Accroître la biodiversité dans les agroécosystèmes est une stratégie écologique qui permettrait de rendre les productions plus durables. Une des pistes prometteuses est la culture en association de deux espèces sur une même parcelle et pendant une durée significative de leur cycle de développement. Ces cultures associées et notamment les mélanges céréalelégumineuse présentent de nombreux avantages, en particulier dans les systèmes à faible disponibilité en azote, en termes de production, de qualité et de bénéfices environnementaux. Ces performances sont étroitement liées à l’expression des complémentarités de niche et la réduction des effets de compétition entre les composantes de l’association. Les interactions interspécifiques dépendent fortement des caractéristiques phénotypiques (physiologie, morphologie, phénologie) des espèces et variétés associées. L’objectif de notre travail était d’étudier l’effet de la variabilité génotypique de espèces sur les performances des cultures associées de blé dur-légumineuse à graine et d’analyser le comportement des cultivars vis-à-vis des interactions inter et intra-spécifiques. Pour cela, nous avons mis en place deux expérimentations de 2011 à 2013 afin de tester plusieurs combinaisons de variétés présentant des traits phénotypiques différents. Chaque variété a été semée en culture pure en densité normale et en demi-densité (afin d’étudier les interactions intra-spécifiques) et en association de type substitutive (les deux espèces sont semées en demi densité et en mélange sur le rang) afin d’étudier les interactions interspécifiques. Nos résultats ont confirmé que le comportement d’un génotype est variable entre culture pure et association et que la performance d’une espèce en association dépendrait de sa performance en culture pure mais aussi de sa compétitivité. Ce pouvoir compétitif est sensible aux traits phénotypiques de chaque espèce et à la variation des conditions pédoclimatiques. Une analyse de la dynamique des interactions interspécifiques montre qu’à partir de la période de floraison des légumineuses, les compétitions deviendraient plus intenses et pourraient influencer les rendements en grains. In fine, ce travail nous a permis d’identifier des traits marqueurs de la performance des légumineuses en association qui serviront à concevoir des idéotypes adaptés aux couverts plurispécifiques afin d’optimiser les services rendus par ces systèmes cultivés. / Increasing biodiversity in agroecosystems may contribute to a sustainable productions. Intercropping, the growth of two or more species in the same space at the same time, is considered as a practical application of ecological principles based on biodiversity. Grain legume-cereal intercropping reveals many potential advantages in productivity, stability of outputs and ecological sustainability particularly in low N-input systems. These advantages occur when intercrop components have a complementary ecological niches and competitive interaction are reduced. Interspecific interactions are greatly influenced by phenotypic traits (physiological, morphological and phenological) among cultivars and species. The aim of our study is to study the effect of genotypic variability of species on the performance of durum wheat-grain legume intercrops and to analyze the response of cultivars toward inter and intraspecific interactions. An experimental trial was carried out during two years (2011 to 2013) to test different cultivar combinations. Each cultivar and specie was cultivated as sole crop, half density sole crop and intercrop in a replacement design to evaluate inter- and intra-specific interactions. Our results confirmed that genotype behavior is different between sole crop and intercropping. The intercrop performance is dependent on its performance on sole crop and on its competitiveness. Phenotypic traits and pedoclimatic conditions influence the competitive ability of intercrops. Besides, a dynamic analysis of interspecific interactions shows that from the legumes flowering period, competitions would be the most intense and would impact the grain yield. Finally, this study has allowed to identify some indicators of the performance of grain legumes on intercropping that would help to concept ideotypes adapted to multispecies systems in order to optimize their advantages.

