Evolution in Fast-Forward: How Migration Accelerates Viral Change

Viruses do not always evolve rapidly, even during massive outbreaks. Yet when they encounter a new community with new hosts, they can evolve quickly. Researchers from the Cluster of Excellence "Balance of the Microverse" at the Friedrich Schiller University Jena, Utrecht University, and the Max Planck Institute for Evolutionary Biology in Plön have identified this striking contrast in garden compost ecosystems grown under controlled laboratory conditions. The findings, published in Science Advances, show that evolutionary dynamics can change drastically in experiments that incorporate realistic ecological conditions.

Exceptionally large viral blooms

The team studied bacteriophages—viruses that infect bacteria—in microbial communities collected from a common garden compost heap. In some communities, they observed enormous viral blooms of a previously undescribed bacteriophage. At its peak, the bacteriophage accounted for 74 percent of all genetic material in the compost samples, making it the largest bacteriophage outbreak documented to date. "We were genuinely surprised to see a single virus completely dominating such a complex ecosystem,“ says first author Jeroen Meijer, a postdoc at the Microverse Cluster. "Viruses have very small genomes compared to cellular organisms, so we expected to find only modest amounts of viral DNA."

Migration breaks evolutionary stasis

Despite these enormous blooms, the virus showed surprising genomic stability. This contrasts with the common expectation that viruses and their hosts undergo rapid co-evolution, where hosts evolve resistance and viruses counter-adapt. Instead, the virus remained essentially unchanged throughout the year-long experiment.

The picture changed dramatically when the team allowed the viruses to migrate between different compost communities. Migration acted like an evolutionary turbocharger: as soon as the virus was introduced into a new microbial community, it began to evolve in fast-forward. These changes were concentrated in genes involved in host recognition and infection, consistent with adaptation to new bacterial targets. "Migration mixed previously isolated viral populations, and exposed the virus to new bacterial communities“ explains Bas E. Dutilh, Professor of Viral Ecology and Omics. “Once the virus encountered new potential hosts, evolution accelerated immediately“.

Broader implications

The findings underscore how much viral evolutionary dynamics can differ, depending on their migration and the interconnectivity and complexity of their host communities. Capturing this complexity may be key to understanding how microbial ecosystems respond to environmental disturbance — and to anticipating the consequences of viral evolution in applied contexts, such as phage therapy, where the diverse, shifting microbial landscape of a patient's microbiome may drive viral evolution in ways that closed systems cannot predict.

Orginal Publication:

Jeroen Meijer et al., Eco-evolutionary dynamics of massive, parallel bacteriophage outbreaks in compost communities.Sci. Adv.12,eaeb8246(2026). DOI:10.1126/sciadv.aeb8246