Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Includes bibliographical references.

The long history of co-existence of bacteria and their protozoan predators in aquatic environments has led to evolution of protozoa resistant bacteria (PRB). Many of these bacteria are also pathogenic to humans. However, the ecological drivers determining the occurrence of different types of PRB in aquatic environments, and the eco-evolutionary link between bacterial adaptation and the resulting implications for mammalian hosts are poorly known. This thesis examines the impact of nutrients and predation on PRB, as well as the ecological and evolutionary connection between their life in aquatic environments and mammalian hosts. In the first study seven bacterial isolates from the Baltic Sea were investigated for their plasticity of adaptation to predation. The response to predation showed large variation where some bacteria rapidly developed a degree of grazing resistance when exposed to predators. The rapid adaptation observed may result in bacterial communities being resilient or resistant to predation, and thus rapid adaptation may be a structuring force in the food web. With the aim to elucidate the link between occurrence of PRB and environmental conditions, a field study and a laboratory experiment were performed. In both studies three PRB genera were found: Mycobacterium, Pseudomonas and Rickettsia. PRB were found both in oligotrophic and eutrophic waters, indicating that waters of all nutrient states can harbor pathogenic bacteria. However, the ecological strategy of the PRB varied depending on environmental nutrient level and disturbance. Using an advanced bioinformatic analysis, it was shown that ecotypes within the same PRB genus can be linked to specific environmental conditions or the presence of specific protozoa, cyanobacteria or phytoplankton taxa. These environmental conditions or specific plankton taxa could potentially act as indicators for occurrence of PRB. Finally, using four mutants (with specific protein deletions) of the pathogenic and predation resistant Francisella tularensis ssp. holarctica, I found evidence of an eco-evolutionary connection between the bacterium´s life in aquatic and mammalian hosts (aquatic amoeba Acanthamoeba castellanii and a murine macrophage).  To a large extent F. t. holarctica use similar mechanisms to persist predation by protozoa and to resist degradation by mammal macrophages. To summarize I found a link between predation resistant bacteria in aquatic environments and bacteria that are pathogenic to mammals. Further, I showed that different environmental conditions rapidly selects for PRB with either intracellular or extracellular lifestyles. This thesis provides insights regarding environmental conditions and biomarkers that can be used for assessment of aquatic environments at risk for spreading pathogenic bacteria. / <p>Medfinansiärer var även: Swedish Ministry of Defence (A4040, A4042, A404215, A404217), Swedish Minestry of Foreign Affairs (A4952), Swedish Civil Contingencies Agency (B4055)</p>

Orientador: Odair Aparecido Fernandes / Resumo: A mosca-branca Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biótipo B é uma das principais pragas agrícolas no Brasil e no mundo. O objetivo do presente estudo foi avaliar o potencial de predação de Amblyseius tamatavensis Blommers (Acari: Phytoseiidae) em cultivo protegido de tomate, bem como a dinâmica dos fatores de mortalidade de mosca-branca. Para tanto, foram conduzidos experimentos em laboratório e estufa. Inicialmente foi avaliada a preferência de predação por ovos e ninfas de B. tabaci. Posteriormente foi determinada a resposta funcional e numérica de A. tamatavensis sobre imaturos de B. tabaci. Também foi avaliada a eficiência de A. tamatavensis no controle de B. tabaci sobre plantas de tomate. Por último, a dinâmica dos fatores naturais de mortalidade de mosca-branca foi comparada entre cultivos de tomate infestados com B. tabaci na presença ou ausência de A. tamatavensis. Os resultados mostram que A. tamatavensis tem preferência por estágios iniciais de B. tabaci (ovos, ninfas do primeiro e segundo instar). A resposta funcional é do tipo II e o ácaro alimentado com ovos de B. tabaci pode ovipositar 1,4 ovos/dia. A liberação de 26 ou 78 ácaros predador/m2 logo após a infestação de mosca-branca apresentam o mesmo nível de controle. Com isso estão estabelecidas as bases para um programa de controle biológico da mosca-branca. / Abstract: The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B is one of the main agricultural pests in Brazil and worldwide. The objective of this study was to evaluate the predation potential of Amblyseius tamatavensis Blommers (Acari: Phytoseiidae) in protected tomato cultivation, as well as the dynamics of whitefly mortality factors. Experiments were carried out in laboratory and greenhouse. Initially, the predation preference for eggs and nymphs of B. tabaci was evaluated. Subsequently, the functional and numerical response of A. tamatavensis on immature B. tabaci was determined. The efficiency of A. tamatavensis to control B. tabaci on tomato plants was also evaluated. Finally, the dynamics of natural whitefly mortality factors were compared between B. tabaci infested tomato crops in the presence and absence of the predator A. tamatavensis. The results showed that A. tamatavensis has a preference for early stages of B. tabaci (eggs, first and second instar nymphs). The functional response is type II and the mite feeding upon B. tabaci eggs can oviposit 1.4 eggs/day. The release of 26 or 78 predatory mites/m2 soon after whitefly infestation has the same level of control. This establishes the foundation for a whitefly biological control program. / Doutor

