Cold and lonely: low microbial abundance and no core microbiota in mosquito populations across Greenland

Microbial symbionts are key players in insect ecology and evolution, but microbiota vary widely across and within host species. The microbiota of insect clades such as high-latitude mosquitoes remain understudied, despite their abundance and potential economic and medical relevance. Here, we resolve temporal and spatial variation in the abundance and diversity of bacteria and fungi associated with Ochlerotatus mosquitoes in Greenland. To this aim, we apply a comprehensive workflow combining the simultaneous characterization of host, bacterial, and fungal marker regions, contamination filtering, as well as bacterial quantification and joint species distribution modelling. We find that 573 mosquitoes collected in five regions of Greenland between 2009 and 2024 represented two species (O. nigripes and O. impiger). Their microbial communities were low-abundance, highly diverse, and dominated by environmentally versatile taxa, showing high individual-to-individual-rather than spatio-temporal variation, although taxa such as Pseudomonas and Serratia exhibited sex-specific associations. DNA from local vertebrates and potential vertebrate pathogens (e.g., Bartonella) was detected, likely reflecting blood meals. These findings suggest that Greenland Ochlerotatus mosquitoes do not rely on core microbiota, but engage in flexible associations with diverse, low-abundance microbial communities. They also point to mosquitoes as likely vectors of bacterial and fungal pathogens in the Arctic.