Whether species interactions are static or change over time has wide-reaching ecological and evolutionary consequences. However, species interaction networks are typically constructed from temporally aggregated interaction data, thereby implicitly assuming that interactions are fixed. This approach has advanced our understanding of communities, but it obscures the timescale at which interactions form (or dissolve) and the drivers and consequences of such dynamics. We address this knowledge gap by quantifying the within-season turnover of plant-pollinator interactions from weekly censuses across 3years in a subalpine ecosystem. Week-to-week turnover of interactions (1) was high, (2) followed a consistent seasonal progression in all years of study and (3) was dominated by interaction rewiring (the reassembly of interactions among species). Simulation models revealed that species' phenologies and relative abundances constrained both total interaction turnover and rewiring. Our findings reveal the diversity of species interactions that may be missed when the temporal dynamics of networks are ignored.

Le délestage de calcul ou de code est une technique qui permet à un appareil mobile avec une contrainte de ressources d'exécuter à distance, entièrement ou partiellement, une application intensive en calcul dans un environnement Cloud avec des ressources suffisantes. Le délestage de code est effectué principalement pour économiser de l'énergie, améliorer les performances, ou en raison de l'incapacité des appareils mobiles à traiter des calculs intensifs. Plusieurs approches et systèmes ont été proposés pour délester du code dans le Cloud tels que CloneCloud, MAUI et Cyber Foraging. La plupart de ces systèmes offrent une solution complète qui traite différents objectifs. Bien que ces systèmes présentent en général de bonnes performances, un problème commun entre eux est qu'ils ne sont pas adaptés aux applications temps réel telles que les jeux vidéo, la réalité augmentée et la réalité virtuelle, qui nécessitent un traitement particulier. Le délestage de code a connu un récent engouement avec l'avènement du MEC et son évolution vers le edge à multiple accès qui élargit son applicabilité à des réseaux hétérogènes comprenant le WiFi et les technologies d'accès fixe. Combiné avec l'accès mobile 5G, une pléthore de nouveaux services mobiles apparaîtront, notamment des service type URLLC et eV2X. De tels types de services nécessitent une faible latence pour accéder aux données et des capacités de ressources suffisantes pour les exécuter. Pour mieux trouver sa position dans une architecture 5G et entre les services 5G proposés, le délestage de code doit surmonter plusieurs défis; la latence réseau élevée, hétérogénéité des ressources, interopérabilité des applications et leur portabilité, la consommation d'énergie, la sécurité, et la mobilité, pour citer quelques uns. Dans cette thèse, nous étudions le paradigme du délestage de code pour des applications a temps réel, par exemple; les jeux vidéo sur équipements mobiles et le traitement d'images. L'accent sera mis sur la latence réseau, la consommation de ressources, et les performances accomplies. Les contributions de la thèse sont organisées sous les axes suivants : Étudier le comportement des moteurs de jeu sur différentes plateformes en termes de consommation de ressources (CPU / GPU) par image et par module de jeu ; Étudier la possibilité de distribuer les modules du moteur de jeu en fonction de la consommation de ressources, de la latence réseau, et de la dépendance du code ; Proposer une stratégie de déploiement pour les fournisseurs de jeux dans le Cloud, afin de mieux exploiter les ressources, en fonction de la demande variable en ressource par des moteurs de jeu et de la QoE du joueur ; Proposer une solution de délestage statique de code pour les moteurs de jeu en divisant la scène 3D en différents objets du jeu. Certains de ces objets sont distribués en fonction de la consommation de ressources, de la latence réseau et de la dépendance du code ; Proposer une solution de délestage dynamique de code pour les moteurs de jeu basée sur une heuristique qui calcule pour chaque objet du jeu, le gain du délestage. En fonction de ce gain, un objet peut être distribué ou non ; Proposer une nouvelle approche pour le délestage de code vers le MEC en déployant une application sur la bordure du réseau (edge) responsable de la décision de délestage au niveau du terminal et proposer deux algorithmes pour prendre la meilleure décision concernant les tâches à distribuer entre le terminal et le serveur hébergé dans le MEC. / Computation offloading is a technique that allows resource-constrained mobile devices to fully or partially offload a computation-intensive application to a resourceful Cloud environment. Computation offloading is performed mostly to save energy, improve performance, or due to the inability of mobile devices to process a computation heavy task. There have been a numerous approaches and systems on offloading tasks in the classical Mobile Cloud Computing (MCC) environments such as, CloneCloud, MAUI, and Cyber Foraging. Most of these systems are offering a complete solution that deal with different objectives. Although these systems present in general good performance, one common issue between them is that they are not adapted to real-time applications such as mobile gaming, augmented reality, and virtual reality, which need a particular treatment. Computation offloading is widely promoted especially with the advent of Mobile Edge Computing (MEC) and its evolution toward Multi-access Edge Computing which broaden its applicability to heterogeneous networks including WiFi and fixed access technologies. Combined with 5G mobile access, a plethora of novel mobile services will appear that include Ultra-Reliable Low-latency Communications (URLLC) and enhanced Vehicle-toeverything (eV2X). Such type of services requires low latency to access data and high resource capabilities to compute their behaviour. To better find its position inside a 5G architecture and between the offered 5G services, computation offloading needs to overcome several challenges; the high network latency, resources heterogeneity, applications interoperability and portability, offloading frameworks overhead, power consumption, security, and mobility, to name a few. In this thesis, we study the computation offloading paradigm for real-time applications including mobile gaming and image processing. The focus will be on the network latency, resource consumption, and accomplished performance. The contributions of the thesis are organized on the following axes : Study game engines behaviour on different platforms regarding resource consumption (CPU/GPU) per frame and per game module; study the possibility to offload game engine modules based on resource consumption, network latency, and code dependency ; propose a deployment strategy for Cloud gaming providers to better exploit their resources based on the variability of the resource demand of game engines and the QoE ; propose a static computation offloading-based solution for game engines by splitting 3D world scene into different game objects. Some of these objects are offloaded based on resource consumption, network latency, and code dependency ; propose a dynamic offloading solution for game engines based on an heuristic that compute for each game object, the offloading gain. Based on that gain, an object may be offloaded or not ; propose a novel approach to offload computation to MEC by deploying a mobile edge application that is responsible for driving the UE decision for offloading, as well as propose two algorithms to make best decision regarding offloading tasks on UE to a server hosted on the MEC.

