The first part is a study of an ecological model with one herbivore and $N$ plants. The system has a new type of functional response due to the speculation that the plants compete with each other and have different levels of toxin which inhibit the herbivore's ability to eat up to a certain amount. We first derive the model mathematically and then investigate, both analytically and numerically, the possible dynamics for this model, including the bifurcation and chaos. We also discuss the conditions under which all the species can coexist. The second part is a study in the normal form theory. In particular, we study the relations between the normal forms and the first integrals in analytic vector fields. We are able to generalize one of Poincare's classical results on the nonexistence of first integrals in an autonomous system. Then in the space of 2n-dimensional analytic autonomous systems with exactly n resonances and n functionally independent first integrals, we obtain some results related to the convergence and generic divergence of the normalizations. Lastly we give a new proof of the necessary and sufficient conditions for a planar Hamiltonian system to have an isochronous center.

Biologically-mediated subsurface remediation by biofilm communities is a poorly understood process that is spatially and temporally dynamic. Two microbial responses, catabolism and the stress response glutathione-gated potassium efflux (GGKE), to benzene, pentachlorophenol (PCP), or Cd exposure were studied in up-flow sand columns to examine the contribution of each response to the overall functional response of a subsurface biofilm. Benzene was catabolized in the aerobic zone, and did not activate the GGKE response, and exhibited the highest biomass concentrations of all columns. PCP was not catabolized during this study, but was found to elicit two responses, oxidative phosphorylation uncoupling and GGKE, that appeared to be concentration dependent. Oxidative uncoupling was the controlling metabolic response up to 10 mg/L PCP, while the GGKE stress response was activated near 20 mg/L PCP. PCP column biomass did not show long-term biomass detachment, although immediate detachment occurred during initial GGKE activation. Cd column biomass activated the GGKE response as perturbing Cd concentrations increased. Extracellular polymeric substance (EPS)-Cd complexation was a possible detoxification mechanism, as biomass concentrations did not decrease with increasing Cd concentration, and increased as Cd concentrations decreased. Results of this study suggested that the increased exposure of electrophilic contaminants to sand column biomass did not cause biomass detachment. / Master of Science

No description available.

Predation by cougars (Puma concolor) variously can structure ecosystems and preserve biodiversity, engender conflict where livestock and pets are killed, and even drive prey populations to extinction. Effective management requires a firm grasp of the ecological drivers of predation, but these remain poorly understood due to difficulty obtaining sufficient data. My objective was to test hypotheses about drivers of predation in a population of wild cougars foraging in a multi-prey system in west-central Alberta, Canada. To obtain necessary data, I began by refining Global Positioning System (GPS) telemetry cluster techniques to monitor predation. I found that models alone were insufficient and that field visitation was required to estimate kill rate and prey composition accurately, but logistic regression models could direct field-work to improve efficiency, permitting continuous monitoring of cougar predation and generating large sample sizes. I assessed the role of scavenging as a foraging strategy and found that cougars scavenged opportunistically, reducing predation when carrion availability was high. Scavenging also made cougars susceptible to incidental snaring at wolf bait stations, and survival analysis revealed important consequences for cougar population trajectory and harvest management. I evaluated competing hypotheses about the magnitude of cougar predation and the influence of season and prey vulnerability on kill rate and prey composition. Cougars were effective predators, killing ungulates at rates near the upper end of the previously reported range. Cougar kill-rate increased by a factor of 1.5 in summer and cougars shifted prey composition seasonally as predicted by the juvenile and reproductive vulnerability hypotheses. Analysis of a multi-species functional response (MSFR) revealed that cougar impact on small populations of endangered prey is reduced by a tendency towards prey-switching but can be aggravated by the presence of individual specialists. Contrary to expectation, cougar MSFR was not driven by prey density, but rather by cougar demography and relative abundance of various prey. Finally, I reject the notion that cougars are nocturnal ambush predators, demonstrating instead that they hunt actively and make kills frequently during the day, exhibiting activity patterns loosely tied to those of their prey. I discuss the application of my findings for management and conservation. / Ecology

