Polar desert environments are limiting in plant available nutrients, mainly nitrogen (N) and phosphorus (P) that severely limit plant growth and establishment. Cryogenic activity regularly patterns the ground into a patchwork of frost boils – sorted circles that are associated with an increase in moisture, fertility and plant cover. Within some frost boils, the accumulation of ice-rich soil at the permafrost table can cause an upward flow of soil organic carbon (SOC) enriched permafrost material into the active layer. These diapiric intrusions are predicted to fuel microbial activity and enrich the horizon in N and P; however, the enrichment of the diapir horizon and accessibility by plants has yet to be studied. The aim of this research was to characterize the N distribution within diapir horizons located in frost boils and the effect of these intrusions on vascular plant N uptake in a polar desert ecosystem of the Canadian High Arctic. Natural abundance and enriched isotope 15N techniques were used to trace the flow of N through the soil-plant system. Surface and diapir horizons contained the highest total C and total N content within frost boils. Natural abundance δ15N analysis indicated that uptake by Salix arctica plants located on frost boils in the absence of a diapir horizon were sourcing N from the surface. However, when diapir nutrients became available, S. arctica plants began sourcing N from the diapir horizon and underlying low SOC sources in the soil, while reducing uptake from the surface. The altered foraging strategy of S. arctica in response to diapir horizon formation was further indicated by significant uptake of atom%15N nutrients that were injected directly into diapir horizons. These findings suggest diapir horizons are enriched in N and accessible by plants roots as an important nutrient source that is instrumental in their survival within frost boils of a polar desert ecosystem in the high arctic.

Papio ursinus are dietary generalists that exploit a diverse repertoire of food resources. This study explored the foraging strategies of a group of Papio ursinus and the foraging differences between subgroups classified by age and sex. Food resource preference, nutritional properties of food resources, and nutritional demands were examined to test the hypotheses that the foraging strategies exhibited by the subgroups would differ and that food selection is driven by nutritional demands. Adult females and juveniles were found to seek out food resources higher in proteins, while adult males were found to prefer food resources higher in carbohydrates. The findings support the alternative hypotheses and suggest that nutritional pressures are the best predictor of foraging optimization. A pilot study, involving the observation of a provisioned group of Macaca mulatta, that proved elemental to the formulation of the research design employed in the study of Papio ursinus, is also described.

Orientador: Elza Maria Guimarães Santos / Resumo: A limitação de pólen é um dos fatores que mais afeta a produção de frutos e sementes de muitas populações naturais. Cerca de 60% das angiospermas apresentam baixo sucesso reprodutivo decorrente da transferência ineficiente dos grãos de pólen pelos polinizadores. Assim, o objetivo geral desse estudo foi avaliar diversos aspectos ligados à limitação de pólen em Zeyheria montana (Bignoniaceae), uma espécie ornitófila e autoincompatível. Ao longo do período de florescimento, com ampla variação do anúncio floral, nós avaliamos o efeito do padrão de forrageamento dos polinizadores dentro e entre plantas sobre o sucesso reprodutivo das mesmas. Avaliamos também as estratégias de forrageamento empregadas por cada espécie de polinizador e o efeito do roubo de néctar sobre a produção de frutos. Além disso, estimamos o tamanho do genoma das plantas com a finalidade de avaliar se havia variações intrapopulacional no nível de ploidia que pudessem estar associadas ao baixo sucesso reprodutivo. Em geral, nós demonstramos que a baixa qualidade do pólen transferido pelos polinizadores é o principal fator limitante do sucesso reprodutivo de Z. montana. Esse efeito ocorre principalmente no pico do florescimento, quando o anúncio floral é mais intenso, e os polinizadores tendem visitar um maior número de flores sequenciais dentro da mesma planta transferindo pólen incompatível. Além disso, o padrão de movimento entre plantas também não se mostrou eficiente, visto que os polinizadores frequentemen... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pollen limitation is one of the factors that most affects the fruits and seeds production of many natural populations. Around 60% of angiosperms have low reproductive success due to inefficient pollen grains transfer among flowers by pollinators. Thus, the general goal of this study was to evaluate several aspects related to pollen limitation in Zeyheria montana (Bignoniaceae), an ornithophilous and self-incompatible species. Throughout the flowering period, with wide variation in floral display, we evaluated the effect of the pollinators’ foraging pattern within and between plants on their reproductive success. We also evaluated the foraging strategies employed by each pollinator species and the effect of nectar robbing on fruit production. In addition, we estimated the plants’ genome size in order to evaluate whether there were intrapopulation variations in the ploidy level that could be associated with the low reproductive success. In general, we demonstrated that the low pollen quality transferred by pollinators is the main limiting factor of the reproductive success. This effect occurs mainly at the flowering peak, when the floral display is more intense, and pollinators tend to visit a larger number of sequential flowers within the plant transferring incompatible pollen. In addition, the movement pattern between plants also was not efficient, since pollinators often visited nearby plants that possibly were more related. Although some hummingbirds species alternate their... (Complete abstract click electronic access below) / Doutor

