Environmental and habitat influences on the gut microbiota of two European pollinators

Pollinators are recognized as key contributors to crop pollination worldwide, and their recent decline has made pollinator conservation a critical challenge. In social insects, the gut microbial community is closely linked to essential functions such as longevity, fecundity, and overall health. This suggests that disruptions in microbial associations may significantly impair pollinator fitness. Flowers serve as a primary microbial source for pollinators, and the surrounding environment, particularly floral diversity, can strongly influence the composition of the microbiota in eusocial bees. It has been widely documented that bee biodiversity declines with increasing land-use intensity, leading to the loss of floral diversity and nesting sites. Therefore, the landscape can influence both the composition and diversity of pollinator microbiota. This study aims to investigate the role of several environmental factors, such as landscape, geolocation, and climate, in shaping the bacterial communities associated with two model European pollinators, Halictus scabiosae and Bombus pascuorum. The microbiota of specimens collected from different landscapes (agricultural and semi-natural sites) across five European countries (Italy, Switzerland, the Netherlands, Germany, and the UK) will be investigated using a meta-barcoding approach. The results will provide a comprehensive understanding of the ecological factors influencing pollinators’ microbiota composition and their subsequent impact on insect fitness. The insights gained will support the development of strategies aimed at enhancing microbial diversity in pollinators, indirectly improving their fitness, and contributing to biodiversity conservation with positive economic implications.