Understanding and predicting the way in which species interactions may change under the uncertain climatic future is imperative if the management of important resources is to be successful. Consumer – resource interactions underlie population dynamics and distribution, yet there is little known about how these interactions will respond to increasing temperature. Temperature increase can facilitate the movement and settlement of alien species into new ranges. Introduced species can often be ecologically damaging and unpredictable due to novel predator-prey interactions. Comparative functional response analysis has been used to gain insight into resource dependent behaviour and population dynamics. This study is an assessment of the way in which predicted temperature changes can affect resource consumption in three predators. The red lionfish Pterois volitans (Linnaeus, 1758) is a successful and hugely damaging invader in the Western Atlantic and sources point to an ongoing Mediterranean invasion. Through a series of laboratory experiments I assessed how temperature, habitat complexity, and light wavelength affect the functional response of lionfish towards a crustacean prey. I establish that lionfish have a persistent Type II functional response and that lower temperature decreased the magnitude of the functional response, suggesting that movement into the comparatively colder waters of the Mediterranean and British Isles could reduce the per capita response. Further, I found that red light reduced the maximum feeding rate of lionfish, compared to blue and white light, by dampening the attack rate. I assessed how temperature increase affects the proportional consumption of an amphipod prey by an intertidal predator, the bleniid, Lipophrys pholis (Linnaeus, 1758). Functional response analysis revealed that the shanny has a hump shaped relationship with increasing temperature wherein maximum feeding rate decreased at the highest temperature. Two prey supply models, where prey density was allowed to deplete, and where prey were replaced after consumption were compared and found to have differential results due to model choice. I used gut content data to assess the abundance, prey selection, degree of dietary overlap, in a commercial predator, cod (Gadhus morhua; Linnaeus, 1758) and a non-commercial predator, dogfish (Sycliorhinus canicula; Linnaeus, 1758) with regards to substrate type. While there were no significant conclusions to be made about habitat use, I found significantly larger populations of S. canicula and higher consumption of commercial invertebrates by S. canicula. I vi used this field data to inform further experiments, having highlighted S. canicula as a potential threat to commercial fisheries. A two-by-two experimental design was used to understand how differential acclimation of predator (S. canicula) and amphipod prey species (Echinogammarus marinus; Leach, 1815) affects the functional response of the predator. Increasing temperature concomitantly increased the magnitude functional response of S. canicula, however raised temperature caused a shift in functional response type, from Type II to Type III, conferring low prey density protection. Handling time was shorter when both predator and prey were acclimated to the raised temperature and as a result there was a significant interaction effect where maximum feeding rate was significantly higher when both predator and prey were acclimated. This increase in predation impact by S. canicula has the potential to affect valuable fisheries stocks due to the increasing populations of Scyliorhinus canicula and the additive effects of acclimation to raised temperature. Having highlighted the differential ways in which temperature can affect the per capita response of consumers I postulate a new metric wherein “Relative Impact Potential” of a consumer can be predicted under a set of environmental variables. This metric takes into account the per capita response, numerical response, and the potential change in predator and prey populations under the proposed conditions. I suggest the use of this metric as a rapid way of assessing and predicting potential threats to sustainability of fisheries under predicted climatic change. Overall, this thesis identifies species and scenarios wherein sustainability of important fisheries could be threatened. While this work focuses mainly on thermal responses, it demonstrates: (i) the utility of functional response analysis in assessing relative change in ecological impact under climate change scenarios; (ii) the species specificity of thermal responses and provides empiricle evidence of a hump shaped thermal response; (iii) the importance of considering both predator and prey when assessing ecological change, with reference to acclimation and population dynamics; and (iv) a metric with which to assess potential threats and ecological impact in a way that is standardized and easily accessible by managers and stakeholders alike.

Hemlock woolly adelgid, Adelges tsugae Annand, is an invasive pest threatening eastern (Tsuga canadensis (L.) Carrière) and Carolina hemlock (T. caroliniana Englem.) forests in the eastern US. A new predator, Laricobius osakensis Montgomery and Shiyake, has been found in association with A. tsugae in Japan. Laricobius osakensis was evaluated in a series of pre-release studies to assess its potential as a biological control agent for A. tsugae. Host-range studies indicated that L. osakensis is a specific predator that feeds predominantly and reproduces only on A. tsugae. The functional response "prey consumption changes in response to changes in prey density" was similar for both L. osakensis and Laricobius nigrinus Fender adults. However, L. osakensis had a higher numerical response"changes in oviposition in response to changes in prey density"than L. nigrinus. Laricobius osakensis larvae had a higher functional response than L. nigrinus larvae. Laricobius osakensis\' higher numerical and functional response indicates that this species can potentially be more effective than L. nigrinus. In the evaluation of L. osakensis in sleeve cages in the field from December to April high rates of adult survival, feeding, and reproduction were found. A pair of predators in a cage killed on average five adelgids/day. Peak oviposition occurred in March and April. Larvae from eggs placed in the cages reached maturity in 28-50 days, depending on the season, and only 6.7 % died before reaching maturity. Laricobius osakensis was able to survive, feed, develop, and reproduce in USDA cold-hardiness zones 5b and 6a of southwest Virginia. Behavior of L. osakensis and L. nigrinus was qualitatively similar but varied quantitatively. Laricobius osakensis was more active and had a lower association with T. canadensis. Interactions between species were minimal and not detrimental to either. Intrasexual copulation attempts were observed between males and to a lesser extent between females; however, intrasexual interactions were less frequent than intersexual interactions between the two species. Otherwise activity, including oviposition, was not altered by the presence of the other species. These studies indicate that L. osakensis has the potential to be a valuable addition to the natural enemies complex against A. tsugae. / Ph. D.