La polyploïdie est un processus important et un moteur de la diversification et de l'évolution des plantes. Peu de polyploïdes naturels ont été décrits chez Juniperus, un genre de conifère représenté par 75 espèces d'arbres ou arbustes à feuilles persistantes, largement réparties dans l'hémisphère nord. Dans ce travail de recherche, l’implication de la polyploïdie dans l'évolution de Juniperus et l’élucidation des mécanismes sous-jacents à ces événements de polyploïdisation sont explorées. La taille du génome (TG) et le niveau de ploïdie ont été évalués chez 111/115 taxons en utilisant la cytométrie en flux et les comptages chromosomiques. Le taux de polyploïdie chez les genévriers s’est avéré être exceptionnellement élevé : 15 taxons sont des tétraploïdes et un seul taxon (J. foetidissima) est hexaploïde. Juniperus foetidissima représente le seul conifère hexaploïde découvert à ce jour à part Sequoia sempervirens. Nous avons également utilisé des approches de modélisation phylogénétique pour déterminer la TG ancestrale dans les trois clades de Juniperus et pour reconstruire le processus évolutif de la polyploïdisation chez ce genre. Au moins 10 événements de polyploïdisation ont eu lieu au cours de l'évolution et de la diversification de Juniperus. Nous avons ensuite exploré l’origine de la polyploïdie chez certaines espèces méditerranéennes. La variation de la TG et le niveau de ploïdie de deux variétés de J. sabina ont été estimés : Les populations échantillonnées de J. sabina var. sabina se sont avérées être diploïdes, tandis que les populations de J. sabina var. balkanensis étaient toutes tétraploïdes. Ces derniers auraient été issus d'une ancienne hybridation entre le tétraploïde J. thurifera et le diploïde J. sabina. Dans les Alpes françaises, où J. sabina var. sabina et J. thurifera sont en sympatrie, des individus présentant des morphologies intermédiaires entre ces deux espèces sont observés. Suite à des estimations des TG, de séquençage des ITS et de régions chloroplastiques, ces individus sont considérés comme des hybrides triploïdes. Enfin, l’utilisation des marqueurs AFLP pour déchiffrer les relations phylogénétiques entre des espèces méditerranéenne a montré que plusieurs pools génétiques contribuent à la diversité de Juniperus. Aussi ces marqueurs ont contribué à la découverte des contributions de ces pools génétiques aux taxons polyploïdes. Alors que les populations libanaises de l'hexaploïde J. foetidissima sont issues d'une lignée ancestrale unique, la population grecque semble résulter d'un mélange inégal de deux lignées anciennes. Ces deux lignées contribuent également au tétraploïde J. thurifera. Cette analyse a également montré que l’espèce méditerranéenne J. excelsa et l’espèce africaine J. procera partagent la même lignée ancestrale. Cependant, des analyses supplémentaires sont nécessaires pour une interprétation plus complète des données. L'importance de l'hybridation interspécifique et de la polyploïdie dans l'évolution des espèces de Juniperus nécessite d’amples recherches visant à comprendre le lien entre ces mécanismes et l'adaptation de ces espèces à un large spectre d'habitats extrêmes. Ces recherches futures devraient aussi contribuer à découvrir comment les espèces de conifères peuvent s’adapter aux changements climatiques. / Polyploidy is considered as an important phenomenon and a key driving force for plant diversification and evolution. Few natural polyploid species have been described in Juniperus, a coniferous genus represented by 75 species of evergreen trees or shrubs widely distributed in the North Hemisphere. The occurrence of polyploidy in the evolution of this genus as well as a more comprehensive view of pathways that were involved in these polyploidization events are explored in this research work. Genome size (GS) and ploidy level assessments were conducted on 111/115 taxa using flow-cytometry and chromosome counts. Juniperus holds an exceptionally high rate of polyploidy, 15 taxa being tetraploids and just one (J. foetidissima) being hexaploid. It represents the only hexaploid conifer discovered to date after Sequoia sempervirens. We also used phylogenetically-informed trait evolution modelling approaches to determine ancestral GS in the three clades of Juniperus and to reconstruct the evolutionary process of polyploidization in Juniperus. At least 10 polyploidization events have occurred during Juniperus evolution and diversification. We then