It is a widely accepted assumption that fish predation controls structure and functioning of aquatic food webs. In the past, however, a large part of effort was concentrated on lakes and reservoirs. Thus, the knowledge about stream ecosystems is much more rudimentary than that for lakes in this respect. The aim of this thesis, therefore, was to describe and assess the effects of fish predation in natural stream ecosystems. For that purpose a reach scale field experiment was set up using an experimental stretch with benthivorous fish and a fishless reference stretch. A wide range of effects of the fish predators on their stream invertebrates prey was studied. To discriminate between lethal and sublethal predation effects, measuring the physiological status of the organisms seemed promising. However, before it was possible to decide whether or not environmental stress, such as predation, might affect the physiological status, the internal control as well as the seasonal and species-specific variability of the energy amount stored had to be assessed. Thus, the concentration and seasonal dynamics of the major energy storage components triglycerides and glycogen were measured in two species of mayflies (Rhithrogena semicolorata and Ephemera danica) with contrasting life cycle strategies. E. danica is a burrowing, semivoltine collector-gatherer, R. semicolorata is univoltine and scrapes periphyton from stones. Although triglycerides are the major energy reserve in both species throughout the whole larval development (&amp;gt; 84 % of total energy storage) their seasonal dynamic differed considerably. In R. semicolorata the triglyceride concentration declined during the last weeks prior to emergence in both sexes. The same pattern was found in female larvae of E. danica, but not in male E. danica. It is suggested that females use triglycerides in the last larval stages for egg maturation, which is completed in the last larval instar. In male E. danica the triglyceride concentrations remained high until emergence, presumably due to their high energy demands as adults for their swarming flights and mating. The difference in seasonal variation of triglycerides between E. danica and R. semicolorata shows the influence of environmental factors on the dynamics of storage components. E. danica lived in a very stable environment (within the substratum). Therefore the dynamic of energy storage components was optimised with respect to maximal reproduction. R. semicolorata on the other hand, suffered from hostile environmental factors such as predation or food limitation due to low periphyton biomass after leaf sprout and following light limitation in spring. Consequently, the concentration of storage components decreased during spring. One conclusion from this study was that the measurement of storage components might reveal sublethal predation effects. However, season and sex of the organisms are important factors as well and have to be considered in the sampling design. To analyse sublethal predation effects behavioural changes due to the presence of benthivorous fish were measured. Drift as a low-energy cost means of migration may enable stream invertebrates to leave risky habitats or may even be a direct escape reaction after a predator encounter. While the control of drift activity by predators has received considerable interest from many researchers, it remains still unclear whether predators reduce or increase drift activity. Drift activity of stream invertebrates was influenced significantly by the presence or absence the two benthivorous fish species gudgeon (Gobio gobio) and stone loach (Barbatula barbatula). Contrary to previous studies gudgeon and stone loach reduced invertebrate drift density and drift activity of Baetis rhodani rather than inducing higher night-time drift. Further, species composition of the invertebrate drift differed