Predator niche overlap predicts effects on aphid vectors and a vector-borne virus

Multiple predator species can enhance or disrupt prey suppression based on whether different predators forage in complementary or overlapping niches. Interactions between predator species are primarily evaluated by resulting effects on prey abundance, although alterations of prey behavior also occur. When prey are vectors of plant pathogens, changes in their movement among plants may affect pathogen transmission as strongly as changes in vector abundance. Here, we assessed how single predator species, and pairs of species with varying degrees of niche overlap, affected pea aphid vectors and transmission of an aphid-borne pathogen, pea-enation mosaic virus (PEMV). Foliar-foraging predators reduced vector abundance but altered vector behavior in ways that promoted PEMV transmission, resulting in no net effects on PEMV prevalence. Predator pairings also enhanced vector suppression but caused vectors to move to parts of plants that were more susceptible to PEMV. Surprisingly, pathogen prevalence was only reduced in predator pairings that did not exhibit super-additive predation rates. Our study shows that enhanced predator consumption of vectors due to niche complementarity can affect pathogen transmission differently than it affects vector dispersal and feeding behaviors. Nonetheless, long-term suppression of vector populations may ultimately reduce pathogen transmission.