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Picture: The photo shows a grove hoverfly, Latin Episyrphus balteatus, sitting with spread wings on a yellow flower and taking nectar.

Pollinators contribute to biodiversity and are vital for ecosystem functioning. In the last decades, a global decline of pollinator species and individuals has been observed. In intensively used agricultural areas, pollinators suffer from habitat loss and fragmentation, exposure to pesticides and declining food sources. Thus, land-use intensity represents a major threat for pollinators in such landscapes. These stressors can affect pollinator health, resulting in developmental changes (e.g., wing asymmetry), physiological changes (change of pheromone composition) or increased viral loads. In return, such changes in pollinator health may cause changes of foraging activity or behaviour, what can ultimately result in a loss of pollination services. Therefore, it is important to disentangle the links between land-use intensity, pollinator health and pollination services in order to preserve pollination services and ecosystem functioning in our agricultural landscapes.


In this project we pursue two major goals: (I) identification of the effects of land-use intensity on pollinator health and (II) disentangle how connections of land-use and pollinator health affect pollination services. We will focus on two species, Bombus lapidarius and Episyrphus balteatus, which represent two major pollinator groups: bumble bees and syrphid flies. For this purpose, we will collect field data on pollinator health and pollinator behaviour of the pollinator species in the grassland plots of the exploratories and conduct lab- and common garden experiments.

Picture: The photo shows a young scientist on a grassy hill on a summer's day, swinging a landing net to catch pollinating insects. Flowers with yellow blossoms grow between the tufts of grass. Individual bushes and groups of trees can be seen in the background.
Landing net catches of pollinators

We will analyse the effects of land-use intensity on several pollinator health indicators, such as asymmetric wing development, body size, viral loads and composition of cuticular pheromones. For the analysis we will use the land-use index (LUI), pesticide use, data on plant abundance and diversity, and land cover types in the surrounding as surrogates for land-use intensity.

Hypotheses

  • Viral loads and asymmetric wing development are positively correlated with increasing land-use intensity.
  • The amount of cuticular pheromones decreases and their composition changes with increasing land-use intensity.

Methods

Up to ten individuals of B. lapidarius and E. balteatus will be collected in all 150 grassland plots of the exploratories and analysed for pollinator health indicators. In a fully-crossed two-factorial labour experiment we will simulate different intensities of land-use by exposing the pollinator species to different diets and pesticide amounts to identify underlying mechanisms between land-use intensity and pollinator fitness.

Picture: The photo shows a stone bumblebee, Latin Bombus lapidarius, hanging on a pink meadow clover flower and taking nectar
Bombus lapidarius

To disentangle links between land-use intensity, pollinator health and pollination services, we will conduct pollen analysis and observations on pollinator behaviour.

Hypotheses

  • The amount of collected pollen decreases and its composition changes with increasing land-use intensity and decreasing pollinator health.
  • Foraging behaviour changes and pollinator efficiency decreases with increasing land-use intensity and decreasing pollinator health.

Methods

We will conduct analysis on pollen amounts and diversity with the pollinator individuals collected in the field. Additionally, we will perform observations on pollinator behaviour in all grassland plots of the exploratories. Amongst others, we will examine the visit duration, flight distance between two plant individuals and floral constancy (number of plant species visited in a certain period). In common garden experiments, we will make observations on pollinator behaviour of B. lapidarius und E. balteatus in flight cages under simulation of different land-use intensities to uncover causal correlations between land-use, pollinator health and pollination services.

Picture: The photo shows a grove hoverfly, Latin Episyrphus balteatus, sitting with spread wings on a yellow flower and taking nectar.
Episyrphus balteatus

To determine whether the correlations between pollinator health and land-use intensity are constant over time, B. lapidarius and E. Balteatus individuals from previous projects are used (2008 and 2012), ‘Arthropods II: Pollinators’ and ‘Response’, PI: Blüthgen and ‘Landscapes’, PI: Westphal) and compared with the currently collected data. Here we focus on the analysis of asymmetric wing development and body size as indicators of pollinator health.

Hypotheses

  • Wing asymmetry is positively and body size negatively correlated with increased land-use intensity.
  • Relationships between land-use intensity and pollinator health are constant over time, e.g. increased land use results in decreased pollinator health.
Picture: The diagram contains information on the work steps involved in recording pollinator health and pollination performance of captured specimens of stone bumblebees, Latin Bombus lapidarius, and grove hoverflies, Latin Episyrphus balteatus. Work step 1 is the analysis of wing asymmetry between the right and left forewing of the animals. Step 2 is the analysis of total virome as well as the prevalence of selected viruses. Step 3 is, for Bombus lapidarius, the analysis of cuticular pheromones of all individuals. Step 4 is analyses of the amount and diversity of carried pollen. Step 5 is the observation of pollinator behaviour on all grassland plots.
Workflow for the assessment of pollinator health and pollination performance. For all captured individuals of B. lapidarius and E. balteatus, respectively, the wing asymmetry between left and right forewing of the animals (1) and the total virome as well as the prevalence of selected viruses (2) are analysed as indicators of pollinator health. In the case of B. lapidarius, the cuticular pheromones of all individuals are additionally analysed (3). In order to identify correlations between land use intensity and pollination performance, analyses on the amount and diversity of pollen carried are performed with the pollinator individuals captured in the field (4). In addition, the behaviour of pollinators on all grassland plots is observed (5).

Doc
Landnutzung beeinflusst das Bestäuber-spezifische Nahrungsangebot und das Bestäuberverhalten
Birkenbach M., Straub F., Kiesel A., Ayasse M., Wilfert L., Kuppler J. (2024): Land-use affects pollinator-specific resource availability and pollinator foraging behaviour. Ecology and Evolution 14 (3), e11061. doi: 10.1002/ece3.11061
More information:  doi.org
Doc
Auswirkungen von Nahrungsqualität und Insektiziden auf individuelle und koloniebezogene Gesundheitsmerkmale einer häufigen Bestäuberart, Bombus terrestris
Straub F., Birkenbach M., Leonhardt S. D., Ruedenauer F. A., Kuppler J., Wilfert L., Ayasse M. (2023): Land-use associated stressors interact to reduce bumblebee health at the individual and colony-level. Proceedings of the Royal Society B 290: 20231322. doi: 10.1098/rspb.2023.1322
More information:  doi.org
Doc
Effekte von Landnutzung auf die Bestäubergesundheit
Straub F. (2023): Effects of land-use stress on pollinator health. Dissertation, Ulm University
More information:  oparu.uni-ulm.de
Doc
Landnutzung führt zu Veränderungen im Duftbouquet und der Morphologie in Bombus lapidarius
Straub F., Kuppler J., Fellendorf M., Teuscher M., Vogt J., Ayasse M. (2022): Land-use stress alters cuticular chemical surface profile and morphology in the bumble bee Bombus lapidarius. PLOS ONE 17 (5): e0268474. doi: 10.1371/journal.pone.0268474
More information:  doi.org

Scientific assistants

Prof. Dr. Manfred Ayasse
Project manager
Prof. Dr. Manfred Ayasse
Universität Ulm
Dr. Jonas Kuppler
Project manager
Dr. Jonas Kuppler
Universität Ulm
Prof. Dr. Lena Wilfert
Project manager
Prof. Dr. Lena Wilfert
Universität Ulm
Markus Birkenbach
Employee
Markus Birkenbach
Universität Ulm
Florian Straub
Alumni
Florian Straub
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