat, vitamins and minerals, and offered ad libitum. Renal function was analyzed by creatinine clearance and urinary protein levels. Glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis were assessed on kidney sections. Kidney disease progression was determined by the measurement of transforming growth factor beta-1 (TGF-β1) and renal inflammation by the measurement of chemokines monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation normal T-cell expressed and secreted (RANTES). Rats consuming the HP compared to NP diet had ~17% higher kidney weights (P<0.0001) and ~4.8 times higher proteinuria (P<0.0001). There was a trend towards higher creatinine clearance with HP (P=0.055). Consistent with this, HP compared to NP rats had ~22% larger glomeruli (P<0.0001) and ~33% more glomerulosclerosis (P=0.0003). The HP diet had no significant effect on tubulointerstitial fibrosis and renal TGF-β1 levels and did not result in higher renal levels of MCP-1 and RANTES. In fact, per mg renal protein, HP rats had ~16% lower MCP-1 (P<0.0001) and ~34% lower levels of RANTES (P<0.0001) than NP. The absence of an increase in cytokine levels may be a reflection of the moderate changes in renal pathology observed in rats offered HP diets. These data in normal female rats suggest that protein intakes at the upper end of the AMDR are detrimental to kidney health in the long-term. While modest, this may have implications for individuals whose kidney function is compromised, especially given the prevalence of those unaware of their kidney disease within North America.

Les aires de répartition des arbres pourraient être grandement affectées par le changement climatique. Les résultats d’analyses paléogéographiques ont montré que ces dernières se sont déjà déplacées avec les variations passées du climat. Ces études ont permis de déterminer la direction et la vitesse de migration des espèces, données utilisées actuellement pour générer des prédictions sur l’évolution de l’aire de répartition des espèces forestières en réponse au réchauffement du climat. Cependant, le contexte écologique dans lequel les arbres font face à ces changements est très différent par rapport aux changements climatiques passés : l'augmentation actuelle des températures est plus rapide, les surfaces susceptibles d’être colonisées sont occupées par des écosystèmes très différents et variés (forêts, surfaces agricoles, zones urbaines). Par conséquent, les arbres pourront-ils faire face à la rapidité des changements globaux actuels ? Auront-ils la capacité de migrer pour trouver des conditions plus favorables ou pourront-ils s’adapter et survivre à de nouvelles conditions environnementales ? Dans un premier temps, l’analyse de données historiques (plans d’aménagements de l’Office Nationale des Forêts et Inventaires Forestiers Espagnols) a permis de mettre en évidence des évènements de colonisation et d’extirpation et de quantifier la vitesse de migration de populations situées au cœur ou aux marges de leur aire de répartition. Une colonisation massive de Quercus ilex dans les dunes boisées atlantiques (limite Nord d’aire de répartition) a été mise en évidence au cours des 130 dernières années, confirmant les tendances prédites par les modèles. Cependant, les vitesses de colonisation de cette espèce restent bien inférieures aux déplacements de son bioclimat estimés à partir de modèles de niche. Les espèces localisées en limite Sud d’aire de répartition présentent des remontées altitudinales plus importantes que pour celles situées au cœur de leur aire. En conclusion, nos résultats montrent que les changements globaux ont déjà impactés la répartition des arbres malgré l’existence d’un décalage temporel entre les réponses migratoires des espèces forestières et le déplacement de leur bioclimat. Le stress hydrique est le facteur prépondérant pouvant expliquer le dépérissement des arbres dans un milieu dont la disponibilité en eau est limitée, notamment en marge chaude d’aire de répartition. Nous avons, par conséquent, étudié la résistance à la sécheresse et ses mécanismes chez les plusieurs espèces d’Angiospermes. Nos résultats montrent qu’un seuil de 90% d’embolie mène à des dommages physiologiques irréversibles de la plante et à la mort par déshydratation. Ce seuil est considérablement plus élevé que celui précédemment observé chez les conifères. L’étude du fonctionnement hydraulique d’espèces de chênes co-occurrentes nous a permis de montrer que la survie de Q. robur pourrait être menacée dans les forêts atlantiques dans un contexte de sécheresses de plus en plus intenses car il y subit des taux d’embolie native élevés. Au contraire, Q. ilex présente des taux d’embolie négligeables sur ce même site d’étude.Les vitesses réelles de migrations constituent des données empiriques essentielles qui nous renseignent sur les capacités migratoires effectives des arbres. Elles pourront être intégrées dans les modèles de répartition, tout comme les seuils d’embolie induisant la mort des arbres. / Tree distribution could be highly affected by climate change. Results of paleogeographic studies showed that tree distribution ranges have already shifted with past climate changes. These data are currently used to model the evolution of species distribution in response to global warming. However, the ecological context in which species have to cope with climate change is very different than the past one: the current increase of temperature occurs faster than the past global warming, the areas being likely colonized are covered by various ecosystems (forests, agricultural surfaces, urban areas). So will tree species be able to cope with the current global change? Will they be able to migrate to find more favourable conditions or to survive to drier environmental conditions? Firstly, the analysis of historical data (French National Forest Office and Spanish National Forest Inventories) allowed determining colonization and extirpation events, and quantifying migration rates of tree species populations situated at the edges or the core of their distribution range. We evidenced that Q. ilex has substantially colonized new areas at its northern margin during the last 130 years, confirming the model trends. However, the colonization rates of Q. ilex are much lower than the shift of its bioclimate predicted by bioclimatic models. Species located at their rear edge showed higher upward shifts than other species located at the core of their range. To conclude, our results showed that global change have already impacted tree distribution although a time-lag between forest species migration responses and their bioclimate shift. Water stress is the main factor explaining tree dieback when water is limited and so particularly at the warm limit of tree species distribution range. Therefore, we studied drought resistance and its mechanisms in angiosperm tree species. Our results showed that embolism threshold of 90% leads to irreversible damages and tree death by dehydration. This threshold is considerably higher than the observed in Conifers. The study of hydraulic functioning of co-occurring oaks showed that the survival of Q. robur could be threatened in the context of increasing drought in the Atlantic forests because of its functioning at high levels of embolism. On the contrary, Q. ilex presented negligible levels of embolism in the same study area. The migration rates form primordial empirical data that give us information about tree effective migration abilities. They could be integrated within vegetation distribution models as well as embolism thresholds leading to tree mortality.

