Entender os processos responsáveis pela origem e manutenção da diversidade de espécies nas comunidades representa uma questão central em ecologia. Dos inúmeros processos aventados para explicar a diversidade de organismos, podemos destacar o filtro ambiental e a limitação de similaridade. O filtro ambiental atua restringindo a variação e a distribuição dos organismos em determinado ambiente, enquanto que a limitação de similaridade atua pressionando a diferenciação das características dos organismos, uma vez que a coexistência entre os indivíduos depende da divergência na utilização dos recursos. A abordagem funcional tem sido utilizada para testar os processos responsáveis pela coexistência de espécies e consiste na comparação da similaridade funcional entre as espécies de uma comunidade através da quantificação dos seus atributos. A combinação de diferentes atributos em um organismo define a sua estratégia ecológica e, consequentemente, a sua distribuição nos habitats. As florestas de restingas são ambientes propícios para testar as hipóteses de coexistência das espécies nas comunidades, por apresentarem gradientes ambientes bem marcados e que definem a disponibilidade de recursos. Nesse sentido, este trabalho teve como objetivo avaliar: i) o efeito da condição edáfica (seco e alagado) sobre os atributos funcionais e as estratégias ecológicas de espécies arbóreas de restinga alta e; ii) o efeito que os atributos funcionais e as estratégias ecológicas têm sobre a preferência de habitat pelas plantas. Realizamos este trabalho em uma área de restinga alta na Ilha do Cardoso (SP) que compreende dois tipos de solo: seco e alagado. Coletamos cinco atributos funcionais (área foliar, área foliar específica, espessura foliar, conteúdo de matéria seca foliar e densidade da madeira) de 44 espécies arbóreas. Selecionamos 30 indivíduos de cada espécie sendo 15 em cada tipo de solo. Utilizamos seleção de modelos para as análises estatísticas, sendo usados modelos lineares mistos e modelos lineares simples para avaliar o efeito do solo nos valores médios e na variação dos atributos e das estratégias ecológicas, respectivamente. Encontramos efeito do solo sobre os coeficientes de variação (CV) do conteúdo de matéria seca foliar (CMSF) e da área foliar específica (AFE), sendo maiores no solo alagado. No caso do CV da AFE, o efeito só foi significativo quando excluímos as palmeiras das análises. Não encontramos efeito do solo sobre a variação dos demais atributos funcionais, das estratégias ecológicas e tampouco do tipo de estratégia ecológica. Os resultados encontrados apontam que no ambiente alagado, a limitação de similaridade seja o processo preponderante na estruturação dessa comunidade. Tal resultado difere dos reportados por outros estudos em florestas tropicais. Não encontramos efeito dos atributos e das estratégias ecológicas sobre a preferência de habitat das espécies, com exceção do CV de CMSF e de AFE. Novamente, no caso do CV de AFE, o efeito só foi significativo quando excluímos Euterpe edulis (palmito-juçara) das análises. Este resultado reforça a importância da plasticidade fenotípica para definir a ocorrência das espécies em diferentes habitats / Understanding the processes underlying the origin and maintenance of species diversity in communities is a central goal in ecology. Among the numerous processes proposed to explain the organisms\' diversity, we can highlight environmental filter and limiting similarity. Environmental filter operates by restricting the variation and distribution of organisms in a given environment, while the process of limiting similarity acts by pressing differentiation in the organisms\' characteristics, because the coexistence of individuals depends on difference in resource utilization. The functional approach has been used to test the processes responsible for species coexistence and consists in the comparison of species functional similarities in a community through their traits. The combination of different traits in an organism defines its ecological strategy and, therefore, their distribution on habitats. Restinga forests are suitable to test species coexistence hypotheses in communities, because it presents a well marked environmental gradient, which is defined by resource availability. Thus, this study aimed to evaluate: i) the effect of soil condition (drained and flooded) on functional traits and on ecological strategies of restinga trees species and, ii) the effect of functional traits on plant´s habitat preference. We conducted this study in an area of high restinga at Cardoso Island (SP), which comprises two soil types: drained and flooded. We collected five functional traits (leaf area, specific leaf area, leaf thickness, leaf dry matter content and wood density) of 44 tree species. We selected 30 individuals of each species, 15 in each soil type. We used model selection for statistical analyses, being linear models to assess soil type effect on trait and