significantly between the two stretches. A further conclusion from this study is therefore that drift is not generally a mechanism of active escape from benthos-feeding fish, as previously assumed. In addition, the reduced drift activity in the fish stretch might result in a compensation of the consumptive losses due to fish predation. Thus, in this study design the effects of fish predation on invertebrate community might be underestimated. To detect predation effects on the food web structure the reactions of the grazing mayfly Rhithrogena semicolorata and the shredding amphipod Gammarus pulex to strong predation by benthivorous fish were compared. It has been hypothesised that shredders are generally less vulnerable to fish predation and therefore less likely to be predation-controlled than grazers, because the latter are visible to the predators during their feeding on stone surfaces, while shredders may hide between leaves during foraging. Biomass of G. pulex was significantly reduced in the fish stretch while that of R. semicolorata was not. Since approximately 91 % of the annual production of G. pulex but only 12 % of R. semicolorata production was consumed by benthivorous gudgeon, the observed difference of G. pulex biomass between the fish and reference reach is likely due to a lethal predation effect. However, no sublethal predation effects such as reduced concentration of storage components (triglycerides, glycogen) or reduced reproductive success were observed for both species. Hence, in contrast to the initial hypothesis, in the studied stream the shredder was top-down-controlled, while the grazer was not. It is concluded that top-down control depends on the ecological characteristics of a specific predator-prey pair rather than on trophic guild of the prey. To assess the predation effects on the life history of merolimnic insects and its consequences on fecundity the larval development and emergence of R. semicolorata was studied. It was possible to show lethal and sublethal effects of predation by benthivorous fish (Gobio gobio, Barbatula barbatula). Predation consequently resulted in changes of larval development and population fitness. The presence of two benthivorous fish species (gudgeon and stone loach) led to slower larval development and a delayed emergence. However, no differences in the adult size and fecundity between the fish reach and the reference were observed. Nevertheless, the longer time spent in the larval phase resulted in a higher mortality and therefore in a lower mean population fitness. The presence of gudgeon alone, however, did not seem to influence larval development, growth or time of emergence and consequently fecundity. Further, strong lethal impact of gudgeon could not be detected. Thus, the population fitness measured as the product of adult density and egg number was not reduced by gudgeon alone. It is assumed that the stronger lethal impact in the combined fish experiment is caused mainly by stone loach because the proportion of mayfly consumption by stone loach to mayfly production shortly before emergence was higher than the proportion related to gudgeon. Thus another conclusion is that 1) the impact of predation seems to differ for the fish species and 2) lethal effects have a stronger impact on the population survival than life history changes. Combining the results mentioned above leads to the assumption that predation by benthivorous fish has the potential to shape invertebrate communities and food webs in streams. It was possible to show reductions of benthic densities and mean population fitness. The strength of trophic interactions seemed to be specific for the single predator-prey pairs here. Finally, it can be stated that contrary to previous assumptions consumption of the fish predators seemed to be more important for the prey populations than sublethal predation effects.

