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Long-distance migrations of hover flies (Diptera: Syrphidae)
Hlaváček, Antonín ; Hadrava, Jiří (advisor) ; Černý, Martin (referee)
Long-distance migration of insects is well-known phenomenon, studied especially in butterflies and locusts. Until now, the migration of hover flies (Diptera: Syrphidae) was considered a rather marginal issue and not much attention has been given to it. However, billions of hoverflies take part in the spring and autumn migration every year, transferring hundreds of tonnes of biomass and nutrients. The aim of this thesis is to review an existing knowledge on the migration of hoverflies in context of their ecology and evolution. In the first part, I discuss the biogeography and diversity of migratory hover flies, methods for studying migration and the application of such methods in hover flies migration. In the following chapters, I focus on the migration of particular species in context of their ecology and evolution, especially on population dynamics, phenology, orientation, and dimorphism in the migratory generation.
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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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Dynamics of pollination networks in time and space
Matějková, Zuzana ; Hadrava, Jiří (advisor) ; Tropek, Robert (referee)
This bachelor's thesis focuses on changes in pollination networks on different spatio-temporal scales. It covers in detail the essence and magnitude of these changes in communities of pollinators and plants. The thesis outlines the consequences of these changes for these communities and the way it affects the methodological aspects of studying plant-pollinator networks. I present the existing dynamics of Pollination networks on broad geografical scales as well as changes in local communities. I also describe the temporal changes of communities of plants and pollinators, consisting of diurnal and seasonal dynamics, not exluding the changes on even broader temporal scales. It has been shown that plant-pollinator networks are highly dynamic in space and time. These dynamics consist of species and interaction turnover, as well as of changes in the overall diversity of communities of plants and pollinators. Biodiversity dependent characteristics of pollination networks are affected by the described spatio-temporal dynamics, while characteristics that are biodiversity independent stay relativly stable on broader temporal scales.
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Crypsis at dragonflies
Záhorová, Kristýna ; Černý, Martin (advisor) ; Hadrava, Jiří (referee)
Crypsis is one of the defens mechanisms used by animals to hide from predators. It is a form of coloring that allows prey to blend in with their surroundings or makes difficult for predators to see them due to disruptive coloration. Dragonflies utilize crypsis across different families and sometimes even within individual species in various types of environments, ranging from savannas to tropical rainforests. Crypsis also serves as a defense mechanism not only against predators, but also against members of their own species, where females avoid sexual harassment from males and young males avoid fighting with adult males. This is related to changes in coloration during ontogenetic development, as well as the sometimes pronounced sexual dimorphism that is relatively common in dragonflies. Additionally, larvae of dragonflies are often cryptically colored. This study focuses on cryptically colored dragonflies from around the world and in various types of environments. Rather unexpectedly there are not many studies focing on this phenomena at otherwise throroughly studied group of insects. Key words: dragonflies, crypsis, cryptic coloration, sexual dimorphism, dragonflies larvae
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Ecological and Evolutionary Processes Driving the Structure of Plant-Pollinator Networks
Hadrava, Jiří
Associations between flowers and pollinators are responsible for reproduction of majority of plant species as well as food supply for substantial part of animal diversity on the Earth. Until recently, the studies on plant-pollinator relationship were focused predominantly on pollination of particular plant species, with only little or no accent on community perspective. In recent decades, however, pollination ecology shifted its focus rather to community context by introducing so called pollination networks. This approach allows us to view the ubiquity and complexity of the interactions between plants and their pollinators and it opened up many new opportunities to study the pollination from animal perspective or to access spatio-temporal variability in the interactions. However, we still have only limited insight into the processes driving the structure and dynamics of such networks. The assembly of plants, pollinators and their interactions are driven by various ecological as well as evolutionary processes. From the ecological point of view, species co-occurrence in time and space may affect the interactions, or species flexibility for various community contexts providing different food sources may play role. In the evolutionary perspective, species may have various co-adaptations due to their...
