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Evaluation of porosity in Al-alloy die-castings
Straka, Jakub ; Nová, Iva (referee) ; Čech, Jaroslav (advisor)
The purpose of this diploma thesis is an evaluation of die-castings porosity, eventually the evaluation of seats with local squeeze in connection with their mechanical and structural properties. The swatches of alloy AISi9Cu3 were taken from the engine block made by Škoda Auto Company, Mladá Boleslav. To the evaluation and the comparison of the results there were used value of porosity with own measure and other student´s thesis of Brno University of technology. Sets of mechanical and structural properties were selected, evaluated and tested by statistical programs.
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Evolution of sociality and parental care in bees of the genus Ceratina
Mikát, Michael ; Straka, Jakub (advisor) ; Schwarz, Michael (referee) ; Bogusch, Petr (referee)
Small carpenter bees (genus Ceratina) are an excellent model taxon for the study of evolution of parental care and origin of eusociality. Prolonged offspring care is typical for this bee genus. Females usually guard their offspring until adulthood and later feed their adult offspring pollen and nectar. Moreover, most of studied species are facultatively eusocial, a trait probably inherited from the common ancestor of the genus. Although Ceratina bees have generally very interesting behavior, detailed studies were performed in only a few species, usually from North America, Japan and Australia. Only anecdotal observations of natural history existed for a few European species, and detailed research has not been performed before my thesis. The goal of my thesis is to explore the natural history of European species of Ceratina and to identify possible costs and benefits of this species' behavioral traits. I focused on following these behavioral traits: social nesting, guarding of offspring until adulthood, and feeding of mature offspring. Through my master project, I discovered biparental care in species C. nigrolabiata, therefore the most important goal of my Ph.D. project is the evaluation of costs and benefits of this behavior. Guarding of offspring by mother significantly influences their survival,...
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The Effect of Presence and Abundance of Parasites (Nomada, Stylops) on the Host Species Population (Hymenoptera: Andrena) at the Level of Entire Communities
Bureš, Vít ; Straka, Jakub (advisor) ; Libra, Martin (referee)
Bees (Anthophila) play a crucial role as pollinators, vital for maintaining biodiversity in ecosystems. However, the decline in pollinator populations in recent years raises concerns about ecosystem stability. This study investigates the impact of parasitism on host bee populations of the genus Andrena as a potential factor influencing the decline of insects. Additionally, it examines populations of parasites of the genera Stylops and Nomada as indicators of host population status. Bees of the genus Andrena are abundant in the western Palearctic and are commonly parasited by Stylops and Nomada. Leveraging a large dataset from Europe, this study uses abundance data to explore the influence of abiotic and biotic factors on the parasitization rates of host Andrena bees. Specifically, the effects of abiotic factors such as altitude, habitat type, annual rainfall, and average temperature on the parasitization rates by both parasite types has not been confirmed. The results indicate that within small geographical units (sites), larger populations of host Andrena bees are more heavily parasitized by Stylops compared to smaller populations, while this trend does not hold true for Nomada. Interestingly, this study reveals that Stylops and Nomada coexist within the same host populations without competing for...
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Social nest structure of sweat bee Lasioglossum marginatum (Anthophila: Halictidae)
Vinická, Eliška ; Straka, Jakub (advisor) ; Bogusch, Petr (referee)
Family Halictidae is one of the most socially diverse taxa of bees, and especially one of the genera that belongs in this family. It is the genus Lasioglossum, which includes different types of sociality from solitary behavior to eusociality. Among the species of this genus, one stands out and that is the species Lasioglossum marginatum. Its social behaviour was described in the years 1959-1972 by Plateux-Quén in France. Its sociality is eusocial and is completely unique. In its nests there are dozens to hundrets of individuals, all of which are produced by a single queen. The life cycle of this species is not one-year, as in most species, but is spread over 5(6) years and the queen survives the entire time. It is a univoltine species and therefore produces only one generation of offspring per year. This is not unusual, except that eusocial species in this family are always at least bivoltine with a one-year social cycle. In each year of the five-year cycle, the queen produces only workers. Only in the last year of the cycle are future foudresses and males produced. The purpose of this work is to confirm or disprove Plateux-Quénu's statements. Field experiments were performed from 2020 to 2023 in the Kletnice nature reserve in South Moravia. A total of 354 nests were excavated, and their nest...