ecological strategies variances and linear mixed models to assess ecological strategies mean values. We found soil effect on the coefficients of variation of leaf dry matter content (LDMC) and of specific leaf area (SLA), which was higher in the flooded soil. In the case of SLA coefficient of variance, the effect was only significant when we excluded the palms from analyses. We found no soil effect on the other functional traits and on ecological strategies variation, neither on ecological strategy type. As for the results, it was found that in the flooded soil, limiting similarity is the dominant process structuring this community. This result differs from those reported by other tropical forests researches. We found no effect of traits and ecological strategies on habitat species preference, with the exception of LDMC and SLA coefficients of variations. Again, for SLA coefficient of variation, the effect was only significant when we exclude Euterpe edulis (juçara palm) from analyses. This result reinforces the importance of phenotypic plasticity to define species occurrence in different habitats

Entender os processos responsáveis pela origem e manutenção da diversidade de espécies nas comunidades representa uma questão central em ecologia. Dos inúmeros processos aventados para explicar a diversidade de organismos, podemos destacar o filtro ambiental e a limitação de similaridade. O filtro ambiental atua restringindo a variação e a distribuição dos organismos em determinado ambiente, enquanto que a limitação de similaridade atua pressionando a diferenciação das características dos organismos, uma vez que a coexistência entre os indivíduos depende da divergência na utilização dos recursos. A abordagem funcional tem sido utilizada para testar os processos responsáveis pela coexistência de espécies e consiste na comparação da similaridade funcional entre as espécies de uma comunidade através da quantificação dos seus atributos. A combinação de diferentes atributos em um organismo define a sua estratégia ecológica e, consequentemente, a sua distribuição nos habitats. As florestas de restingas são ambientes propícios para testar as hipóteses de coexistência das espécies nas comunidades, por apresentarem gradientes ambientes bem marcados e que definem a disponibilidade de recursos. Nesse sentido, este trabalho teve como objetivo avaliar: i) o efeito da condição edáfica (seco e alagado) sobre os atributos funcionais e as estratégias ecológicas de espécies arbóreas de restinga alta e; ii) o efeito que os atributos funcionais e as estratégias ecológicas têm sobre a preferência de habitat pelas plantas. Realizamos este trabalho em uma área de restinga alta na Ilha do Cardoso (SP) que compreende dois tipos de solo: seco e alagado. Coletamos cinco atributos funcionais (área foliar, área foliar específica, espessura foliar, conteúdo de matéria seca foliar e densidade da madeira) de 44 espécies arbóreas. Selecionamos 30 indivíduos de cada espécie sendo 15 em cada tipo de solo. Utilizamos seleção de modelos para as análises estatísticas, sendo usados modelos lineares mistos e modelos lineares simples para avaliar o efeito do solo nos valores médios e na variação dos atributos e das estratégias ecológicas, respectivamente. Encontramos efeito do solo sobre os coeficientes de variação (CV) do conteúdo de matéria seca foliar (CMSF) e da área foliar específica (AFE), sendo maiores no solo alagado. No caso do CV da AFE, o efeito só foi significativo quando excluímos as palmeiras das análises. Não encontramos efeito do solo sobre a variação dos demais atributos funcionais, das estratégias ecológicas e tampouco do tipo de estratégia ecológica. Os resultados encontrados apontam que no ambiente alagado, a limitação de similaridade seja o processo preponderante na estruturação dessa comunidade. Tal resultado difere dos reportados por outros estudos em florestas tropicais. Não encontramos efeito dos atributos e das estratégias ecológicas sobre a preferência de habitat das espécies, com exceção do CV de CMSF e de AFE. Novamente, no caso do CV de AFE, o efeito só foi significativo quando excluímos Euterpe edulis (palmito-juçara) das análises. Este resultado reforça a importância da plasticidade fenotípica para definir a ocorrência das espécies em diferentes habitats / Understanding the processes underlying the origin and maintenance of species diversity in communities is a central goal in ecology. Among the numerous processes proposed to explain the organisms\' diversity, we can highlight environmental filter and limiting similarity. Environmental filter operates by restricting the variation and distribution of organisms in a given environment, while the process of limiting similarity acts by pressing differentiation in the organisms\' characteristics, because the coexistence of individuals depends on difference in resource utilization. The functional approach has been used to test the processes responsible for species