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.

I characterized dusky dolphin (Lagenorhynchus obscurus) underwater bait-balling behaviors and acoustic signals, and compared data between Argentina and New Zealand (NZ) to investigate the roles of ecology versus social learning. I quantified prey herding and capturing behaviors from video footage, and I analyzed acoustic signals from narrowband recordings. In both locations, I related bait-balling behaviors and acoustic signals to group and prey ball sizes. In NZ, I also related dolphin behaviors to prey ball escape behaviors and acoustic signal parameters to examine proximate functions. Observed herding behaviors typically involved dolphins swimming around or under a prey ball using a side body orientation, while dolphins typically captured fish from the side of a prey ball using a ventral orientation. Coordinated prey-capture behaviors may have made it easier for dolphins to capture fish by trapping fish between dolphins. Signals were categorized as click trains, burst pulses, and combinations due to a bimodal inter-click interval distribution. I observed 3 whistle-like chirp-screams, but no whistles. Sequences of burst pulses also occurred that contained 2-14 burst pulses that aurally and visually appeared closely matched. Similarities between locations suggest that ecological context related to broad behavioral and acoustic parameters, while social learning differences may occur on a finer scale. In NZ, prey balls exhibited horizontal and vertical movements, but the only behavior that preceded escape was “funneling”, the brief formation of a ball shape where the height was at least twice the width. Dolphin behaviors that related to prey balls ascending were type of herding pass, location of prey-capture attempts, and body orientation during attempts. These behavioral parameters may also be used to counter vertical prey escape behaviors. In NZ, all signal categories had a direct or indirect role in capturing prey. Click train-burst pulses were likely used for echolocating on prey, burst pulses and sequences appeared to have communication roles, and the role of click trains was ambiguous. No signal categories appeared to have a herding function, but the sheer number of signals emitted may have caused fish to cluster together more tightly and therefore facilitated capture.