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Parasitic strategies based on behavioral manipulation of the arthropod host
Janovská, Kateřina ; Straka, Jakub (advisor) ; Votýpka, Jan (referee)
It is well known that parasites can alter the host's behaviour for their benefit or the benefit of their offspring. Arthropods often fall victim to these parasites. Although the parasites of Arthropods come from many different groups (e.g., helminths, insects, fungi, viruses, etc.), we can find some similarities in their strategies. The specific methods and processes of behavioural manipulation are unique to each parasite and depend on whether the arthropod is the parasite's final host or an intermediate host/vector. However, they often lead to the same goal, e.g., to be eaten by another host, to allow the parasite to reproduce or to protect the parasite's offspring. Whether these changes in the host's behaviour are a part of the parasite's life strategy or only a manifestation of an adaptive response of the host remains a question. This thesis discuss specific cases of behavioural manipulation in parasitized arthropods and the common motives parasites use in manipulation. Keywords: behaviour manipulation, Arthropods parasite, parasitoid, host's behaviour, host- parasite interaction, adaptive response
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Evolution of Host Specialisation, Phylogeography and Taxonomic Revision of Xenidae (Strepsitera)
Benda, Daniel ; Straka, Jakub (advisor) ; Malenovský, Igor (referee) ; Cook, Jerry L. (referee)
Twisted-winged parasites (Strepsiptera: Xenidae) are an excellent group for studying the specialisation of parasites on hosts. Their parasitic lifestyle led to the evolution of numerous morphological, behavioural, physiological, and reproductive adaptations. Moreover, many complex adaptive traits of Strepsiptera have no parallel in other organisms. In contrast, little attention has been paid to the study of strepsipteran molecular phylogeny, phylogeography, species delimitation, and their implications for taxonomic classification. Using the methods of molecular phylogeny, we created the first dated phylogenetic study of the family Xenidae. By investigating historical biogeography and ancestral host groups, we indicate that multiple lineages were exchanged between the New World and the Old World + Australia until Antarctica became completely frozen over. During the late Paleogene and Neogene periods, several lineages spread from the Afrotropics to other Old World regions and Australia. The original hosts of Xenidae were most likely social wasps, and the subsequent host switch from social to solitary wasps was secondary and probably occurred only once. The parallel host switch from solitary wasps to digger wasps (Sphecidae) occurred independently in the New and Old World. The biogeography and...
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Factors affecting pollen transfer effectiveness
Švanda, Petr ; Štenc, Jakub (advisor) ; Straka, Jakub (referee)
Pollen transfer efficiency, i.e., the proportion of pollen that is successfully transferred to a plant of the same species, significantly affects plant reproductive biology and creates a potentially strong selection pressure for the development of specialized strategies to increase pollen transfer efficiency. Precisely because of its importance within pollination biology, the efficiency of pollen transfer was a frequent subject of studies, in which, however, its interpretation differed depending on the method used, making it difficult to compare individual studies. Moreover, the work to date does not offer a satisfactory methodological framework for comparing the effectiveness of pollen transfer across the studied systems. The effectiveness of pollinators is primarily affected by the amount of pollen removed, the amount and quality of pollen deposited and frequency of pollinator visits. These factors are affected by additional influences, for example the behavior of the pollinator, the number of open flowers within the inflorescence or the environment variability. The result of this work is the retrieval of a methodological framework capable of determining and comparing the relevance of pollinators to pollen trasffer across plant species, which will be possible to link with theoretical models...
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The Competition Among Pollinators and the Impact of Managed Bees on Wild Pollinator Populations
Voldřichová, Alžběta ; Straka, Jakub (advisor) ; Štenc, Jakub (referee)
Pollinators play an important role in ecosystems. Their ties to plants are essential for the reproduction of many plant species and thus for the protection of species diversity. Pollinator species therefore need to be protected. But to protect them effectively, it is necessary to understand the relationships between pollinators. However, the interaction between pollinators is a complex topic that needs further research. One of the current threats to pollinator populations is commercial pollinator rearing. Commercially reared species, especially Apis mellifera and Bombus terrestris, have been introduced almost all over the planet due to their positive effects on crop yields and its by-products. Moreover, in their native ranges they are bred in much higher concentrations than would be possible without human intervention. But high concentrations of commercial pollinators do affect populations of wild ones. This thesis describes forms of pollinator competition and addresses the impact of commercially reared pollinators on wild pollinator populations. KEY WORDS: Honeybee - Bumblebee - Hoverfly - Nest usurpation - Pathogen transfer - Species protection - Invasive species
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