coexistence and consists in the comparison of species functional similarities in a community through their traits. The combination of different traits in an organism defines its ecological strategy and, therefore, their distribution on habitats. Restinga forests are suitable to test species coexistence hypotheses in communities, because it presents a well marked environmental gradient, which is defined by resource availability. Thus, this study aimed to evaluate: i) the effect of soil condition (drained and flooded) on functional traits and on ecological strategies of restinga trees species and, ii) the effect of functional traits on plant´s habitat preference. We conducted this study in an area of high restinga at Cardoso Island (SP), which comprises two soil types: drained and flooded. We collected five functional traits (leaf area, specific leaf area, leaf thickness, leaf dry matter content and wood density) of 44 tree species. We selected 30 individuals of each species, 15 in each soil type. We used model selection for statistical analyses, being linear models to assess soil type effect on trait and ecological strategies variances and linear mixed models to assess ecological strategies mean values. We found soil effect on the coefficients of variation of leaf dry matter content (LDMC) and of specific leaf area (SLA), which was higher in the flooded soil. In the case of SLA coefficient of variance, the effect was only significant when we excluded the palms from analyses. We found no soil effect on the other functional traits and on ecological strategies variation, neither on ecological strategy type. As for the results, it was found that in the flooded soil, limiting similarity is the dominant process structuring this community. This result differs from those reported by other tropical forests researches. We found no effect of traits and ecological strategies on habitat species preference, with the exception of LDMC and SLA coefficients of variations. Again, for SLA coefficient of variation, the effect was only significant when we exclude Euterpe edulis (juçara palm) from analyses. This result reinforces the importance of phenotypic plasticity to define species occurrence in different habitats

La problématique de ce travail concerne des cas concrets d'application de l'approche paléobiologique chez les ammonites. Une attention spéciale a été donnée à la variabilité intraspécifique et ses conséquences taxinomiques, ainsi qu'à l'étude des patterns et processus évolutifs des groupes étudiés, afin d'en tirer des généralités. Les études paléobiologiques sur des exemples très variés montrent que la variabilité et le degré de sa prise en compte par les auteurs a une influence particulière sur les conceptions taxinomiques, et par conséquent sur la biostratigraphie et sur la compréhension des mécanismes évolutifs. Les lois de Westermann semblent être prépondérantes pour expliquer la variabilité intraspécifique d'un grand nombre de groupes d'ammonites, mais elles ne sont pas la seule source de covariation et leur influence doit être relativisée face à d'autres facteurs habituellement peu pris en compte. Les facteurs de la variabilité intraspécifique reconnus concernent : (1) le dimorphisme, (2) une variabilité dipolaire dans l'application stricte de la première loi de Westermann, (3) des variation par rapport à l'énoncé général de cette loi, (4) une variabilité tripolaire, (5) des relations hétérochroniques morphologiques dépendantes ou indépendantes, (6) un facteur d'atténuation de l'ornementation, et (7) différents facteurs d'enroulement liés ou non à d'autres caractères morphologiques et ornementaux chez les ammonites hétéromorphes. / The issue of this work involves concrete case of application of the palaeobiological approach in ammonites. Special attention was given to intraspecific variability and its taxonomic consequences and the study of evolutionary processes and patterns of the groups studied, in order to draw generalizations. Paleobiological studies on a variety of examples show that the degree of variability and its consideration by the authors has a particular influence on taxonomic concepts, and consequently on the biostratigraphy and the understanding of evolutionary mechanisms. Westermann laws seem to be dominant to explain intraspecific variability of a large number of ammonites groups, but they are not the only source of covariation and their influence must be relativized against other factors usually not taken into account. Factors of intraspecific variability recognized are: (1) dimorphism, (2) a dipolar variability in the strict application of the first Westermann’s law, (3) changes compared to the general statement of the law, (4) tripolar variability, (5) heterochronic relationships morphological dependent or independent, (6) an attenuation factor of ornamentation, and (7) various coiling factors related or not to other morphological and ornamental characters in heteromorphic ammonites.