explored the origin of polyploidy in selected Mediterranean species. The GS variation and the ploidy level of two J. sabina varieties were estimated: J. sabina var. sabina sampled populations were shown to be diploid, while J. sabina var. balkanensis populations were all tetraploid. The latter has been postulated to have arisen from an ancient hybridization between the tetraploid J. thurifera and the diploid J. sabina. In the French Alps, where J. sabina var. sabina and J. thurifera occur in sympatry, individuals with intermediate morphologies between these two species are observed. Evidences based on GS assessments, ITS and chloroplastic sequences demonstrated these individuals as triploid hybrids. Finally, the use of AFLP markers to decipher phylogenetic relationships between Mediterranean and Eastern Mediterranean species showed that multiple lineages contributes to Juniperus diversity and shed light on some polyploid taxa origins. While the Lebanese populations of the hexaploid J. foetidissima are issued from a unique ancestral lineage, the Greek population seems to be the result of an unequal admixture of two ancient lineages. These two lineages contribute also to the tetraploid J. thurifera. This analysis showed also that the Mediteranean J. excelsa and the African taxa J. procera shares the same ancestral lineage. However, further analyses are needed for a more complete interpretation of the data. The importance of interspecific hybridization and of polyploidization in the evolution of Juniperus species argues in favor of the development of researches aiming at understanding the link between these mechanisms and the adaptation of those species to a wide range of extreme habitats. Such future researches should contribute to predict how conifer species may adapt to dramatic changes in the Earth’s climate.

Hybridization is an important phenomenon in plant evolution because it is one of the sources of new genetic variability. Hybridization is the merging of genomes of formerly isolated evolutionary lineages. In many taxonomic groups, the detection of plants of hybrid origin is challenging. A wide spectrum of methods for their detection has been employed since the beginning of botanical research. The introduction of genomic in situ hybridization has had a great impact on the study plants of hybrid origin. This molecular cytogenetic approach allows to reveal the genomic contributions of particular parental species to hybrid taxa. The tribe Triticeae is a prime example of a group whose present-day diversity has been strongly influenced by hybridization (together with polyploidy). The majority of its species are allopolyploids resulting from frequent interspecific and intergeneric hybridization. The structure of relationships within the tribe is therefore highly reticulate. This thesis includes three papers dealing with the hybrid complex of Elytrigia repens - E. ×mucronata - E. intermedia: (1) The representatives of this hybrid complex are morphologically poorly differentiated, and only two morphological characters are used to their distinguishing. Among anatomical characters on the leaf blade, some...

Hybrid sterility is one of the reproductive isolation mechanisms restricting gene flow between the related species and leading to speciation. PR domain containing 9 (Prdm9), the only known vertebrate hybrid sterility gene, determines the sites of programmed DNA double-strand breaks (DSBs) and thus specifies hotspots of meiotic recombination but in hybrids between two mouse subspecies causes failure of meiotic chromosome synapsis and hybrid male sterility. In the present study on sterile hybrids, the five smallest autosomes were more prone to asynapsis. To manipulate with the synapsis rate, random stretches of consubspecific homology were inserted into several autosomal pairs. Twenty seven or more megabases of consubspecific sequence fully restore synapsis in a given autosome. Further, at least two symetric DN double-strand breaks per chromosome were necessary for successful synapsis. Moreover, F1 hybrids had sperm when synapsis was rescued in at least three of four segregating chromosomes. To verify the assumption of a lack of symmetric DSBs in meiotic chromosomes of sterile males the chemotherapeutic drug cisplatin was used to induce exogenous DNA DSBs. Cells treated with 5 mg/kg and 10 mg/kg of cisplatin showed increased number of DSBs monitored by immunostaining of RPA and DMC1 sites and...

