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Diptera in food webs of wetland ecosystems
Pijálková, Helena ; Hadrava, Jiří (advisor) ; Kolář, Vojtěch (referee)
Families of the order Diptera are frequently found in freshwater wetlands, affecting nearly all trophic levels, serving as detritivores, herbivores and predators. Diptera are characterised by an enormous ecological variability of their larval life strategies, which often differ even within individual families. Their adults form an important connection between the aquatic environment of a wetland with its terrestrial surroundings. As a result, adults of various wetland Diptera may serve as pollinators, predators and a prey of other animals including humans. Until now, research of food webs in wetland ecosystems has been focused mainly on a few economically significant groups of Diptera such as mosquitoes, or has been focused on the role of Diptera in transfer of heavy metal from wetlands to other ecosystems. However, overall wetland dipteran diversity still remains understudied. Examining the roles of insects as well as other organisms in food webs is important for example to simulate possible consequences of introduction or extinction of certain species on ecosystems. Further research is therefore necessary to understand how do various dipteran taxa affect other organisms in wetlands as well as their surroundings. Keywords: Diptera, wetlands, ecological webs, detritivory, herbivory, predation
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Synurbanization in wood pigeon (Columba palumbus) and Eurasian magpie (Pica pica)
Tesařík, Jáchym ; Lučan, Radek (advisor) ; Hořák, David (referee)
Both Eurasian magpie and Wood pigeon are typical synanthropic bird species. By studying the available sources, I found that during their synurbanisation, both species have undergone several changes that have facilitated their transition from rural to urban habitats. Due to their adaptability, they have no problems colonizing urban environment and have managed to occupy new and diverse range of nest sites. Thanks to synurbanisation, both Magpie and Wood Pigeon have been able to expand their range and increase their overall abundance. Possibly the biggest threat to urban populations of both species is nest predation, which locally leads to declining population trends and reduced breeding success. Because of predation pressure and the adaptability of both species, I think we can expect not only an increase in abundance and population density in their urban population in the future, but also the occupation of new and more diverse nesting habitats in closer proximity to human settlements.
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The effect of amoeba predation on the evolution of virulence in human pathogenic microorganisms
Drncová, Eliška ; Šuťák, Róbert (advisor) ; Konupková, Anežka (referee)
Amoebae act as one of the main regulators of microbial communities, where, as a result of their predation, selection pressure is exerted for the emergence of defence mechanisms to achieve resistance. This adaptation allows microorganisms to randomly infect the human body and successfully defend against components of innate immunity, especially macrophages, which, like amoebae, are phagocytic cells. The manifestation of virulence in opportunistic pathogens is due to conserved macrophage pathways used for degradation of ingested material, which the microorganism has already encountered in amoebae. Because of this similarity, amoebae can be used to investigate the interaction between a pathogen and its host, which includes research on the virulence mechanisms of many human microbial infections. Among the most extensively studied organisms whose pathogenicity results from long-term interaction with amoebae are the bacterium Legionella pneumophila and the microscopic fungus Cryptococcus neoformans, with very different virulence strategies and manifestations. Understanding the evolutionary context and the advantages that microorganisms gain during interaction with amoebae informs us about the origins of virulence of opportunistic human pathogens.
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Faktory ovlivňující početnost nepůvodního savčího predátora kočky domácí (Felis catus) ve středoevropské kulturní krajině a lidských sídlech.
KALENDOVÁ, Pavlína
The domestic cat is currently one of the most widespread invasive predators, which causes great losses to populations of many species. Due to its strong association with humans, individuals of this species are found on almost every continent and many islands, where it acts as a strong extinction factor. Using point counts, I surveyed the abundance of cats and bird species in the vicinity of České Budějovice and evaluated whether selected environmental factors influence the presence of domestic cats. The selected factors included site type, habitat, weather, temperature, season, and amount of vegetation at the site at the time of the inspection. The weather was only factor that had a statistically significant effect. Specifically, more cats were recorded on partly cloudy and sunny days than on bright or gloomy days. I also investigated whether the presence of the domestic cat at a given location has an effect on the number of recorded bird species or the number of individuals. According to the results, the presence of one or more cats at particular sites did not have a statistically significant effect on the number of bird species or the number of individuals.
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Domestic cats (\kur{Felis catus}) as a phenomenon in the conservation biology - their impacts on biodiversity
NOVOTNÁ, Nikola
Lately, a negative impact of ferocious domestic cats on environmental diversity has been ascertained. Using questionnaires, long term observations of cat prey (prey they brought home) and using database data (NDOP, rescue stations and ringing stations) we were finding out about the composition of cat prey throughout the year in the Czech Republic. Based on the questionnaire results, cats bring home 5x more mammals than birds. Out of the results of a long-term cat prey observation it turns out that cat prey consisted of, out of 93% mammals, 6% birds and out of 1% reptiles and insects. In the first observed season (winter), an average of 1 cat brought a 0.02 prey per day, in the second season (summer) 0.21 prey per day, and in the third season (autumn) 0.38 prey per day. Out of the obtained information it turns out that the cat´s impact on environmental diversity is greatest during the third observed season, and is the lowest during the first observed season. The mammal hunted for most frequently was a vole, while the bird hunted for most frequently was a sparrow. Based on our results, birds were carried home most frequently during the summer season, while mammals were carried home most frequently during both the summer and autumn seasons, which was caused by the fact that mostly all kinds of animals were mating during this time. For cats, it is then relatively easy to catch inexperienced young individuals. Out of all the hunted prey, 2.6% consisted of animals being officially protected in the Czech Republic. Thus, the cat´s impact on protected animals in the Czech Republic was proven.
