A largely undescribed vertebrate virome in Antarctic wildlife reveals host, geographic, and seasonal structuring

Antarctica harbors a hidden virosphere that is still poorly characterized. Here, we used meta-transcriptomic sequencing to characterize the vertebrate-associated virome of 156 samples from eleven wildlife species collected across four Antarctic research stations between 2020 and 2023. With the identification of 43 putative novel species, we greatly expanded the known virosphere of Antarctic vertebrates. Most viruses were highly divergent and phylogenetically clustered with lineages associated with the corresponding host class, indicating broad host-linked evolutionary structure. Virome composition varied with host identity, sampling station, and season, with higher viral richness and abundance observed during austral spring and summer. Although most vertebrate-associated viruses were host restricted, a small subset was shared across host species, revealing limited but detectable cross-host connectivity. Notable discoveries included a highly divergent deltacoronavirus in cormorants and several deeply branching rotaviruses in penguins and seals. Together, these findings provide a baseline for tracking viral emergence and transmission in polar wildlife under increasing environmental and anthropogenic pressure.