Faire un choix n’est pas juste un évènement spontané. La recherche d’une ressource alimentaire, par exemple, implique un investissement temporel et est donc en conflit avec d’autres activités essentielles telles que la vigilance pour les prédateurs. Ainsi être sélectif augmente le risque de se faire attaquer par un prédateur. Par ailleurs, être sélectif implique aussi de rejeter beaucoup de potentielles options avant de finalement en accepter une et donc accepter une perte non négligeable d’opportunités en présence de potentiels compétiteurs. Pour ces raisons, une réduction du niveau de sélectivité est attendue chez un individu exposé à une situation de forte compétition ou à un fort risque de prédation. Les carabes évoluent au sein de communautés composées, pour la plupart, d’un nombre important de potentiels compétiteurs et prédateurs. Les connaissances actuelles en écologie comportementale et en écologie prévoient que le comportement d’approvisionnement alimentaire des coléoptères carabiques devrait varier en fonction des niveaux de risques de compétition et de prédation qu’ils rencontrent et donc de la composition des communautés dans lesquelles ils se trouvent. Dans cette thèse, nous avons mesuré les changements de sélectivité alimentaire de deux espèces de carabes en présence de signaux de prédateurs ou de compétiteurs. A l’aide d’expériences de laboratoire effectuées à différentes échelles spatio-temporelle, nous avons réussi à montrer que la sélectivité alimentaire d’un carabe granivore Harpalus affinis peut varier en fonction du contexte dans lequel il cherche sa nourriture et être diminuée en présence de prédateurs. Par ailleurs le sexe des individus, l’espèce de graine qui leur est proposée et l’intensité du risque auquel ils sont confrontés semblent aussi avoir un effet sur la variation de sélectivité des individus. Aucun lien n’a cependant été trouvé entre le statut immunitaire ou la personnalité des individus et leur niveau de sélectivité alimentaire. Testé dans des conditions similaires, le carabe omnivore Poecilus cupreus, quant à lui, ne fait pas varier sa sélectivité pour les ressources testées. S’ils sont extrapolables ces résultats pourraient servir à expliquer la grande variabilité des taux de prédation de graines au champ par les carabes rapportés dans les différentes études. Ces résultats pourraient permettre aussi d’expliquer la difficulté d’extrapolation existante entre les taux de prédation de graines mesurés en laboratoire et les résultats obtenus au champ. Globalement, cette thèse confirme qu’une meilleure compréhension du processus de prise de décision chez les carabes est essentielle pour évaluer leur efficacité en tant que potentiels auxiliaires de cultures. / Making a choice requires, implicitly, an investment of time in one behaviour at the expense of an investment in another. Being choosy would increase the risk of losing many food item opportunities to competitors, and is directly in conflict with other essential tasks such as predator avoidance. Individuals are thus expected to adjust their level of choosiness in response to the competition and predation context. The available behavioural ecological theory and the empirical ecology of carabids would suggest that competition and predation interference induces changes in the foraging behaviour of carabid individuals. Carabids typically operate within communities in which competition and predatory interference interactions occur and are ever present; there are high levels of intraguild interference. A better understanding of how risks of these two interference interactions modify individual decision making for prey would therefore help to improve the biocontrol of weeds by communities of carabids. This thesis focused on how changes in level of choosiness occur when individual carabids forage under intraguild interference. Using laboratory experiments, done at different spatio-temporal scales, we demonstrate that the decision-making processes of foraging carabids might differ between contexts, between species and between individuals. Our focal species, the granivore Harpalus affinis, was found to reduce its level of choosiness while foraging under intraguild interference. In doing so H. affinis individuals increased their overall rate of seed acceptance. This change in choosiness was dependant on the intensity of the risk, the seed species offered in test and the sex of individuals. We found no link between individual levels of choosiness and either immunity or personality traits. When tested under similar conditions, individuals of the omnivorous carabid Poecilus cupreus did not change their level of choosiness for seeds. These findings would help explain the high variability in seed predation rates observed between studies conducted in-field, and the differences observed between laboratory studies and fields measurements in carabids. Globally, this thesis has confirmed that a deeper understanding of the decision making process of carabids seed-eating species is requires to evaluate their choice of prey and assess their relevance as biological control agents in the wild.