Marine turtles exhibit strong fidelity to their nesting beaches, making the conservation of nesting beaches important for ensuring successful sea turtle populations. Conservation of these nesting beaches involves understanding how species interact with the environment and each other, and understanding how environmental change and population growth can affect the suitability of the nesting habitat. The Archie Carr National Wildlife Refuge (ACNWR) is unusual in its high density of sea turtle nesting by two species: green (Chelonia mydas) and loggerhead (Caretta caretta) turtles. The ACNWR in Melbourne Beach, Florida was established in 1991 due to the high density of loggerhead nesting, but in the time since it was established there has been a significant increase in green turtle nesting, from fewer than 50 nests in 1982 to over 15,000 in 2017. With such a high density of these two species in one relatively small area (21 kilometers of beach), the two species may compete for space. This is especially true for green turtles, which disturb large amounts of sand during their nesting process; in 2017, we observed 338 loggerhead clutches disturbed by nesting females during nesting surveys, nearly all of which were disturbed by green turtles. Using observed spatial and temporal nesting patterns for both green turtles and loggerheads on the ACNWR, I examined the effects these species may have on each other's nests now and in the future. Additionally, green turtles and loggerheads nest in different densities along the length of the ACNWR, with green turtles more concentrated in the southern portions of the Refuge. Finally, green turtle nesting begins and peaks approximately one month later on the ACNWR than loggerhead nesting. For each of these metrics, there is both considerable overlap and distinct separation between the two species. By using these metrics in a modeling approach, I estimated the probability of nest disturbance by a subsequently nesting female, ranging from 0 to 0.105, and how these probabilities are predicted to change over time with a growing green turtle population. Evaluating the carrying capacity of this beach is important in the context of habitat disturbance, including climate change and an increase in storm frequency, and informing adaptive management strategies for effective conservation.

No description available.

Social behaviour is shaped by complex relationships between evolutionary and ecological processes interacting at different scales. Benefits gained from social associations can range from predator dilution to collective sensing, but little is known about how these can be influenced by social structure and phenotypic composition. In this thesis, I investigated how individual decision-making affects phenotypic social structure, and how this mediates social behaviour through emergent properties of collective group behaviour. First, using mixed-species flocks as a model system, I showed individual tits (Paridae, chapter 2) and thornbills (Acanthizae, chapter 3) varied significantly in their social positions. Within-species variation in network position was as large as between-species variation, sug- gesting that prescribing functional roles at the species level may not sufficiently account for potential differences in fitness operating at the individual level. Rather, this suggested that structure may be driven by phenotypic traits, underpinning network structure (chapter 4). Next, I used an extensive data set of foraging records to explore factors determining the composition, of flocks of great tits (Parus major, chapter 5). For example, assortment by dispersal phenotype (immigration status) was the result of spatial disaggregation, and I showed that this may facilitate social selection for breeding territories (chapter 6). Finally, I investigated how decision-making shaped mixed-species social structure. I found that tits used a common strategy for managing pressures of predation and starvation by shifting from exploration to exploitation at different times of the day (chapter 7). I then found that a very simple interaction rule successfully replicated mixed-species group structure (chapter 8). Strikingly, the same rule was applied to both conspecifics and het- erospecifics, potentially playing an important role in the maintenance of flock structure. Through experimental manipulation of ecological conditions, I found that heightened per- ceived predation resulted in stronger social attraction overall, whereas increased competition led to a reduction in attraction to conspecifics (chapter 9). Simulations suggested this could be one potential mechanism underpinning fission-fusion dynamics in these species. Together, the results in this thesis form a framework linking social behaviour to individ- ual fitness where natural selection is shaped by the social environment. This approach may prove useful for testing whether following common social rules reduces variance in benefits accrued by individuals, and how within-species variation in social behaviour can impact emergent properties of groups.

Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Shifts in species ranges are an important consequence of climate change, and can affect the composition, structure and functioning of ecosystems. Generally, in response to rising temperatures, species have increased their altitudinal and latitudinal distributions along their cooler boundaries, although there has been large variation between species. However, in addition to climatic factors, species range limits are also sensitive to biotic interactions. Therefore, interspecific interactions may be able to influence the impact of climate change on species distributions. In this thesis climate change, range shifts and spatial variation in plant-plant interactions are documented to examine the potential for biotic interactions to mediate climate-driven altitudinal range shifts on sub-Antarctic Marion Island. The climate on Marion Island changed considerably between 1949 and 2003, with significant trends in biologically-relevant parameters encompassing average climatic conditions, variability in climate parameters and extreme weather events. Combining these trends showed that while environmental conditions have ameliorated for some species, they have become more abiotically stressful for others (e.g. hygrophilous species). Concurrent with changes in the island’s climate, there have been rapid changes in the elevational distribution of Marion Island’s native vascular flora. On average species ranges expanded upslope (as predicted in response to the warming experienced on the island), although individual range expansion rates varied greatly. As a result of the idiosyncratic expansion rates, altitudinal patterns of species richness and community composition changed considerably. Therefore, both speciesand community-level changes occurred in the flora of Marion Island, demonstrating the community’s sensitivity to climate change. To determine the potential for interspecific interactions to have mediated these changes in species elevational ranges, spatial variation in the balance of positive and negative plant-plant interactions were examined. Increasing spatial association between four dominant species along an altitudinal severity gradient suggested that the intensity of facilitation, relative to the intensity of competition, is greater under more severe conditions. While, interaction strength varied between species pairs, the nature of relationship was consistent across the species. At a broader spatial scale, the performance of the grass Agrostis magellanica was compared in the presence and in the absence of the cushion plant Azorella selago along the entire altitudinal range of both species. The influence of the cushion plant on A. magellanica switched from negative to positive with increasing environmental severity, reaching a positive asymptote under extreme environmental conditions. Therefore, on Marion Island the spatial variation in the nature of biotic interactions is related to environmental severity, and facilitative interactions can be strong under extreme environmental conditions. These results show that positive biotic interactions are important at higher elevations on Marion Island, and could thus accelerate upslope range expansions in response to climate change. Nonetheless, competitive inhibition of upslope species movement, especially in areas of dense vegetation (i.e. mid or low altitudes), could have the opposite result, acting antagonistically with the effect of rising temperatures. This research highlights the importance of considering interspecific interactions when examining the biotic implications of climate change, both for affecting the rate at which species ranges change and the extent of species distributions. / AFRIKAANSE OPSOMMING: Die verskuiwing van spesies se verspreidingspatrone is ‘n belangrike gevolg van klimaatsverandering en kan die samestelling, struktuur en funksionering van ekosisteme affekteer. Oor die algemeen, in reaksie op verwarming, kom spesies op hoër hoogtes bo seespieël en hoër breedtegrade voor, alhoewel daar groot verskille tussen spesies in hierdie aspek is. Behalwe vir klimatologiese faktore, is spesies se verspreidingslimiete ook sensitief vir biotiese interaksies met ander spesies. Daarom kan interaksies tussen spesies die effek van klimaatsverandering op spesiesverspreiding verder beïnvloed. In hierdie verhandeling word klimaatsverandering, verandering in verspreiding van spesies en geografiese variasie in plant-plant interaksies ondersoek. Dit word gedoen ten einde die moontlikheid te