MSc Student
Advisor: Jürg Schönenberger

Department of Botany and Biodiversity Research
University of Vienna

Abstract

The reproduction of most flowering plants (angiosperms), including about 75% of the world’s agricultural crops, depends on pollen transfer via animal vectors, making biotic pollination a key ecosystem service on which humans are highly dependent for nutritional security and welfare (Dicks et al., 2021; Vasiliev & Greenwood, 2023). Maintaining ecosystem functioning therefore depends on the conservation of pollinators. Among insect pollinators, wild bees, including bumblebees (Bombus spp.), are among the most important groups (Lima et al., 2022; Vasiliev & Greenwood, 2023). However, the biodiversity of insect pollinators, such as wild bees, has been declining over past decades: According to the European Red List of Bees, about 22,7% of Bombus species are currently threatened, with 36.4% of the species showing a declining population trend (Michez et al., 2026). In Austria, only half of the occurring 45 Bombus species are classified as “Least Concern” (LC), with the rest ranging between “Near Threatened” (NR) and “Critically Endangered” (CR) (Neumayer et al., 2024). This decline is largely driven by habitat loss and fragmentation caused by climate change, agricultural intensification, and urban development, which reduce the availability of suitable flowering plants and nesting sites essential for wild bee survival (Sikora et al., 2022; Brasil et al., 2024). While urbanization is recognised as a major driver of pollinator decline, urban landscapes have been shown to harbour diverse and abundant communities of native wild bees, especially bumblebees, often exceeding diversity of populations in adjacent rural landscapes (Hall et al., 2017). Urban green spaces containing flowering plants such as public parks, balconies, and flowerbeds can provide important resource patches (i.e., by offering pollen and nectar) for foraging wild bees (Hall et al., 2017). However, accessibility to these floral resources is limited by infrastructure separating the habitats and acting as barriers that restrict pollinator movement (Brasil et al., 2024). In addition, the use of non-native plants in these areas disadvantages oligolectic species that depend on nectar and pollen from specific native plants, reducing the overall availability of floral resources (Brasil et al., 2024; Michez at al., 2026). Therefore, increasing the connectivity and proximity of urban green spaces, as well as the use of appropriate native plant species, may enhance wild bee movement within cities and contribute to the stabilization of populations through increased gene flow (Graffinga et al., 2023). Such an approach has been implemented by the project “Wiener Biodiversitätskorridor” (Vienna biodiversity corridor) in Vienna, one of the most species-rich cities in Central Europe, harbouring around 70% of Austrias 702 wild bee species (Lanner et al., 2025; Kratschmer et al., 2021). The project, led by the University of Vienna, aims to support the urban pollinator biodiversity by implementing diverse flowerbeds alongside selected streets to act as stepping stones for pollinator insects, connecting small natural habitats within the city. It investigates the movement and foraging distances of selected wild bee species between the flowerbeds, the plant traits that attract them and the suitability of native plant species for urban environments (Naturschutzbund Österreich, 2025). A central component of the project is the “Sparkling Science 2.0” citizen science project “BiodiverCITY-Island Hopping”, in which students from five local schools help expand the biodiversity corridor by creating additional flowerbeds and participating in monitoring (University of Vienna, 2025). Embedded in the project, this master thesis focuses on the ecology of bumblebees (Bombus spp.) in Vienna. The movement of bumblebees between flowerbeds will be monitored to assess the role of flowerbeds in green space connectivity and their involvement in facilitating urban foraging. By combining these observations with the analysis of pollen from individual bumblebees, this thesis aims to participate in the understanding of bumblebee foraging ecology in a highly anthropogenic environment.