As formigas se adaptam as diferentes situações que encontram no seu ambiente em parte por apresentarem flexibilidade comportamental. Um exemplo é o uso de mais de uma estratégia durante a exploração de um recurso alimentar. No caso da Ponerinae Pachycondyla striata, as formigas podem forragear solitariamente ou fazer recrutamento por tandem running. Apesar desta espécie estar presente em diversas áreas verdes em ambiente urbano, pouco se sabe sobre o seu comportamento durante o forrageamento nessas áreas. Por isso, o objetivo deste trabalho foi analisar as estratégias de forrageamento e os comportamentos de P. striata em ambiente urbano. O estudo foi realizado em um jardim da Cidade Universitária (USP, campus Butantã). No local foram observadas 96 formigas de 12 colônias. Como iscas alimentares foram usadas proteína (atum) e carboidrato (maçã com mel) em duas quantidades (3g e 7g) e em duas distâncias do ninho (0,5 m e 4,0 m). Durante 90 minutos foram registrados: as estratégias de forrageamento; os comportamentos das forrageadoras; as interações com espécies competidoras; o tempo de trajeto entre o ninho e a isca. Verificou-se que o forrageamento solitário foi a principal estratégia, sendo utilizada por todas as forrageadoras e que a atividade solitária aumentava quando o alimento próximo ao ninho era proteína. O recrutamento foi realizado por 81% das forrageadoras, mas as formigas perderam o contato em 27% dos recrutamentos. As chances de uma forrageadora recrutar eram maiores em três situações: quando o alimento era proteína; estava perto do ninho; e a umidade do ar era alta (70% UR). Cerca de 72% das forrageadoras tiveram competição nas iscas, sendo a competição interespecífica mais frequente que a intraespecífica. Durante as interações com as competidoras, as forrageadoras apresentaram, principalmente, comportamento agressivo. Quanto ao tempo de trajeto, o forrageamento solitário era percorrido em menos tempo que o recrutamento, independente da distância. Por fim, verificou-se uma correlação negativa entre a ordem das viagens e o tempo do trajeto em ambas as distâncias e estratégias de forrageamento. Conclui-se que os dados coletados neste trabalho reforçam a prevalência do forrageamento solitário como principal estratégia da espécie e também trazem novas informações, como a tomada de decisão baseada no tipo do alimento, a variação na atividade de forrageamento devido a fatores abióticos, as interações competitivas no ambiente urbano e o aprendizado individual e social entre as forrageadoras / The ants adapt to different environmental contexts exhibiting behavioral flexibility. An example of behavioral flexibility is the use of more than one foraging strategy. In the case of Ponerinae Pachycondyla striata, the ants can forage solitarily or recruit and guide nestmates to a food sorce by tandem running. This species is found in various green areas in urban environment, but little is known about its foraging behaviour in this area. The aim of this research was to analyze the foraging strategies and the behaviors of P. striata in urban environment. The study was performed in a garden of the University City (USP campus Butantã). At this site we observed 96 ants of 12 colonies. As feeding baits were used protein (tuna) and carbohydrate (apple with honey) in two quantities (3g and 7g) and at two distances from the nest (0,5m and 4,0m). During 90 minutes we registered: the foraging strategies; the behaviors of the foragers; the interactions with competing species; and the travel time from the nest to the bait. It was found that the solitary foraging was the main strategy used by all the foragers. The solitary foraging activity was especially frequent when protein was close to the nest. The recruitment was performed by 81% of the foragers, but the ants lost contact in 27% of the recruitments. The frequency of recruitment increased in three foraging contexts: when the food was protein; was close to the nest; and with high air humidity (70% UR). About 72% of the foragers found competitors at the baits, and interspecific competition was more frequent than intraspecific competition. The foragers presented during the interactions with the competitors, mainly, aggressive behavior. Traveling time during solitary foraging foraging went through in less time that recruitment, regardless the distance. Lastly, it was verified a negative correlation between the traveling order and the traveling time at both distances and foraging strategies. Our data lead us to conclude that the solitary foraging is the main strategy of P. striata, adding new information as the decision making based on food characteristics, the variation in foraging activity due to abiotic factors and the competing interactions in urban environment and individual and social learning between ants

