Eco-evolutionary strategies drive viral diversification in nutrient-poor soils across elevation gradients.

As global change intensifies, understanding the eco-evolutionary trade-offs among soil viral communities and the maintenance of their functional traits across environmental gradients is crucial for predicting soil health and ecological functions. Yet how viral communities respond to environmental change remain poorly understood. Using metavirome sequencing along an elevation gradient, which serves as an ideal proxy for environmental variations, we reveal the extensive diversity of viruses and expand the information on soil viruses in Africa. Compared to climate pressures associated with increasing elevation, nutritional constraints driven by higher elevation were more closely associated with significant differentiation in viral populations, mainly driven by an increase in both lytic viruses and functional diversity. These findings were consistently supported by field microcosm experiments on the same mountainsides and the global data sets from other mountain regions. With increasing elevation, phages undergo greater diversifying selection, encoded more bacterial life history strategy genes associated with stress tolerance and ruderals/opportunist, and had a higher proportion of unannotated functions, potentially playing a role in host carbon assimilation in nutrient-poor environments. These findings provide insights into the biogeography and ecological roles of viruses and serve as a foundation for understanding the response of soil viruses to global change.