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Is the growth of brown frog's tadpoles influenced in different stages of its development by the presence of red-eared slide?
VODRÁŽKOVÁ, Magda
In the last few decades, the frequency and importance of invasive species has been increasing mainly due to the disproportionate growth of world trade in animals and plants. Predator-prey interactions drive the evolution of many behavioral and morphological traits in aquatic animals. In aquatic environments, chemical cues reliably enable prey to assess and avoid predation risk. The presence of a predator affects prey populations either by direct predation by reducing its abundance and changing its behavior, or by modifying various parts of its life history. The effect induced by the risk of predation can have a stronger impact on populations than the direct effect of mortality. Non-native red-eared sliders (Trachemys scripta elegans) have the potential to disrupt aquatic ecosystems in Central Europe because of their superior competitive abilities and omnivorous diets. I investigated whether continuous predator-borne cues are tied to changes in the hatching time, developmental stage, and body size at hatching of common frog tadpoles (Rana temporaria). Whether the developmental rates, growth rates and sizes at metamorphosis would alter in the presence of a predator and examined the dynamics of the ontogeny of tadpoles under different time patterns of an alien predator presence. The presence of a predator affected all factors examined. I found that in the absence of the slider, the embryos hatched in 12 days, while hatching was accelerated by two days in slider treatment. At the same time, the embryos hatched smaller and at a lower stage of development with the slider than without it. The presence of turtles shortened the time at metamorphosis of tadpoles from 110?11.7 days to 93?13.0 days (mean ? S.D.). The froglets were significantly smaller (12.8?0.99mm) in the presence of the predator than in the control treatment (15.2?1.27mm). The growth rate trajectories were similar between the predator treatment and the control. Thus, predator-induced tadpole defences were evident in higher developmental rates and smaller sizes at metamorphosis without significant changes in growth. I also found out that the tadpoles had a longer larval period and were smaller in size at metamorphosis and lower in body mass when the predator was present in early development than when the tadpoles developed without a predator. The early presence of a predator conspicuously reduced the growth increments of the tadpoles at early development. After the removal of the predator, growth accelerated above the level measured under the conditions of both the late predator and no predator. However, these growth rates did not exceed the growth rates of equally sized tadpoles in the other treatments and therefore were not sufficient to compensate for the growth slowdown in the first part of development. The presence of a predator in late tadpole development influenced neither the time to metamorphosis nor size/body mass at metamorphosis. Results show rather rarely documented types of amphibian prey responses to caged predators. This study extends the range of predators studied, including the effect on different phases of development of potential amphibian prey.
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Koktejl invazivních druhů ve vnitrozemských vodách - ekologická charakteristika, vzájemné působení a následky
ROJE, Sara
This thesis combines four main chapters: 1) a general summary of the current knowledge of the impact of aquatic invasive species in Europe, ecological characteristics, main representatives, their interaction and the consequences of spread; 2-3) two studies addressing mutual species impacts between invaders co-occurring together in the same habitat; and 4) investigating the differences between the behaviour of native and alien fish species. Chapter 1 looks at the theoretical concept and impacts of aquatic invasive species and in particular, four chosen groups of invaders with a review on specifically chosen high-profile aquatic invasive species in freshwaters, their associated impacts and detailed descriptions of the species used in experiments. Chapter 2 focuses on the predatory impact of killer shrimp on the early developmental stages of marbled and signal crayfish, concluding that killer shrimp are almost unstoppable. They were able to feed on different developmental stages of larger freshwater crustaceans even if they were protected by their mothers. Chapter 3 observes the interactions of two invaders: the round goby and the marbled crayfish. The round goby showed dominant aggressiveness consuming all the juvenile crayfish sizes offered. The study also confirmed that the round goby was able to predate on, attack and take shelters from crayfishes. The only limiting factor in this interaction was the larger size of the crayfish. When interacting, both tested species negatively influenced each other, which can mean mutual consequences for both species. In Chapter 4, the individual behaviour during day and night activity under laboratory conditions in a flow simulator was studied. Both species showed very similar behaviour, with only slight differences towards adaptability and stress-related activity. Despite the similarities, the round goby was confirmed to be an aggressive, bottom-dwelling predator sharing a habitat with a lot of other benthic animals like amphipods, crayfish, and other fish - native or other aliens. In general, all alien species are present a threat to all populations sharing similar characteristics in their habitat, taking their shelters, attacking them, and predating on them with invasive amphipods and crayfish being no exception. One species can limit the other, or the outcompeted species can be displaced forcing it to find an alternative niche and therefore increase the overall pressure on the ecosystem. The presented thesis is submitting some new findings mainly about the interactions between invaders and also represents a baseline for future experimental work focused on more complex setups that will enable us to increase our understanding of invasive species.
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Interactions between plants, herbivorous insect and predators: mechanisms and ecological importance
MRÁZOVÁ, Anna
The thesis describes the interactions between the three trophic levels from different perspectives. It focuses on the role of plants, herbivorous insect, and invertebrate predators and birds in trophic interactions. More specifically, it describes indirectly induced plant defence and communication with higher taxa and changes in predation pressure and insect communities in response to defensive chemical compounds released from herbivory-damaged plants.
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