[Thesis defence] 18/12/23, Clémentine Leroy: "Sensitivity of wild bees to landscape changes in agroecosystems". (UR 406 Bees & Environment, INRAE)

Title of the thesis

Eco-extraction of high added-value biomolecules from olive pomace

Date and place

18 December 2023 at 1.30 pm, Campus Jean-Henri Fabre, CERI, Amphi Blaise

Discipline

Agronomic Sciences, Population Biology and Ecology

Laboratory

UR 406 Bees & Environment, INRAE

Framing

• Cédric Alaux
• Mickael Henry
• Jean-Luc Brunet

Composition of the jury

• Alice Michelot-Antalik: rapporteur
• David Giron: rapporteur
• Maryse Vanderplanck: examiner
• Isabelle Dajoz: examiner
• Mickael Henry
• Jean-Luc Brunet

Summary of the thesis

The current context of the decline of various wild bee species raises the need to find and reflect on more proactive and relevant conservation and restoration measures. In this context, the use of measurements of the vitality and body condition of organisms could represent an interesting opportunity to assess how they respond to environmental changes. We hypothesised that physiological changes could provide information on the individual sensitivity of bees to environmental change and act as indicators of habitat quality. These physiological measures are very promising and already show examples of success for many species subjected to various environmental disturbances, namely environmental pollution, climate change and landscape resources. With this in mind, we applied this ecophysiological approach to measure the effects of the availability and richness of floral resources on the body condition of various wild bee species. In our work, bee body condition is a compilation of body mass and nutritional status indicators (protein, triglyceride and glycogen concentrations).

We began by examining the influence of semi-natural features (temporary and permanent grassland, set-aside and wooded heathland) and hedgerows on the reproductive success and body condition of the mason bee (Osmia cornuta) in apple orchards. Semi-natural habitats and hedgerows in orchards did not affect osmia reproduction, but did have beneficial effects on the weight and protein content of the offspring, probably due to the greater diversity of pollen harvested. At the same time, we tested the effect of a land-use index (compilation of farmers' practices including mowing, grazing and fertilisation) and floral diversity on wild bee communities in grassland areas, focusing on bumblebees. The weight of bumblebees particularly decreased with the intensity of grassland management in a species forming small colonies (Bombus sylvarum), while other species were unaffected. Protein concentrations (particularly in Bombus terrestris) and glycogen also varied according to grassland management practices, with these variations being conditioned by the length of the species' proboscis. This work shows that measures of body condition can be useful in improving our understanding of the responses of wild bees to habitat quality. In particular, measurements of body mass and protein content seem to be of particular interest for attesting individual sensitivity. Acquiring this knowledge and putting it into practice, in conjunction with other disciplines (behavioural ecology, social sciences, epidemiology, etc.) and with those involved in protecting pollinators, could help to refine and co-construct strategies for conserving wild bee populations in order to combat the decline in bee numbers.