Hologenomic structure of bacterial and fungal community composition in the West Nile virus vector Culex tarsalis

Background Microbiota play a crucial role in determining the ability for arthropod disease vectors to transmit pathogens. Microbial community structure can be heavily influenced by microbe-microbe interactions, host genetics and environmental factors. Here, we characterize the host population genetic structure, and bacterial and fungal communities in natural populations of the West Nile virus mosquito vector Culex tarsalis. Mosquitoes were collected and analyzed across the species range of the mosquito in the United States, where we used PoolRADSeq to quantify population genetic structure. Microbial community composition was characterized using bacterial 16S rRNA gene sequencing (V3-V4 region) and fungal ITS sequencing (ITS1 region).

PoolRADSeq identified four broad genetic clusters of mosquito populations, which corresponded to previous clusters identified by microsatellite analysis and RADSeq on individual mosquitoes. Microbiome diversity grouped mosquito populations into three broad clusters, with each cluster distinctively represented by diagnostic abundant bacteria (Ralstonia, Pseudomonas, or Zymobacter/Providencia, respectively). Clustering for fungal taxa was less pronounced. Geographic distance between populations was positively correlated with microbiome community dissimilarity, and multiple environmental factors were significantly correlated with microbial species richness and diversity.

These results suggest that bacterial and fungal communities are geographically structured in Cx. tarsalis, interact with important environmental factors, and are partially correlated with host genetic structure. As microbiota can affect the ability for mosquitoes to transmit pathogens, understanding the factors underpinning microbiome variation across space and time has important implications for the spread of vector-borne pathogens such as WNV. Competing Interest Statement The authors have declared no competing interest. Footnotes Added a figure (Fig 11) that had been mistakenly ommited in the original version.