Low variability in the capsid gene of a generalist densovirus across lepidopteran hosts and geographic regions

Viruses are ubiquitous in all ecosystems, and insects can serve as model host systems for understanding their geographic range and host specificity. Lepidoptera are relatively easy to collect and rear and are known to harbor diverse groups of viral pathogens. Much of the research on viruses in Lepidoptera has focused on baculoviruses, but this is beginning to change with better sequencing techniques. In this study, we use genetic tools to characterize the host and geographical range of the Junonia coenia densovirus (JcDV) (Family Parvoviridae, subfamily Densovirinae, genus Protoambidensovirus, specific epithet lepidopteran1). Using host tissue and larval frass, we screened 25 lepidopteran families from 11 locations across North and Central and South America for JcDV. We detected JcDV in the frass from 11 families of Lepidoptera, originating from both Neotropical and Nearctic biogeographic realms. To characterize genetic variation in the viruses detected, we conducted Sanger sequencing of a segment of the viral capsid gene in ten frass samples and from an additional 56 individual lepidopteran cadavers from three families in the Papilionoidea superfamily. Across all sequences obtained, the average sequence identity to the Oxford reference genome sequence was 99.85% and within our samples 99.77%. Compared to the reference, we found 18 nucleotide changes which were characterized into ten JcDV haplotype variants. These differences conferred seven amino acid substitutions and were not predicted by sample type (frass or cadaver tissue), geographic location, or lepidopteran host family. Ultimately, we conclude that JcDV is a widespread virus to which many lepidopteran families are exposed in their natural environment, and the capsid gene of JcDV is genetically well-conserved across geographic space and lepidopteran host species.