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Ecological and Evolutionary Processes Driving the Structure of Plant-Pollinator Networks
Hadrava, Jiří ; Klečka, Jan (advisor) ; Gilbert, Francis Sylvest (referee) ; Vujić, Ante (referee)
Associations between flowers and pollinators are responsible for reproduction of majority of plant species as well as food supply for substantial part of animal diversity on the Earth. Until recently, the studies on plant-pollinator relationship were focused predominantly on pollination of particular plant species, with only little or no accent on community perspective. In recent decades, however, pollination ecology shifted its focus rather to community context by introducing so called pollination networks. This approach allows us to view the ubiquity and complexity of the interactions between plants and their pollinators and it opened up many new opportunities to study the pollination from animal perspective or to access spatio-temporal variability in the interactions. However, we still have only limited insight into the processes driving the structure and dynamics of such networks. The assembly of plants, pollinators and their interactions are driven by various ecological as well as evolutionary processes. From the ecological point of view, species co-occurrence in time and space may affect the interactions, or species flexibility for various community contexts providing different food sources may play role. In the evolutionary perspective, species may have various co-adaptations due to their...
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Influence of plant pollinator spectra generalization on plant reproductive success
Hanusová, Natálie ; Štenc, Jakub (advisor) ; Hadrava, Jiří (referee)
Plants are pollinated by variously wide pollinator spectra. Plants pollinated by a wide spectrum of pollinators are called generalized plants. There are many factors leading to the generalized strategy of plants including their morphology, environment context, local pollinator community, and competition between plants for effective pollinators. However, generalization is connected to potential risk because not all pollinators are equally efficient and effective. The Generalization of plants is a very flexible way how to deal with non-predictable conditions and achieve successful sexual reproduction. Further investigation is needed to understand how the generalization of plant-pollinator spectra shapes plants sexual reproduction. Keywords: pollinator spectra generalization, pollination, plants reproduction, plants reproductive success
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Methods in research of insects mobility
Jor, Tomáš ; Hadrava, Jiří (advisor) ; Lučan, Radek (referee)
Mobility is one of the basics characteristics of the insects populations. This bachelor thesis presents a compendium of methods used in research of insects mobility. In the first part are described methods of marking individuals utilized for Mark-Recapture studies aiming to study insects movements. First are presented the indirect methods of individuals tracking, further the methods of direct tracking of insects using a radio-telemetry are described. In the second part the thesis focused on modeling of insects mobility using dispersion functions with connection to metapopulation dynamics and a dispersion itself. Difusion model based methods and simpler estimates of movemensts are also presented in this part. Key words: Insects, Mobility, Mark-Recapture, Modeling
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Mimicry in hoverflies
Daňková, Klára ; Hadrava, Jiří (advisor) ; Raška, Jan (referee)
Batesian mimicry, the imitation of harmful species manifested by harmless ones, could bring a lower risk of predation to the mimetic species. Therefore, it occurs in many different taxa. Hoverflies (Diptera: Syrphidae) could stand for one of the most various mimics. This worldwide-distributed family is known for taking shape of many Aculeata species using plenty of different adaptation connected with colouration, morphology and even behaviour. The aim of this work is to review the diversity of mimicry in Syrphidae, highlight the main selection pressures and to put forward a potential field of future research. Hoverflies are being studied for the last two hundred years. However, just several study approaches are dominating the field. In order to open a new chapter of their research, I bring a wider synthesis of knowledge related to the ecological and evolutionary context of this phenomenon.
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Ecology of pollination networks
Hadrava, Jiří ; Janšta, Petr (advisor) ; Novotný, Vojtěch (referee)
In communities, plants and pollinators are organized into complex network of relations. Description of structure in this network can contribute to understanding of community dynamics and persistence of biodiversity. Better understanding of patterns in assemblages of plants and pollinators may also help in their protection. The aim of this work is to review recent methodological principles in the pollination network analyses and to show potential problems in concept of ecological networks. Graph theory is breefly summarized and applied to the description of pollination networks. As an example, results on comparison of communities from different geographical sites are given.
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