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Picture: The photo shows a pollen-laden Earth Bumblebee, Latin Bombus terrestris, flying into an orange-red poppy flower hanging downwards. There are drops of water on the leaves of the flower. Green ears of grain can be seen in the background.

Interactions between bees and flowering plants form a ‘famous’ and evolutionary ‘old’ mutualism, which can largely determine the reproductive fitness of both bees and plants. The structure, stability and fitness outcomes of this mutualism largely depend on the diversity and composition of the interacting community which can be severely altered by land-use. In fact, partner and interaction diversity typically decrease with increasing land-use intensity. Interestingly, few studies have experimentally addressed the effect of land-use change and thus community alterations on the relationship between interaction network dynamics and mutualistic outcomes of interaction partners.

MacroBEEs aims at filling this knowledge gap by building upon existing knowledge on correlative effects between land-use intensity and bee-plant interactions. We now want to use the established plot framework as well as the new experimental design to gain a better mechanistic understanding of this mutualistic relationship by differentiating between effects of land-use components and landscape context on the reproductive success and thus mutualistic outcome of both partners.


We will investigate

  1. how land-use driven changes in plant community composition and diversity affect visitation patterns and foraging choices of wild and managed bees,
  2. how the bees’ foraging choices affect constancies or changes in the nutritional and taxonomic composition of composed diets and subsequently health and fitness of wild and managed bees, and finally
  3. how alterations in bee foraging decisions and thus visitation patterns affect pollen transfer and seed set in plants and thus pollination success.
Picture: The photo shows a captured, living mason bee in a transparent plastic tube with blue printed graduations, which is held horizontally in front of the camera. In the background meadow soil can be seen.
A mason bee (genus: Osmia)

To tackle these questions, we will combine field observations, DNA metabarcoding of pollen from bees and plant stigmas, chemical analyses of pollen and dietary experiments with three focal bee species in the lab, and we will analyze data using network parameters and statistical modeling.


During the previously funded project MicroBEEs, which was also part of the Biodiversity Exploratories, we investigated the effect of land-use intensity on the interaction between trap nesting bee species, resources and the bees’ microbiota. Results reveal novel insight into the factors determining changes in the bees’ microbial communities and how they are related to land-use driven alterations of floral and nesting resources. Besides effects on the bees’ microbiota, MicroBEEs further showed a strong impact of land-use intensity on a) the diversity and community composition of trap nesting bees (directly sampled at plots), b) the diversity and composition of plant species visited for pollen collection/in larval food of trap nesting bee species, and c) the nutrient content of larval food.


Doc
Bare soil spots in grasslands in relation to wildbee richness and abundance
Nackte Bodenstellen im Grasland in Bezug auf Wildbienenreichtum und -reichtum
Härtl F. (2023): Bare soil spots in grasslands in relation to wildbee richness and abundance. Master thesis, TU München
Doc
Land-use intensity effects on intraspecific variation of pollination-associated floral traits in four typical grassland species
Auswirkungen der Landnutzungsintensität auf die intraspezifische Variation von bestäubungsassoziierten Blütenmerkmalen bei vier typischen Grünlandarten
Höwener A. S. (2022): Land-use intensity effects on intraspecific variation of pollination-associated floral traits in four typical grassland species. Master thesis, TU München
Doc
Leonhardt S. D., Peters B., Keller A. (2022): Do amino and fatty acid profiles of pollen provisions correlate with bacterial microbiomes in the mason bee Osmia bicornis? Philosophical Transactions of the Royal Society B 377 (1853): 20210171. doi: 10.1098/rstb.2021.0171
More information:  doi.org
Doc
Heterospecific pollen assessment on Ranunculus stigmas using DNA metabarcoding
Preussner A. (2022): Heterospecific pollen assessment on Ranunculus stigmas using DNA metabarcoding. Bachelor thesis, Ludwig Maximilian University of Munich
Doc
Automatization Process of Landscape Heterogeneity Index for Biodiversity Exploratories
Automatisierungsprozess des Landschaftsheterogenitätsindex für Biodiversitätsexploratorien
Arisoy B. (2022): Automatization Process of Landscape Heterogeneity Index for Biodiversity Exploratories. Master thesis, TU München
Doc
Effects of Land-use Intensity on Pollen Diversity in Brood Cells of Osmia Bicornis A Light Microscopic Study of Pollen
Auswirkungen der Landnutzungsintensität auf Pollen Vielfalt in Brutzellen von Osmia Bicornis Eine lichtmikroskopische Untersuchung von Pollen
Seiler R. (2022): Effects of Land-use Intensity on Pollen Diversity in Brood Cells of Osmia Bicornis. Master thesis, TU München
Doc
Einfluss verschiedener Bewirtschaftungsintensitäten von Grünland auf die Blütenbesuchsmuster von Wildbienen und Honigbienen – Eine Untersuchung auf den Standorten der Biodiversitäts-Exploratorien in Deutschland
Borchardt R. (2021): Einfluss verschiedener Bewirtschaftungsintensitäten von Grünland auf die Blütenbesuchsmuster von Wildbienen und Honigbienen - Eine Untersuchung auf den Standorten der Biodiversitäts-Exploratorien in Deutschland. Master thesis, TU München

MacroBEEs will directly build upon these insights and complement them with dedicated sampling and analyses according to the hypotheses. As further data on bee-plant interactions is available for previous funding periods (since 2008), we can extend our analyses to a period of 15 years, which provides the unique opportunity to assess long-term effects of land-use on variability in the network structure, stability, link symmetries and resilience of this important mutualistic interaction. By further adding insight into functional/reproductive outcomes MacroBEEs will greatly enhance our understanding of how pollination interaction networks respond to land-use intensification in terms of functional resilience and the probability of extinction and thus link losses, but also of ultimate consequences, such as the stability of pollination within plant communities.

Scientific assistants

Prof. Dr. Sara Leonhardt
Project manager
Prof. Dr. Sara Leonhardt
Technische Universität München (TUM)
Prof. Dr. Alexander Keller
Project manager
Prof. Dr. Alexander Keller
Ludwig-Maximilians-Universität - LMU München
Susanne Werle
Employee
Susanne Werle
Technische Universität München (TUM)
Dr. Fabrice Requier
Employee
Dr. Fabrice Requier
Technische Universität München (TUM)
Stephanie Boese
Alumni
Stephanie Boese
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