No description available.

Migratory behaviour of the Ya Ha Tinda (YHT) elk population is diminishing while the number of residents remaining on the YHT winter range year-round is increasing. Previous research addressing the fitness consequences of each migratory strategy assumed there was no advantage to either segment when they shared the YHT winter range. In testing this assumption, I found no spatial segregation of migrant and resident home-ranges during winter. Both groups were exposed to similar forage resources and residents were exposed to higher night-time, but not day-time predation risk. Residents were better than migrants at reducing the foraging costs of vigilance and increased vigilance in areas of high wolf predation risk, but not near human activity because of habituation. Migrants were not habituated to humans and exhibited more constant vigilance regardless of spatial variations in risk. My results do not support the previous assumption. Instead, I found residents may be at an advantage on the winter range while forage is abundant and no snow is present. / Ecology

Master of Science / Department of Entomology / David C. Margolies / Yoonseong Park / Phytoseiulus persimilis (Acari: Phytoseiidae) is a specialist predator on tetranychid mites, especially on the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The foraging environment of the predatory mites consists of prey colonies distributed in patches within and among plants. Quantitative genetic studies have shown genetic variation in, and phenotypic correlations among, several foraging behaviors within populations of the predatory mite, P. persimilis. The correlations between patch location, patch residence, consumption and oviposition imply possible fitness trade-offs. We used molecular techniques to investigate genetic variation underlying the foraging behaviors. However, these genetic studies require a sufficiently large amount of DNA which was a limiting factor in our studies. Therefore, we developed a method for obtaining DNA from a single mite by using a chelex extraction followed by whole genome amplification. Whole genome amplification from a single mite provided us with a large quantity of high-quality DNA. We obtained more than a ten thousand-fold amplified DNA from a single mite using 0.01ng as template DNA. Sequence polymorphisms of P. persimilis were analyzed for nuclear DNA Inter Transcribed Spacers (ITS1 & ITS2) and for a mitochondrial 12S rRNA. The sequence comparisons among individuals identified a number of polymorphisms in the 12S sequences. The foraging gene (for) associated with rover-sitter behavioral strategies of Drosophila is known to have role in feeding behaviors of honeybee and other arthropods. We surmised that the same or a similar gene may be present in P. persimilis. Among the foraging behavior(s) exhibited by this predatory mite, we were particularly interested in resource/prey-dependent dispersal behavior. We isolated a partial sequence that is presumed to be the orthologue of the foraging (for) gene. We named the putative foraging gene as Ppfor (for Phytoseiulus persimilis foraging gene). We used a fragment of Ppfor gene as a molecular marker between populations and among individuals and, further, to help understand behavioral phenotypes.

