Dynamics of microbial enrichment in adult butterflies

• Applicant: Dr. Arne Weinhold
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Microbial Ecology and Applied Microbiology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546907793

The assembly of a specialized gut-microbiota is important for the health of pollinating insects. Eusocial species like honey and bumble bees can rely on an early acquisition via social transmission. But most wild pollinators are solitary and need to acquire microbes from the environment with each generation. Still, major drivers of the solitary pollinator microbiota are insufficiently understood. In our previous study, we discovered that adult butterflies of Pieris brassicae accumulate high amounts of microbes, which exceeds the quantities observed in honey bees. This contrasts with the larvae, which do not accumulate nor require a resident gut-microbiota. Pieris butterflies are multivoltine and have multiple generations per year. Our functional investigations of the adult microbiota reveled a transgenerational phenotype on the offspring. A disturbance of the adult microbiota influenced immune parameter in the larval offspring and impaired their ability to perform a host plant switch. Such a trans-generational microbiome function raises questions about the driver of microbiota assembly for each adult generation. Current data suggests a host-specific enrichment, but this has never been tested within natural populations. Within this project, I want to fill this gap of knowledge and investigate how the microbiota acquisition, assembly and accumulation process of adult butterflies can be disturbed in nature. The work is divided into three work packages outlined as follows: (I) Resolving microbial accumulation dynamics of each adult generations within a year. (II) Testing the assumption of host selection by applying a neutral community model following microbiota assembly over time. (III) Empirical microbiota manipulation experiments to test how timing and order of microbial acquisition in adults influences offspring performance. The main focus will be on the temporal progression of microbiota enrichment in three consecutive adult generations, to connect phenology with microbial abundance. The combination of molecular investigations and ecological modelling will allow to test hypothesis about host-selection and neutral community assembly in natural habitats. This will be accompanied by empirical tests within a rearing, to evaluate how a disturbance in microbial acquisition can influence the accumulation process. The combination of quantitative and qualitative microbiota analyses will lead to a better understanding of the balance between stochastic and deterministic processes shaping the adult butterfly microbiota in natural habitats. This study will be the first systematic investigation of the adult butterfly microbiota within Europe and will provide fundamental insights about transgenerational microbiome function. This provides a basis for further investigations how habitat fragmentation could negatively impact microbial transmission across plant-pollinator networks.

• DFG Programme: Research Grants