Parasite‐manipulated host dispersal: evidence from population genetics and mark–recapture experiments

Host–parasite interactions are strongly influenced by the dispersal behaviour of both partners, yet direct evidence of parasite‐driven active suppression of host dispersal has been lacking. Here, we provide evidence that the parasitic nematode Sphaerularia bombi manipulates its hosts, bumble bee queens ( Bombus spp.), to limit dispersal. We conducted genetic analyses of S. bombi and its hosts in Japan and the Netherlands, and found pronounced genetic differentiation among local S. bombi populations, despite minimal structure among host populations, indicating that infected queens exhibit severely restricted movement. Mark–recapture experiments further confirmed that infected queens tend to remain near their hibernation sites. We also detected cryptic lineages within S. bombi , based on concordance between mitochondrial haplotypes and nuclear clades, suggesting weak host specificity. Our findings provide the first empirical demonstration that a parasite can actively constrain host dispersal – a strategy likely enhancing mating opportunities and local transmission at the cost of broader range expansion. Parasite populations are probably established through rare, accidental transport of infected hosts, leading to strong founder effects that may give rise to cryptic lineages even at small spatial scales. This work highlights a novel mechanism by which parasites can shape host movement ecology and drive evolutionary trajectories.