5 Abstract Morphological traits give information about the adaptations of the studied species, the resources, which it uses, and they can generally tell us about the use of ecological space. Intraspecific morphological variability reflects various adaptations of local populations thus variability reflect different way of life. The subject of this thesis is an ecologically interesting group of specialized tropical songbirds - Sunbirds (Nectarinidae). The taxon exhibits number of adaptations to specific food collecting a combination of nectarivory and insect hunting. I focused here on the intraspecific variability of three species (Cyanomitra oritis, Cinnyris reichenowi and C. bouwieri) living in different habitats in Cameroon. The aim of this work was to find out in what morphological characters are this species sexually dimorphic. Furthermore, if their populations living in remote locations differ? Finally, if all studied species show similar trend of intraspecific variability of the traits, which could have common ecological causes. The following traits were measured: wing and tail feather length, beak dimensions, total body weight and other characters. The analysis is based on field data collected between 2003 and 2015 and museum collections. Overall, we collect information about ca. 1200 individuals for...

Chez les diatomées du genre Pseudo-nitzschia, certaines espèces produisent une neurotoxine, l’acide domoïque responsable chez l’homme d’intoxications amnésiantes suite à la consommation de mollusques contaminés. En Baie de Seine, la variabilité interannuelle de ces efflorescences toxiques, qui provoquent certaines années des fermetures de zones de pêche à la coquille Saint-Jacques, est liée à des changements de diversité spécifique au sein des communautés de Pseudo-nitzschia. Cette thèse avait pour objectif de caractériser la diversité écophysiologique au sein du genre Pseudo-nitzschia afin de mieux comprendre les facteurs qui influencent les différences de toxicité et de phénologies des efflorescences des principales espèces de Pseudo-nitzschia de Baie de Seine. Différents paramètres physiologiques, tels que la croissance, la production d’acide domoïque, les quotas élémentaires, les paramètres photosynthétiques, ainsi que les paramètres de cinétiques d’absorption du nitrate, du silicate et du phosphate, ont été étudiés chez quatre espèces : P. australis, P. pungens, P. fraudulenta et P. delicatissima. De plus, la variabilité intraspécifique a été évalué en étudiant de nombreuses souches par espèce et en estimant l’influence des variations de la taille cellulaire liées au cycle de vie de Pseudo-nitzschia sur les paramètres physiologiques. Les résultats montrent une importante diversité intraspécifique de la physiologie des quatre espèces, en partie liée à la taille cellulaire et parfois au cycle de vie. La connaissance de cette diversité intraspécifique a permis de caractériser différents traits physiologiques pour chaque espèce. Les résultats apportent des éléments de compréhension sur les conditions physiologiques favorables à la production d’acide domoïque et le rôle des éléments nutritifs dans le déterminisme des efflorescences des espèces de Pseudo-nitzschia. / In the diatom Pseudo-nitzschia, some species produce a neurotoxin called domoic acid responsible for amnesic shellfish poisoning in humans following the consumption of contaminated molluscs. In the Bay of Seine (English Channel), the variability of bloom toxicity is linked to differences in the Pseudo-nitzschia species diversity. The aim of this thesis was to characterize the ecophysiological diversity within the genus Pseudo-nitzschia in order to better understand the physiological parameters influencing differences in toxicity and bloom phenology among the main Pseudo-nitzschia species of the Bay of Seine. Growth, domoic acid production, elemental intracellular quotas, photosynthetic parameters and kinetic parameters for nitrate, phosphate, and silicic acid uptake were studied in four Pseudo-nitzschia species: P. australis, P. pungens, P. fraudulenta et P. delicatissima. The intraspecific variability was characterized with a multi-strain approach and also considering the effect of cell size on the studied physiological parameters. The results highlight the importance of the intraspecific variability in the physiology of the four species, in part due to cell size reduction linked to Pseudo-nitzschia life cycle. Delineate the intraspecific diversity allowed to characterize different physiological traits for each species. This work brings new information on the physiological conditions favorable to domoic acid production and on the role of nutrients in controlling Pseudo-nitzschia species diversity during blooms.