Master of Science / Department of Entomology / David C. Margolies / James R. Nechols / The study of how extrinsic factors affect the foraging efficiency and behavior of predaceous arthropods like Phytoseiulus persimilis is important to understand their various processes of acquiring prey, mates, refuges, oviposition sites, and overcoming obstacles posed by the environment. Many intrinsic and extrinsic factors affect predator foraging efficiency and behavior. One of the most influential extrinsic factors may be the host plant on which herbivorous prey are found. Recent studies suggest that plant architecture plays an important role in tritrophic interactions. In this work, I studied the effects of cucumber plant architecture and prey distribution on the foraging efficiency (prey-finding time and prey-consumption rate) and behavior (time allocated between moving, resting and feeding) of P. persimilis. Plant architecture represented differences in leaf number and size; however, all plants had the same total surface area. Plants with 6 small leaves (ca. 82.98 square cm each) were considered as complex architecture, whereas plants with only 2 large leaves (ca. 240.60 square cm each) were considered as simple. The prey distributions were: prey patch on a single basal leaf (closest leaf to the soil) and prey patch on all leaves. The foraging efficiency was assessed by measuring prey-finding time and prey-consumption rate, whereas the behavior was assessed by conducting observational studies on specific foraging activities. When placed either on the top or at the base of the plant P. persimilis encountered prey more rapidly (interval 0-30 minute) on complex and simple plants with prey patches distributed on all leaves. Differences in prey density (number of prey per leaf) had no effect on the prey-finding time of P. persimilis. The predator consumed more eggs on complex plants with prey patches distributed on all leaves. Phytoseiulus perismilis tended to find prey patches more quickly as well as consume more eggs on leaves close to its release point. Furthermore, the predator was observed to lay more eggs on leaves where it had consumed higher number of prey eggs. The dimensions of individual parts of the plant e.g., stem, petiole and leaf, affected the time allocated by P. persimilis between searching, resting and feeding. The predatory mite spent more time foraging on the stems and petioles of the simple plants whereas on complex plants it spent more time foraging on the leaves.

Foraging forms the cornerstone of an animal’s life-history. An individual's foraging success shapes the demography and health of a population. Understanding key facets of maternal foraging behaviour are crucial to get a holistic picture of both regional and local environmental factors that drive foraging behaviour. This study aimed to measure the maternal foraging behaviour of a marine top predator, the Subantarctic fur seal (Arctocephalus tropicalis), from Marion Island (MI) over a range of spatial and temporal scales. Arctocephalus tropicalis females from MI have one of the longest duration foraging trips for the species. They are most similar to conspecifics at temperate Amsterdam Island, but differ considerably from those at subantarctic Îles Crozet and Macquarie Island. Hitherto, no diving data existed for MI females. I illustrate how their diving behaviour is more similar to individuals from Îles Crozet despite their differences in foraging trip parameters. Together with Îles Crozet, MI females have one of the deepest mean diving depths (34.5 ± 2.2 m , 45.2 ± 4.8 m summer and winter respectively) and longest dive durations (70.2 ± 3 s , 104.3 ± 7.8 s summer and winter respectively) for the species. In summer, females follow the diel vertical migration of their myctophid prey. Counter intuitively, during the winter, females performed short and shallow crepuscular dives, possibly foraging on different prey. Considering that these individuals dive in deep waters, this is most likely related to myctophids occupying lower depths in the water column during winter. At dusk and dawn they are inaccessible to diving fur seals. At-sea data from multiple foraging trips per female illustrated that females have both a colony- and individual preferred foraging direction which varied seasonally. Individuals travelled consistently in the same direction regionally, but locally appear to track prey in a heterogeneous environment. The few trips in the winter to the west of MI suggest that this is a short-term response to varying prey availability rather than a long-term foraging tactic. Six years of observer-based attendance cycle data were used to augment telemetry data. Multi-state mark-recapture models were used to determine the probability of a female being missed when she was present (detection probability). Attendance data were corrected accordingly. Neither El Niño (EN) nor anomalous seasurface temperature (SSTa) influenced any of the attendance cycle parameters, as foraging trip duration is a poor predictor of weak environmental change. Only season and pup sex had a significant impact on female provisioning rates. Foraging trip duration was longer during winter than during summer. Females spent a higher percentage of time on land when they had female pups rather than male pups. Although observational attendance data remain useful it ideally requires concomitant data on pup growth, production and female body condition to elucidate changes in female provisioning rates. Temporally, season had the most influence on female foraging behaviour. Spatially, it appears that a lack of prominent local bathymetrical features overshadows MI's favourable position in the productive Polar Frontal Zone. Arctocephalus tropicalis females from MI work harder at foraging than at any other island population of conspecifics. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Zoology and Entomology / Unrestricted

No description available.