Spatial scale influences taxon conservation in the eukaryotic virome of a mosquito

Our knowledge on the diversity of eukaryotic viruses has recently undergone a massive expansion. This diversity could influence host physiology through yet unknown phenomena of potential interest to the fields of health and food production. However, the assembly processes in eukaryotic viromes of terrestrial animals remain elusive. This situation hinders hypothesis-driven tests of virome influence on host physiology. Here, we explore virome assembly at different spatial scales in the eukaryotic virome of the mosquito Culex pipiens. This mosquito is a vector of human pathogens worldwide. Several new aspects of virome assembly were unveiled through a sampling involving five countries in Africa and Europe and large sample sizes. A group of viruses was conserved in C. pipiens populations in all countries. This core group represented a relatively large and diverse fraction of the virome. However, core viruses were not shared by all host individuals in a given country, and their infection rates fluctuated between countries and years. Moreover, the distribution of co-infections in individual mosquitoes suggested random co-occurrence of certain core viruses. We also observed differences in the virome depending on geography, with viromes tending to cluster depending on the continent. Thus, our results unveil that taxon conservation in a eukaryotic virome changes with spatial scale. Thus, predictions on virome assembly seem possible at a large geographical scale in C. pipiens. IMPORTANCEThe study of the eukaryotic virome of mosquitoes is an emerging research field. Beyond its fundamental interest, this field could lead to the development of control tools against the transmission of mosquito-borne human pathogens. However, we yet know little on the assembly patterns in the eukaryotic viromes of mosquitoes, as well as of terrestrial animals in general. This situation hampers the design of hypothesis-driven studies on the influence of the virome on pathogen transmission. Here, we have analyzed virome assembly in the mosquito vector Culex pipiens within and between countries in Africa and Europe. Our results show that integrating contrasted spatial scales allows to identify deterministic patterns in virome assembly. Such patterns can guide future studies of virome influence on mosquito physiology.