Les risques de sécheresse sévère augmentent sous l’effet du changement climatique. Mieux comprendre les stratégies adaptatives des plantes au stress hydrique est ainsi l’un des défis majeurs de la recherche écologique et agronomique. Cette thèse explore la survie à la sécheresse d’une graminée herbacée pérenne (Dactylis glomerata L.) en étudiant la variabilité intraspécifique des traits aériens et souterrains d’une quinzaine de populations natives et cultivées issues d’un gradient latitudinal allant de la Scandinavie au Maroc. Une caractérisation des populations en conditions optimales sur une année a montré une coordination phénologique des traits aériens en relation avec les limitations saisonnières de croissances liées à l’origine des populations. Le rythme de croissance au printemps et à l’automne ne discrimine pas les origines, alors que la dormance estivale des populations méditerranéennes s’oppose à la dormance hivernale des populations scandinaves. Ces résultats suggéraient l’existence d’un compromis entre survie à une déshydratation sévère (sécheresse, gel) et potentiel de croissance. Alors que ce compromis a été vérifié en été (sècheresse sévère à Montpellier) et en hiver (gel en Norvège), la survie à une déshydratation de contre-saison au printemps n’est pas corrélée au potentiel de croissance des populations. Les résultats invalident donc l’existence d’un compromis constant entre survie au stress et potentiel de croissance aérienne. Ce découplage chez le dactyle permet d’envisager la sélection artificielle, à partir de la variabilité intraspécifique existante, de variétés à la fois productives et tolérantes au stress hydrique. L’imposition d’une déshydratation édaphique sévère en pots limitant l’expansion du système racinaire a montré que les populations méditerranéennes survivent mieux que les populations tempérées ou nordiques. L’association de ces résultats avec ceux issus d’une expérimentation en longs tubes favorisant le développement potentiel des racines révèle un compromis entre les stratégies d’évitement de la déshydratation (acquisition de l’eau et maintien de la croissance) et de tolérance à la déshydratation (faible croissance et forte survie à la sécheresse) qui pourrait limiter la combinaison de stratégies adaptatives au sein d’un même phénotype. Cette thèse contribue à améliorer notre compréhension des compromis fonctionnels, peu étudiés à l’échelle intraspécifique, mais qui sous-tendent la réponse des plantes à la sécheresse. / Drought risk increases with climate change. Improving our understanding of the adaptive mechanisms of plants response to drought has thus become one of the major challenges of ecological and agronomical research. This work investigates the drought survival of a perennial herbaceous species (Dactylis glomerata L.) through the intraspecific variability of above and below ground traits expressed by fifteen native and cultivated populations originating from a large latitudinal gradient, from Scandinavia to Morocco. Population traits characterization across one year under optimal growth conditions showed phenological coordination of above ground traits associated with seasonal growth limitations according to the origins of the populations. The spring growth rhythm does not discriminate origins while the summer dormancy of Mediterranean population contrasts with the winter dormancy of Scandinavian populations. These results suggested a growth-dehydration stress survival trade-off. Although this trade-off was confirmed in summer (severe drought in Montpellier) and winter (severe frost in Norway), no correlation was found between an off-season (spring) drought stress survival and populations’ growth potential. The result invalidates the existence of a constant trade-off between stress survival and aerial growth potential. This apparent decoupling in cocksfoot could be considered to produce new cultivars with both high productivity and high drought tolerance, from existent intraspecific variability. A severe dehydration stress imposed on plants grown in short pots, limiting roots expansion, showed that Mediterranean populations survived better than temperate or Nordic populations. In association with a long tube experiment allowing full expression of roots development, this result revealed a functional trade-off between dehydration avoidance (water acquisition and growth maintenance) and dehydration tolerance (low growth and high drought survival) which could limit the combination of adaptive strategies in a single phenotype. This work contribute to improve our knowledge about functional trade-offs, few studied within species, that underpin plant response to drought stress.

