Bono, L. M. | bioRxiv Science

bioRxiv2026

Evolutionary reconstruction of bat influenza A viruses reveals segment-specific histories and host-associated selection

Influenza A (IAV) is a major zoonotic pathogen infecting a broad range of vertebrate hosts. In this study, we focus on inferring the evolutionary history of a subset of novel IAV, isolated from New World bats, which use a non-canonical host receptor and infer their relationship to sialic-acid-binding IAV. Little is known about when these novel subtypes emerged and how selection has acted upon them compared to sialic-acid-binding circulating strains. The current state of the field is split on whether bats are natural reservoirs for a distinct yet low abundance IAV lineage, or if influenza underwent rapid evolution after a recent spillover from a species within its standard host range. By analyzing segment-specific phylogenies, we hope to clarify the evolutionary history of bat IAV. Our objectives are to infer the date of divergence of non-canonical bat IAV from sialic-acid binding IAV, identify patterns of selection acting on bat IAV compared to representative samples of sialic-acid-binding IAV to identify potential signatures of genome-wide adaptation, and finally to reconstruct ancestral state transitions to infer which host taxa preceded spillover into bats. To accomplish this, we analyzed each IAV genome segment independently using least-squares molecular dating, Bayesian discrete-trait ancestral host reconstruction, and branch-site selection tests. Our results suggest that non-canonical bat IAV diverged from major IAV lineages 100-200 years ago, supporting a deeper evolutionary history rather than a very recent spillover event. However, discordance among genome segments in inferred divergence times, selective pressures, and ancestral hosts indicates that bat IAV experienced segment-specific evolutionary histories. Together, these findings suggest that non-canonical bat IAV represents a deeply divergent lineage with a complex evolutionary history involving segment-specific selection and host-transition dynamics.

microbiology↗

bioRxiv2019

Spatiotemporal dynamics of RNA virus diversity in a phyllosphere microbial community

Although metagenomics reveals that natural virus communities harbor vast genetic diversity, the spatiotemporal dynamics of viral diversity in the wild are seldom tested, especially across small geographic scales. This problem is usefully examined in the above-ground phyllosphere, because terrestrial plants are frequently infected by taxonomically-diverse RNA viruses, whose elevated mutation rates generate abundant allele diversity. Here, we studied the problem by comparative analysis of RNA virus samples over time from three spatially-separated patches of a common perennial legume, white clover (Trifolium repens L.), growing in a grassy lawn in Woods Hole Village (Falmouth, MA, USA). We predicted that clover samples would show similarly high levels of virus species (alpha) diversity across space, but differing among-patch diversity of non-dominant virus taxa over time (4 samples spanning 6 weeks). Results showed that recognizable alpha diversity in clover patches was consistently dominated by RNA virus family Alphaflexiviridae across space, but that all patches showed inconsistent spatiotemporal presence of a diversity of minority virus families. Also, we observed that white clover mosaic virus (WClMV) dominated all patches across space and time. The high coverage of WClMV fostered an haplotype analysis, which revealed that two strains of the virus consistently infected clover plants during the 6-week period.

microbiology↗