Navigated range expansion promotes migratory culling

Abstract

SUMMARYMotile organisms can expand into new territories and increase their fitness1–6, while nonmotile viruses usually depend on host migration to spread across long distances7–9. In general, faster host motility facilitates virus transmission10. However, recent ecological studies have also shown that animal host migration can reduce viral prevalence by removing infected individuals from the migratory group11. Here, we use a bacteria-bacteriophage co-propagation system to investigate how host motility affects viral spread during range expansion. We find that phage spread during chemotaxis-driven navigated range expansion decreases as bacterial migration speed increases. Theoretical and experimental analyses show that the navigated migration leads to a spatial sorting of infected and uninfected host in the co-propagating front of bacteria-bacteriophage, with implications for the number of cells left behind. The preferential loss of infected cells in the chemotactic front inhibits viral spread. Further increase in host migration speed leads to a phase transition that eliminates the phage completely. These results illustrate that navigated range expansion of host can promote the migratory culling of infectious diseases in the migration group.