Birds are a major pest in vineyards both in New Zealand and overseas. There is a need for new behavioural research on birds' foraging habits and feeding preferences in vineyards, as much of the literature to date is anecdotal. Research on cues to birds' feeding will provide a basis on which new deterrent and control strategies can be devised. Spatial-and temporal bird damage in a small vineyard block was mapped to find if damage was correlated with grape maturity and environmental factors. Vineyard and field observations of bird behaviour using video technology combined with preference experiments aimed to establish the relative roles of grape sugar concentration and colour in avian selection. Proximity of vineyards to bird roosts affects damage levels, regardless of differing maturity between locations. The rate of damage tends to increase exponentially once grape maturity has passed a threshold of 13 °Brix. Bunches positioned closest to the ground receive more damage if blackbirds or song thrushes are the predominant pests. Both sugar concentration and grape colour were found to affect birds' feeding preference, but the importance of the two factors varied between years. Black and green grape varieties were differentially preferred by blackbirds (Turdus merula) and song thrushes (Turdus philomelos) while silvereyes (Zosterops lateralis) appeared to have no strong colour preference. It was apparent that there were other, not assessed, grape factors that also affect selection. In small unprotected vineyards that are adjacent to bird roosts the entire grape crop can be taken by bird pests. Besides removing the roosts, which can be beneficial shelterbelts in regions exposed to high winds, growers currently may have no alternative other than to use exclusion netting to keep crops intact. The differential preferences between bird species for variety characteristics suggest that any new deterrents and other strategies to deflect birds from grape crops may need to be species-specific.

No description available.

It is generally accepted that the Marginal Value Theorem (MVT) describes optimal foraging strategies. Some research findings, however, indicate that in natural conditions foragers not always behave according to the MVT. To address this inconsistency, in a series of computer simulations, I examined the behaviour of four types of foragers having specific foraging efficiencies and using the MVT and alternative strategies in 16 simulated landscapes in an ideal environment (no intra- and inter-species interactions). I used data on elk (Cervus elaphus) to construct the virtual forager. Contrary to the widely accepted understanding of the MVT, I found that in environments with the same average patch quality and varying average travel times between patches, patch residence times of some foragers were not affected by travel times. I propose a mechanism responsible for this observation and formulate the perfect forager theorem (PFT). I also introduce the concepts of a foraging coefficient (F) and foragers hub (), and formulate a model to describe the relationship between the perfect forager and other forager types. I identify situations where a forager aiming to choose an optimal foraging strategy and maximize its cumulative consumption should not follow the MVT. I describe these situations in a form of a mathematical model. I also demonstrate that the lack of biological realism and environmental noise are not required to explain the deviations from the MVT observed in field research, and explain the importance of scale in optimal foraging behaviour. I also demonstrate that smart foraging, which is a set of rules based on key ecological concepts: the functional response curve (FRC), satisficing, the MVT, and incorporates time limitations, should allow for fitness maximization. Thus, it should be an optimal behavior in the context of natural selection. I also demonstrate the importance of the FRC as a driver for foraging behaviors and argue that animals should focus more on increasing the slope of their FRC than on choosing a specific foraging strategy. Natural selection should, therefore, favor foragers with steep FRC. My findings introduce new concepts in behavioural ecology, have implications for animal ecology and inform wildlife management.