No description available.

Nesta tese investigaram-se relações de causa-efeito em curto prazo entre a estrutura do pasto e parâmetros do comportamento ingestivo de bovinos. Criaram-se contrastes de estruturas de pasto com uma espécie temperada e outra tropical e métodos de pastoreio (contínuo e rotativo). Os experimentos com Cynodon sp. cv. Tifton 85 (1 e 2) foram conduzidos entre janeiro e março de 2011. Os com Avena strigosa cv. Iapar 61 (3 e 4), entre julho e setembro de 2011. A altura de pasto que proporcionou a máxima taxa de ingestão (TI) no pastoreio contínuo foi considerada como altura pré-pastejo nos Experimentos 2 e 4, que simulavam o pastoreio rotativo. A esta altura impôs-se níveis de rebaixamento de 20; 40; 60 e 80%. O delineamento utilizado em todos os experimentos foi o de blocos completos casualizados com quatro repetições. O consumo foi estimado pela técnica da dupla pesagem. Os animais foram equipados com aparelhos registradores de movimentos mandibulares. As máximas TI foram observadas em 20 cm em Cynodon sp. e em 30 cm em A. strigosa. Animais não gastaram tempo adicional para tomar um bocado de equivalente massa no pasto alto em relação ao pasto baixo. No pastoreio rotativo a TI, manteve-se constante, até que 31 e 18% da altura inicial fossem removidos da pastagem alta e baixa, respectivamente. A A. strigosa permitiu maior TI potencial. Os animais gastaram mais tempo por bocado para consumir uma equivalente massa de bocado em Cynodon sp. em relação à A. strigosa, em ambos os métodos de pastoreio. / This thesis investigated cause-effect relationships between sward structure and short-term ingestive behavior of cattle. Contrasting sward structures were created with one temperate and one tropical species combined with two grazing methods (continuous and rotational). The experiments with Cynodon sp. cv. Tifton 85 (1 and 2) were carried out between January and March 2011. Those with Avena strigosa cv. Iapar 61 (3 and 4) took place between July and September 2011. The sward height that provided the highest short-term intake rate in continuous grazing, was regarded as pre-grazing in Experiments 2 and 4, which simulated rotational grazing. For this sward height, four intensities of herbage removal by grazing were imposed, namely 20, 40, 60 and 80%. A randomized complete block design was used in all experiments with four replicates. Intake was estimated by the double-sampling technique. Animals were equipped with IGER behavior recorder. The maximum short-term intake rates were observed at 20 cm for Cynodon sp. and 30 cm for A. strigosa. There was no difference in time required for a single bite between short and tall pastures. Under rotational grazing, intake rate was constant until 31 and 18% of the original tall and short sward heights were removed, respectively. A. strigosa was conducive to a higher short-term intake rate. Animals spent longer time per bite to ingest equivalent masses of Cynodon sp. in comparison to A. strigosa in both grazing methods.

No description available.

The pelagic zone of lakes is defined as the water column over the area of the lake benthos that does not receive enough light from the sun to allow macrophytes to grow. The four chapters of this thesis explore the spatial ecology of predator-prey interactions between schooling fish and their fish predators in this featureless environment. We first developed novel hydroacoustics methods to study fish and fish school swimming behaviour in the pelagic zone (Chapter 1 and 2). Then we characterized our in-situ school formation and prey movement observations using an ideal gas model to better understand the mechanisms that lead to fish and school densities during the daytime (Chapter 2 and 3). With this model we estimated the functional relationship between the schooling prey densities and predator encounter rates, and verified with empirical data a counterintuitive relationship that encounter rates decreased as overall prey densities increased (Chapter 3). The encounter rates suggested that predation within the pelagic zone might be greatly influenced by external forces if they provide spatial structure which encourages greater degrees of prey aggregation in predictable locations. In this regard we examined the predator-prey dynamics under wind and found large redistributions of prey and predators under windy conditions leading to greater aggregations in downwind locations. Further, we found that our study fish were larger in lakes that were oriented into the wind, perhaps demonstrating a benefit to fish growth under windy conditions (Chapter 4).