Lethal interactions between carnivorans (interspecific killing) may influence their population dynamics, behavior, and other important aspects of their ecology. In this study, I expand upon previous research on the broad-scale patterns of interspecific killing in Carnivora (Palomares & Caro 1999, Donadio & Buskirk 2006) with a greatly expanded dataset (inclusion of scat and stomach data and more intensive sampling of the literature), and suggest avenues for future research. While like previous studies, I found a positive effect of relative body size between killer species and killed species on the likelihood of forming a killing interaction, I failed to find evidence that this effect had a body size ratio threshold above which interactions become less common, suggesting a greater role of non-competitive killing than previously believed. I also found evidence for a positive influence of range overlap and dietary overlap on species interactions, but found mixed effects of phylogeny. This study suggests that our previous understanding of the broad-scale dynamics interspecific killing in Carnivora was, due to limited sampling, incomplete in scope. Incidental killing, whereby killing interactions occur as a byproduct of opportunistic lethal encounters caused by the hyperpredatory behavior of carnivorans, has a number of interesting implications for our understanding of interspecies aggression, including research on intraguild predation and its effects.

Betesskador kostar Sveriges skogsbruk stora summor varje år orsakade av älgbland annat. Vargens återkomst och mänsklig jakt har stor påverkan på älgpopulationen och trots en minskad älgstam så visade studier på att betesskadorna var oförändrade och till och med ökade. Studiens syfte var att utreda om man med hjälp av befintlig statistik från älgbetesinventeringar, avskjutningsstatistik för älg samt varginventering bekräfta att betesskadorna borde minskat i områden med vargrevir. Någon statistisk signifikans kunde inte bekräfta att betesskadorna minskade inom vargrevir och en trolig förklaring var stora mellanårsvariationer i älgbetesinventeringen samt för få variabler.Största anledningen till betesskador verkade mera bero på skogsbruket och skogens sammansättning och inte på hur mycket älg det fanns, trots stor predation och jakt så minskade inte betesskadorna.

Changes in abundance of interactive species can have cascading, community-wide effects (Soule et al. 2003). Raccoons (Procyon lotor) prey on a competitor for marine turtle eggs, the Atlantic ghost crab (Ocypode quadrata). Conservation of marine turtles often includes managing raccoons-the most obvious egg predator-which may have broader ecological effects, and unknown effects on egg predation. Neither the relationship between raccoons and ghost crab density nor the effects of ghost crab density on egg predation are well understood. I studied raccoon-ghost crab interactions and the effects of environmental variation on their activity during the 2007 marine turtle nesting season on Canaveral National Seashore, FL. My goal was to model predator activity and identify efficient management strategies to reduce egg predation. Raccoon activity increased with increasing habitat diversity and edge of the dominant cover type, coastal strand. Raccoon activity increased locally and became less variable near segments of beach accessed for human recreation, but activity was greater on undeveloped beach, where habitat diversity and edge were greater. Ghost crab density and size were primarily affected by sand characteristics and recreation but decreased with increasing raccoon activity in June, which may have contributed to sustained declines in ghost crab density. Hatching success of marine turtles decreased with increasing ghost crab egg predation, suggesting ghost crabs are an important cause of egg mortality and not merely scavengers on unhatched eggs. Egg predation by ghost crabs was unrelated to ghost crab density or size, likely a result of monitoring limitations, but raccoon activity increased with increasing egg predation by ghost crabs, supporting previous research and experimental evidence suggesting ghost crabs can facilitate secondary nest predation by raccoons. This indirect interaction has strong implications for marine turtle conservation, because its strength may increase with increasing ghost crab density, potentially negating the effects of raccoon removal.

No description available.

Members of a guild of cursorial spiders (Pardosa spp. and Alopecosa spp.) spatially segregated among five discrete habitats, from a streamside cobble habitat grading laterally along a successional gradient to the leaf litter zone of a transition or climax riparian forest. Seasonal activity peaked in midsummer for all guild members. Spiders were active diurnally earlier in the streamside habitats, and levels of activity were positively correlated with light intensity. Guild members Pardosa tristis and Pardosa uncata were most different in habitat selection and periods of diurnal activity. Males and females of all guild species differed in their distribution among habitats and over months of collection. Measures of guild species diversity and evenness were variable between habitats, and were largely influenced by the relatively high abundance of one or two guild species, particularly in the streamside habitats.

The Baltic Sea is highly affected by eutrophication, but more knowledge is needed regarding how this influences many of the organisms that live there. One understudied species is the moss animal Einhornia crustulenta. In this study, steps are taken towards better understanding the ecology of E. crustulenta and how it might be influenced by eutrophication. This was done by two experiments. In the first experiment, it was tested whether E. crustulenta can feed on some phytoplankton species connected to eutrophication in the Baltic Sea (including e.g. the filamentous cyanobacteria Nodularia spumigena and Aphanizomenon flos-aquae and the flagellate Prymnesium parvum). In the other experiment, it was tested whether the snail Theodoxus fluviatilis and the isopod Idothea baltica are potential predators on E. crustulenta in the Baltic Sea. The results show that E. crustulenta are able to feed on e.g. N. spumigena and P. parvum and thus might be benefitted by eutrophication. Furthermore, the results show that neither T. fluviatilis nor I. baltica seem to feed on E. crustulenta. The results from both studies imply that E. crustulenta might benefit from eutrophication in the Baltic Sea and expand without control from predators. Here, some steps have been taken towards better understanding the ecology of E. crustulenta, but further research is needed. Future studies could include more potential predators and also study earlier life stages of E. crustulenta.