toets dat biotiese interaksies die verandering in verspreidingspatrone van klimaat gedrewe spesies op sub-Antarktiese Marion Eiland beïnvloed. Marion Eiland se klimaat het aansienlik tussen 1949 en 2003 verander, met betekenisvolle neigings in biologies-relevante parameters, insluitend gemiddelde klimaatstoestande, variasie in klimaat en uiterste weerstoestande. As die veranderinge saam beskou word, wys dit dat, terwyl omgewingstoestande vir sommige spesies verbeter het, toestande vir ander spesies abioties meer ongunstig geword het (bv. akwatiese plantsoorte). Tesame met die veranderinge in die eiland se klimaat, het die hoogte bo seespieël verspreiding van Marion Eiland se inheemse vaatplante vinnig verander. Gemiddeld het spesies-verspreiding se hoogte bo seespieël na hoër hoogtes verskuif (soos voorspel in reaksie op verwarming), alhoewel die tempo van verskuiwing na hoër hoogtes tussen spesies verskil het. As gevolg van hierdie idiosinkratiese reaksies, het die aantal en samestelling van plant spesies op verskillende hoogtes op die eiland aansienlik verander. Die sensitiwiteit van Marion Eiland se flora ten opsigte van klimaatsverandering word deur hierdie verandering gedemonstreer. Om te bepaal of die interaksies tussen spesies verspreidingspatrone kan beïnvloed, is die geografiese variasie in die balans van positiewe en negatiewe interaksies ondersoek. Vier dominante vaatplante het meer geassosieerd geraak hoe hoër hulle bo seespieël voorgekom het. Dit is ‘n aanduiding dat die sterkte van die positiewe interaksies (fasilitering), relatief tot die sterkte van die negatiewe reaksie (kompetisie), groter onder uiterste omgewingstoestande is. Die sterkte van die interaksie het verskil tussen spesies pare, maar die verhouding tussen omgewingstoestande en die sterkte van die interaksie was dieselfde vir alle spesies. Op ‘n breër geografiese vlak is die opbrengs van die gras Agrostis magellanica in die teenwoordigheid en afwesigheid van die polsterplant Azorella selago op alle hoogtes waar die plante saam voorkom vergelyk. Die invloed van A. selago op A. magellanica was negatief op lae hoogtes bo seespieël, maar het meer positief geraak met ‘n toename in hoogte bo seespieël, tesame met omgewingshardheid. Die invloed van die polsterplant op die gras het ‘n positiewe asimptoot onder uiterste omgewingstoestande bereik. Dus, op Marion Eiland is die geografiese variasie in biotiese interaksies verwant aan omgewingstoestande, en positiewe interaksies kan selfs onder die uiterste omgewingstoestande sterk wees. Hierdie resultate wys dat positiewe biotiese interaksies tussen plante belangrik is by hoër hoogtes bo seespieël op Marion Eiland. Die interaksies kan dus die opwaartse verspreiding van spesies in reaksie op klimaatsverandering versnel. Nogtans kan negatiewe interaksies die teenoorgestelde effek hê aangesien kompetisie tussen plante, veral in plekke met digte plantegroei (d.w.s. lae of middel hoogtes bo seespieël) opwaartse verskuiwing van spesies kan verhinder. Hierdie navorsing dui aan hoe belangrik dit is om interaksies tussen spesies in ag te neem, aangesien die interaksies die tempo en omvang van veranderinge in verspreiding kan beïnvloed.

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...

The requirements of true frogs on breeding sites were monitored at 19 locations in the Hradec Králové Region and the Central Bohemia Region and Vysočina Region. Specific sites were selected according to the high variability. Breeding sites are mutually different representation of true frogs, water volume, depth, water and surrounding vegetation. The data of oviposition three different species of czech frogs - moor frog (Rana arvalis), agile frog (Rana dalmatina) and common frog (Rana temporaria) - were collected in the spring months, from the end of March until the end of April, from 2012 to 2015. During this period were collected data from 927 egg clutches of these species. The data were obtained by non-invasive way - measuring of inividual clutches directly on the reproductive site. At each breeding site was also recorded the required parameters of the breeding pond and the surrounding environment (presence of true frogs, the water volume and depth of the pond, the presence and density of aquatic vegetation, surrounding vegetation, air and water temperature, pH value of water, etc.). The results presented in this work confirm that the three species of true frogs have, in some parameters, different standards to select of breeding sites. This clarification of species- specific claims is also...