Plusieurs études ont montré que la productivité des forêts et des cultures décroît sur l’ensemble de la planète en réponse au changement climatique, et que les risques de mortalité liée à la sécheresse s’accroissent. Ces mortalités massives ont été observées dans tous les écosystèmes forestiers et seraient dues à un dysfonctionnement hydraulique des plantes, causé par de l’embolie xylémiène. Le spectre interspécifique de résistance à l'embolie a été largement étudiée, mais peu d'attention a été accordée à la variabilité intra-spécifique de ce trait. C’est pourquoi, l’objectif de ce travail de thèse était d’améliorer notre compréhension de la variabilité intra-spécifique de la résistance à l’embolie chez une espèce cultivée(Helianthus annuus L.) et chez un conifère (Pinus pinaster). Nous avons déterminé la vulnérabilité à l’embolie de quatre variétés de tournesol, présentant des différences significatives de P50 (pression induisant 50% de perte de conductivité hydraulique), allant de -2.67 à -3.22 MPa. Un compromis entre sécurité hydraulique et croissance a été observé mais pas entre la sécurité hydraulique et la capacité de transport de l'eau du xylème. Seuls quelques caractères anatomiques, tels que la densité des vaisseaux et la surface du lumen, présentent une corrélation avec la résistance à l’embolie. Dans un second temps, nous avons phénotypé pour la résistance à l’embolie et la densité du bois 477 génotypes de P. pinaster, issus d’une F2 de pleins-frères correspondant à la 3ème génération consanguine obtenue par auto-fécondation d’un hybride inter-provenance “Corse × Landes. La variabilité de la P50 au sein de l’espèce était extrêmement faible (CVP=5.6%). D’autre part, nous avons mis en évidence l’absence de compromis entre sécurité hydraulique et densité du bois. La part de variance du caractère P50 expliquée par QTLs (PEV)correspondait à 23.6% de la variance phénotypique totale mais aucun QTL commun n’a pu être détecté entre P50 et densité du bois, suggérant qu’au sein de cette famille, la plus forte résistance à l’embolie de certains génotypes n’est pas liée à un bois plus dense. Une analyse multi-caractère du fonctionnement de la feuille et du xylème a été réalisée via l’étude de la dynamique saisonnière de la fluorescence du photosystème II et des traits hydrauliques de la tige, sur une famille de pleins-frères d’un hybride interprovenance “Maroc × Landes” de P. pinaster ; en réponse à une diminution du potentiel hydrique,l’efficience du photosystème II et la conductance stomatique ont tous deux diminué, induisant une décroissance rapide du taux d’assimilation. La résistance à l’embolie du xylème n’a pas montré de relation significative avec les traits foliaires. L’absence de compromis entre ces caractères permet donc d’envisager la sélection génétique de génotypes à la fois efficients et résistants. / As a consequence of current global climate change, forest and crop ecosystems are decreasing inproductivity worldwide and are under increased threat of widespread drought-induced mortality due tohydraulic failure caused by xylem embolism. The range of embolism resistance across species has been intensively studied but little attention has been paid to intraspecific variability. This thesis aimed thereforeat improving our understanding of the intraspecific variation in embolism resistance in one crop species(Helianthus annuus L.) and one conifer species (Pinus pinaster). In the first place, vulnerability to embolism was determined across four sunflower accessions with significant variations in P50 (pressure inducing 50% loss of hydraulic conductivity) ranging between -2.67 and -3.22 MPa. A trade-off between hydraulic safety and growth was observed but not between hydraulic safety and efficiency. Only few anatomical traits, such as vessel density and vessel lumen area, were found related to embolism resistance.Secondly, we phenotyped 477 P. pinaster full-sib F2 genotypes corresponding to a three-generation inbred pedigree obtained by the self-pollination of an inter “Corsica × Landes” provenance hybrid, for embolismresistance and wood density. The variability for P50 within species was remarkably low (CVP=5.6%). Wealso found a lack of trade-off between hydraulic safety and wood density. The phenotypic variance explained by QTLs (PEV) detected for P50 accounted for 23.6% of the phenotypic variation but no QTL collocated between P50 and wood density, suggesting that embolism resistant genotypes in this family are not dependent on denser wood. A multi-trait analysis of leaf and xylem functioning was performed through seasonal measurements of photosystem II fluorescence and stem hydraulic traits on a full-sib family of aninter “Morocco × Landes” provenance hybrid of P. pinaster; it revealed that with decreasing water potential, the efficiency of both photosystem II and stomatal conductance decreased which resulted in rapid decrease in assimilation rate. Xylem resistance to embolism was found having no relationship with leaf functioning traits. The absence of trade-off between these traits makes it possible to consider selection for both efficient and resistant genotypes.

Sept accessions représentant la diversité génétique du Sorgho (Sorghum bicolor) ont été cultivées dans une condition de carence (N⁻) et une condition non-limitante (N⁺) en nitrate. Les paramètres de croissance (taille de la plante et le nombre de feuilles), les paramètres physiologiques (teneur en nitrate, teneur en protéines, concentrations totales en carbone et azote) et l'activité de la glutamine synthétase (GS) ont été mesurés dans les feuilles et les racines des plantes de sorgho à trois stades précoces de développement végétatif (2, 4 et 6 semaines après germination). Les résultats montrent que : i) les valeurs obtenues pour l’ensemble des paramètres sont généralement plus faibles en situation de carence en nitrate ; ii) la taille des plantes et le nombre de feuilles sont plus grands sous un régime non-limitant ; iii) tous les paramètres étudiés sauf la teneur en Carbone, étaient sensibles à la disponibilité en azote. Cependant, les différents génotypes étudiés affichent de grandes variations dans leurs réponses aux deux conditions de cultures. On observe une variation de la taille des plantes entre les génotypes au cours du développement végétatif précoce, mais pas pour le nombre de feuilles. De même, on observe une grande variation dans les réponses physiologiques entre les différents génotypes. Des corrélations fortes et significatives ont été détectées entre la taille des plantes et la teneur en nitrate. Cependant ces corrélations varient selon les conditions de cultures et les génotypes étudiés. En outre, la teneur en nitrate et l'activité GS mesurés aux stades précoces de croissance, semblent être de bons marqueurs pour discriminer entre les différents génotypes pour leur aptitude à absorber ou assimiler les nitrates dans les deux conditions de cultures. L’expression dans les feuilles et racines de deux génotypes de sorgho, de deux copies d’un gène candidat pour l’efficacité d’utilisation d’azote, SbNRT1.1 codant pour un transporteur de nitrate, varie en fonction de la disponibilité en nitrate, de l’organe et de l’âge de la plante. Notre étude constitue une première contribution à l’analyse de l’efficacité d’utilisation d’azote chez le sorgho par une approche physiologique et une approche génétique. Les résultats obtenus ouvrent des perspectives pour de futures études fondamentales mais aussi des recherches finalisées qui conduiront à l’identification de génotypes valorisant mieux l’azote. / Seven accessions of Sorghum bicolor were grown with low (N⁻) and optimal (N⁺) nitrate supply. Growth parameters (plant height and leaf numbers), physiological parameters (nitrate, protein, total N and total C contents) and the activity of glutamine synthetase (GS) were studied in leaves and roots of sorghum plants at three time points of early vegetative growth (2, 4 and, 6 weeks post emergence). Plant height and leaf number were higher with nitrate supply. Except for