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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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Causes of bee loss (Anthophila) in the landscape
Bureš, Vít ; Straka, Jakub (advisor) ; Tropek, Robert (referee)
Bees (Anthophila) are one of the most important pollinators in the majority of Earth's biotopes. They interact with almost one-fifth of flowering plants and together with other pollinators they secure one- third of human food sources. Since the end of World war II,along-term decrease in numbers of bees and other insects is observed due to degradation of natural habitats, expansion of agriculture, pesticide usage, parasites, and infections. In North America and Europe, several studies reported a significant loss of bee diversity and abundance. The situation in tropics is unclear and there is not enough evidence if bees are threatened there. Specific changes in relation to the decrease of the bee population are observed in the case of honey bee (Apis mellifera). Due to human beekeeping activities and specific honey bee attributes such as bigger body size or tolerance to lower temperature, honey bees show different trends in their abundance than other bees. This study discusses the causes of these losses and possible future consequences, for example, the collapse of ecosystems as a result of pollination crisis or lack of human food. On the other hand, several phenomena such as extensive agriculture, green cities, or wildfires have a positive impact on bee abundance and diversity. This thesis presents...
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