The Eurasian spruce bark beetle Dendroctonus micans is a major pest of spruce which is expanding its range in France, Turkey, England and Wales. Its monospecific predator Rhizophagus grandis has followed naturally the bark beetle into most areas and, since the 1960s, has also been mass-produced and successfully released within newly infested locations. In this scope, the development of an effective trapping method would be very useful to assess the bark-beetle presence at previously uninfested sites, or predator establishment after release or natural spread. We demonstrated the efficiency of oxygenated monoterpenes-baited kairomone traps to monitor R. grandis in various epidemiological conditions, including areas localized behind or at the limit of the pest’s distribution, or in areas where artificial releases were performed. Because the predator is strictly species-specific, another exciting possibility offered by the kairomone trapping is the indirect monitoring of the pest itself in areas of unknown status (e.g. areas under colonization, or considered as at risk at medium- term). R. grandis is also considered as one of the most valuable natural enemies to strike aggressive North-American Dendroctonus species. In this respect, R. grandis has been recently applied in a neo-classical biological program against the red turpentine beetle D. valens, which invaded China from North America in the late 1990’s. In laboratory tests conducted on pine logs in the laboratory, or on living pine trees in the field, we demonstrated that R. grandis adults can successfully enter and reproduce into D. valens galleries. In Europe, R. grandis is the only species regularly found in the brood systems of D. micans, where adults and larvae attack the gregarious larvae of their prey. In such enclosed systems, R. grandis’ functional response is therefore influenced by various interrelated components, such as the prey density, the predator density, or the prey distribution. Measuring the predator’s success in terms of larval survival and growth rates, we demonstrated the time spent by R. grandis larvae to wound and kill their prey to be the main factor limiting their development. This factor may be considerably influenced by the proportions of diseased, wounded or molting prey rise in the brood system, for instance as a result of an increase in prey density, or due to the presence of conspecific adults (which wound their prey but do not consume them entirely). Furthermore, our tests suggest that no cannibalism or noticeable intraspecific competition occurred between R. grandis larvae, whereas some lighter mode of competition probably took place. R. grandis also exhibits a reproductive numerical response to prey density, which mainly relies on the perception of chemical stimuli and inhibitors released in the bark beetle brood system. In the current study, we developed a non-destructive approach to follow the dynamics of volatile compound production, using sequential sample collection on SPME fibers. Our tests demonstrated that the larval activity of D. micans or D. valens strongly influences the release of some oxygenated monoterpenes. However, our attempts to correlate the relative quantities of some identified chemicals to offspring production were less successful as it concerns the identification of potential oviposition stimuli and inhibitors. The problematic rose by the progression of D. micans, as well as detailed results of each of the described above studies are discussed in the two published papers and the three manuscripts forming this thesis. Bringing all these studies together, several perspectives are also presented in the general discussion. / Ravageur des épicéas, Dendroctonus micans est toujours en voie d’extension en France, en Turquie, en Angleterre et au Pays de Galles. Dans la plupart de ces zones, le dendroctone est accompagné de manière naturelle par son prédateur monospécifique, Rhizophagus grandis. Depuis les années 1960, le prédateur a également fait l’objet d’une production de masse et de programmes de lâchers dans les zones d’arrivée récente du scolyte. Dans le cadre de la lutte biologique contre D. micans, les gestionnaires forestiers doivent donc estimer au plus tôt la présence du ravageur dans des zones jusque là indemnes, mais également vérifier l’établissement du prédateur par progression naturelle ou résultant d’introductions délibérées. Dans la présente