Tesi realitzada al Instituto Pirenaico de Ecología (CSIC) / Widespread species have traditionally received much less attention than rare and endemic ones. However, they are crucial in macroecological patterns and in ecosystem structure and functioning. Thus, understanding the characteristics that allow widespread organisms to extend over large areas has a high interest from both theoretical and applied perspectives. One of the most frequent hypotheses to explain the success of widespread plants is that they show much wider ecological niches, and thus a high life-history and demographic variability. However, studies are often very specific and carried out over small spatio-temporal scales, which hinders a general understanding of intraspecific variation in widespread taxa. In this thesis, we span a large spatio-temporal scale and a large environmental gradient to analyze the magnitude and the possible causes of natural variation in the in the range centre and the northern periphery of the widespread herb Plantago coronopus. More precisely, we analyze variability in population dynamics, life-history traits, and genetic diversity in up to 22 populations in Europe and North Africa. We aim to explore the relation of such variability with the position of populations within the species’ range, since peripheral populations are traditionally expected to show a lower and more variable performance with respect to central populations. Additionally, we aim to analyze the effects of the most relevant environmental factors in population and individual performance at different spatial scales. In the first chapter, we found higher values in central populations in some vital rates, such as fecundity and growth, but recruitment and density were higher in northern peripheral populations, and there were no clear differences between regions in temporal variability of vital rates. Differences in population performance across the species’ range seemed to be correlated with local precipitation and intraspecific competition. In the second chapter, differences in mean values and variability of vital rates between central and peripheral areas led to no differences in stochastic population growth rates. In addition, recruitment was the most influential vital rate for population growth rates at different spatial scales, and we found the same pattern of differentiation in population dynamics in response to environmental conditions within central and peripheral regions. In the third chapter, we reported high variation among populations in seed traits along a steep environmental stress gradient. Moreover, patterns in seed production were opposite at the fruit and the individual scale, as a strategy of populations to maximize fitness in each set of local conditions. Finally, in the fourth chapter, we found no relationship within populations between phenotypic variability and genetic diversity. Phenotypic variation was mainly shaped by precipitation variability, suggesting adaptive variation, whereas genetic diversity was correlated with the central vs. peripheral position, probably in close relation with some random demographic processes experienced by populations in the past. Despite genetic diversity was higher in central populations, our results contradicted classical hypotheses predicting a lower demographic performance towards species’ range edges. In fact, environmental conditions seemed to have a higher influence on plant performance than the position of populations within the species’ range, which calls for the necessity of distinguishing between geographical periphery and ecological marginality in demographic studies. Overall, our study highlights the versatility of P. coronopus at different spatial scales in response to varying environmental conditions, complementing similar findings of previous research on the same taxon at smaller spatial scales. Such life-history variability seems to be a key factor for widespread plants to extend over large and heterogeneous ranges. / Las especies de amplia distribución han recibido tradicionalmente poca atención, a pesar de su importancia para la estructura y el funcionamiento de los ecosistemas. En esta tesis, se analiza la variabilidad demográfica, de historia vital y genética en una planta de amplia distribución en Europa y el norte de África (Plantago coronopus), en un total de 22 poblaciones a lo largo de gran parte del rango latitudinal de la especie (centro y periferia norte). Se pretende analizar la magnitud y las causas de esta variabilidad intraespecífica en relación con la posición de las poblaciones dentro del rango y con los principales factores medioambientales. Las poblaciones periféricas mostraron una menor diversidad genética, pero no mostraron en general un peor o más variable comportamiento demográfico en cuanto a densidad o tasa de crecimiento poblacional, contradiciendo así las hipótesis clásicas centro-periferia. Se encontró un mismo patrón de diferenciación demográfica dentro de las regiones tanto central como periférica, en relación con la variación en el régimen de precipitaciones. La tasa de reclutamiento de nuevos individuos fue el proceso del ciclo vital con mayor importancia para el funcionamiento de las poblaciones. Se encontró también una gran variación entre poblaciones en las características de las semillas (número, tamaño, mucílago y proporción de dos tipos de semilla dimórficos) en relación con el gradiente de estrés ambiental. Finalmente, la variación fenotípica dentro de las poblaciones se relacionó con la variabilidad ambiental, mientras que la diversidad genética se correlacionó con la posición central vs. periférica de las poblaciones y posiblemente con la historia demográfica de la especie. Globalmente, este estudio muestra la importancia de distinguir entre periferia geográfica y marginalidad ecológica, y sugiere que el éxito de las plantas de amplia distribución reside en una gran variabilidad demográfica y de historia vital a diferentes escalas espaciales.

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