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Seasonality and weather conditions jointly drive flight activity patterns of aquatic and terrestrial chironomids
VEBROVÁ, Lucie
Dispersal by flight is crucial for long-term survival of organisms inhabiting dynamic environments, especially small standing waters. Surprisingly, flight activity of the most abundant macroinvertebrate group in standing freshwater habitats, the Chironomidae, has rarely been studied, leaving a gap in our understanding of the environmental drivers of their dispersal activity. The goal of this study was to investigate flight activity of adult chironomids on diel and seasonal timescales in sandpit pools in the Czech Republic. We show that aquatic and terrestrial chironomids use partly alternating time windows for their flight and partly differ in their responses to weather conditions. We also compare our results to previous studies that analysed the impact of weather conditions on flight activity of aquatic insects.
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Efficiency of subaquatic light traps depending on a size of entrance hole and time of exposure
LIEBL, Lukáš
This bachelor thesis examines the capture of aquatic insects, using the subaquatic light trap method. The aim of this thesis is to determine in depth the extent of effectiveness of aquatic insects capture depending on two major factors. The size of the trap's entrance holes and the daylight exposure time (after the night capture). The result of this theses is the assessment of what size of the entrance holes is optimal for the capture of aquatic insects and how this entrance size affects the escape rate of individuals out of the trap. Moreover, the study examines whether the escape rate is affected by the exposure time of the light trap in the water. The experiments were conducted in the school educational garden of the Faculty of Education of the University of South Bohemia in České Budějovice during autumn 2015 and summer 2016, using aquatic light traps with different entrance hole sizes. As model organisms representatives were used species of water insect families Corixidae, Chaoboridae and Notonectidae.
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Microhabitat preferences for overwintering water bugs
ČIHÁK, Petr
This diploma thesis deals with overwintering of water bugs. The goal of the thesis is to experimentally find out what microhabitats do these water bugs prefer for overwintering. The experiment took place in the greenhouse in the educational garden of PF JU in České Budějovice (48° 58'32.182 "N, 14° 26'54.218" E) from the beginning of November 2017 to the beginning of March 2018. Terrestrial and water microhabitats were created in the greenhouse. They served as a place for potential overwintering of the water bugs. Defined numbers of individuals of given species were put into the center of the greenhouse in boxes with small amount of water. The source of the water bugs were surrounding ponds and a pool in the educational garden. At the end of the experiment, all microhabitats and their surroundings were closely looked through. The found individuals (both alive and dead) were counted and put into sample containers filled with concentrated alcohol. The results are following. Notonectidae prefer mainly water microhabitats, mainly when there are rotting leaves. Corixidae do not prefer any of these microhabitats and presumably they escaped through the little holes in the greenhouse. Nepidae stayed in the original box throughout the experiment. The Ranatra linearis died, whereas Nepa cinerea survived until frosts that caused complete freezing for several following days.
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A species selectivity of subaquatic light traps
BOHDALOVÁ, Markéta
The bachelor thesis deals with capturing water insects using the technology of light traps. The main goal of the research is to determine selectivity of subaquatic light traps capture in detail, using this kind of traps, and also find out some species specific diferences in success of the capture. The base of the research are mesocosmic experiments with accurately defined community of nectonic insects. Corixa punctata, Sigara lateralis, Notonecta glauca and Chaoborus sp. serve as the model organisms in the research.
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An influence of water turbidity on the effectivity of water insects capture rate by subaquatic light traps
ČIHÁK, Petr
The goal of this bachelor thesis is to determine the influence of water turbidity on the effectivity of water insects capture rate by subaquatic light traps. The experiments were carried out at the educational garden of Faculty of Education of the University of South Bohemia (48° 58'32.182 "N, 14° 26'54.218" E) during two years. Four tanks were placed on the garden, each holding 400 l of water. A different amount of clay was dispersed in the tanks and a defined amount of specimens of the stated species were added. The water insects were firstly captured in the nearby ponds and a pool at the educational garden. Then, light traps with different entrance size according to the size of the selected species were used for the capture. The light traps were thrown into the tanks in early evening hours and collected in the early morning. In the morning, all the specimens both in and out of the traps were fixed in concentrated ethanol. The samples were then counted and the species were determined using laboratory equipment. The species of water insects were then statistically evaluated. The experiments resulted in findings that the subaquatic light traps are valuable technique for aquatic insects sampling. The traps were highly effective in the capture of aquatic bugs (water boatmen and backswimmers) and low effective for dipterans (Chaoborus) in both clear and turbid waters. The turbidity does not affect capture rate of selected species of aquatic insects, at least in small water bodies.
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Závislost predace a rychlosti metabolismu na teplotě z pohledu kořisti i predátora
MODRÁ, Denisa
Climate changes affect species interactions which can have cascading effect up to the ecosystem level. This work investigates the effects of temperature and predator size on predator prey interactions by measuring the feeding rates of predators and metabolic rates of both predator and prey, using dragonfly larvae Aeshna cyanea and toad tadpoles Bufo bufo as a model system. Possible consequences of the findings for the impacts of climate change and predation on amphibian populations are discussed.
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Disperzní a letová aktivita pakomárů stojatých vod (Diptera: Chironomidae)
VEBROVÁ, Lucie
I first review the significance of dispersal for individuals and populations including the role of the most significant environmental drivers on separate phases of dispersal. Emphasis is put on aquatic insects inhabiting small standing waters. The following manuscript summarizes a quantitative study of diel and seasonal flight patterns of adult Chironomidae in the Cep II sandpit in southern Bohemia. It provides one of the first comprehensive treatments of the effect of weather conditions and seasonality on the flight activity of adult Chironomidae, phenology of most common species and differences between terrestrial and aquatic species.
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The role of species traits in predator-prey interactions and food web structure
KLEČKA, Jan
This thesis deals with the role of species traits in predator-prey interactions and food web structure. I conducted laboratory experiments with predatory aquatic insects and their prey to reveal the traits determining who eats whom in small standing waters. I also focused on the possibility of incorporating the observed dependence of predator-prey interactions on body mass into existing food web models. Further, I developed a simple simulation model to explore the consequences of body mass dependent feeding and dispersal for food web assembly. Last, I show that four common methods for sampling aquatic insects differ in their selectivity, especially on the basis of body mass of sampled insects. In conclusion, I combined laboratory experiments, field work and mathematical models to evaluate the importance of body mass and other species traits, such as foraging behaviour and microhabitat selectivity, in predator-prey interactions and explored selected food web level consequences.
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