carbon, all studied parameters were sensitive to N availability and values were typically lower when nitrate supply was low. However, different genotypes displayed considerable variation in their response to N regimes. Variation among genotypes during early vegetative development was observed for plant height, but not for leaf number. Likewise, physiological parameters varied among accessions. A significant and strong correlation, N- and accession-dependent, was detected between plant height and nitrate content. Moreover, nitrate content and GS activity at early growth stages appeared to be good markers to discriminate between nitrate uptake and assimilation capacities of different accessions under both N conditions. In some sorghum accessions, protein and total N content were indicative of high nitrate reduction and assimilation even under N limitation. Chlorophyll content was also sensitive to N availability. Furthermore, expression studies of SbNRT1.1gene copies in leaves and roots of two accessions reflected variability in expression dependent on nitrogen condition, plant organ, plant age, and gene of interest. This study is helpful to characterize different aspects of the N metabolism in sorghum and may aid in the identification of sorghum genotypes with enhanced nitrogen use efficiency, a trait that is of key interest in one of the most important crop plants in arid and semi-arid regions.

Interspecific and intraspecific size variability of the skull, mandibles and teeth of the lesser white- toothed shrew Crocidura suaveolens and the bicolored white-toothed shrew C. leucodon was studied on material of 350 skulls and 465 mandibles of white-toothed shrews obtained by analysis of the barn owl pellets originating from four regions in the Czech Republic and one region in the southern Slovakia. C. suaveolens was present in all regions under study, while sympatric C. leucodon occurred in three regions only. In total, 21cranial and dental measurements and 4 mandibular measurements were investigated. It was found that the most reliable measurement enabling discrimination between skulls of both species in the whole studied material is the lenght of the lower dental row. If skulls of both species were evaluated separately for each area of their sympatry it was possible to use also the distance between second molars M2 and the width of premolar P4 . Skulls of these two species can also be distinguished by bivariate graphs using the length and width of premolar P4 and the palatal length. We studied relationships between cranial measurements of both species and geoclimatic factors such as longitude, latitude, mean annual temperature and mean annual percipitation. It was found that variability of...

Neophobia and exploratory behaviour are two processes applied in great measure in birds' reactions towards novel stimuli. The specific demonstration of these two processes may differ between different species of birds as well as within them. We compared neophobia and exploratory behaviour in two species of tits (Paridae). Adult Great tits (Parus major) and Blue tits (Cyanistes caeruleus) did not differ neither in exploring novel environment and novel object nor in neophobia towards novel object near food. We have found great differences between juveniles of these two species. Juvenile Blue tits were more neophobic towards both novel objects. Age, sex and personality affected some differences within tested species. We tested whether there exist any differences in reactions towards novel food between and within species. We used red painted mealworm (larvae of Tenebrio molitor), house cricket (Acheta domestica) and aposematic bug (Pyrrhocoris apterus) as novel food. Adult wild-caught tits with plentiful experience with various feeds did not differ in reaction towards these types of novel food. In contrast hand-reared juvenile tits differed quite a lot. Juvenile Blue tits were more neophobic than juvenile Great tits towards all three types of novel food. We found dieraty conservatism, phenomenon...