étude, nous avons démontré l’efficacité de pièges d’interception appatés à l’aide de monoterpènes oxygénés pour la capture de R. grandis. Celle-ci s’est faite dans différentes conditions épidémiologiques, incluant notamment des zones situées en arrière du front de progression du scolyte et des zones où des lâchers artificiels ont été réalisés. Comme R. grandis est strictement inféodé au dendroctone, un autre avantage de la technique est la possibilité de réaliser un dépistage indirect du ravageur dans les zones où son statut est incertain (zones en cours de colonisation, ou considérées comme à risque à moyen terme). Par ailleurs, R. grandis est également considéré comme un des meilleurs ennemis naturels potentiels pour lutter contre d’autres espèces de Dendroctonus aggressifs. Dans cette optique, R. grandis a été récemment utilisé dans un programme de lute biologique contre D. valens, ravageur invasif arrivé en Chine dans la fin des années 1990 en provenance d’Amérique du Nord. Nous avons démontré la capacité de R. grandis à s’introduire et à se reproduire dans les galeries de D. valens lors de tests de laboratoire, mais aussi sur des arbres vivants en pinèdes. En Europe, R. grandis est strictement inféodé aux galeries de D. micans, où larves et adultes du prédateur s’attaquent aux larves grégaires du scolyte. Dans ce système clos, la réponse fonctionelle de R. grandis est influencée par plusieurs facteurs étroitement corrélés, la densité de proies, la densité de prédateurs, et la distribution des proies. En mesurant l’efficacité de prédation de R. grandis en termes de survie des larves et de taux de croissance, nous avons démontré l’influence sur leur développement du temps passé par les larves à blesser et à tuer leurs proies. Ce facteur est par ailleurs fortement dépendant de la proportion de larves malades, blessées ou en cours de mue au sein du système ; une proportion qui peut augmenter en réponse à une augmentation de la densité de proies, ou lorsque des adultes sont présents (ceux-ci blessent les proies mais ne les consomment pas entièrement). Enfin, nos tests suggèrent qu’il n’existe que peu de cannibalisme ou de compétition intraspécifique entre larves de R. grandis, tandis que des modes de compétition moins importants prennent vraisemblablement place. R. grandis présente également une réponse numérique reproductive à la densité de proies disponibles, principalement basée sur la perception de stimuli et d’inhibiteurs présents dans les galeries du scolyte. Par la collecte de composés volatils présents dans ces systèmes à l’aide de fibres SPME, nous avons développé une méthode non-destructive pour suivre la dynamique de production des médiateurs chimiques. Nos tests ont démontré que l’activité des larves de D. micans ou D. valens influence fortement la dynamique de production de certains monoterpènes oxygénés. En revanche, il n’a pas été été possible de corréler les différents composés identifiés au nombre de larves de R. grandis présentes dans le système. La problématique soulevée par la progression de D. micans, de même que les résultats détaillés de chacune des études décrites ci-dessus sont discutés dans les deux papiers publiés et les trois manuscrits formant cette thèse. Les différentes perspectives apportées par ce travail sont également présentées dans la discussion générale.

A study was conducted to determine what impact high white-tailed deer (Odocoileus virginianus) densities were having on the native grasslands of a tallgrass: aspen forest tract embedded within an agro-urban setting. Due to excessive spring moisture, row-crops were unavailable the first year. Using microhistological fecal analysis to determine dietary composition, deer were assessed to be placing the site’s favoured native plant species at risk of extirpation. Measuring woody stem abundance and height along and near the prairie: forest ecotone, deer were found to restructure woody growth but not directly influence encroachment rates. Indirectly, however, deer facilitated forest encroachment and prairie degradation through seed dispersal, nitrogen deposition, gap-dynamics, and trampling. Comparing dietary composition to nutritional data, deer grazed to maximize fitness, selecting foods high in IVDMD, minimizing energy expenditure, and optimizing CP. High crop CP was offset by intensively grazing particular native plants. ADF was an effective nutritional marker, not AIA.