Vector-borne plant pathogens modify top-down and bottom-up effects on insect herbivores

Area of Science:

• Ecology
• Plant Pathology
• Entomology

Background:

• Ecological theory highlights host-plant traits influencing herbivore growth and predator-prey dynamics.
• Vector-borne plant pathogens can alter host plants and vectors, but their role as interaction modifiers in tri-trophic food webs is understudied.

Purpose of the Study:

• To investigate how a vector-borne plant pathogen, Pea-enation mosaic virus (PEMV), modifies bottom-up (plant-herbivore) and top-down (predator-prey) interactions.
• To assess the impact of PEMV-infectious pea aphids versus non-infectious aphids on trophic interactions within a manipulated food web.

Main Methods:

• Utilized a food web motif framework and a factorial experiment manipulating predator and plant communities.
• Compared trophic interactions involving PEMV-infectious pea aphids (Acyrthosiphon pisum) with non-infectious aphids.

Main Results:

• PEMV altered bi-trophic relationships, reducing vector performance and increasing predator susceptibility on some plant species.
• On other plant species, PEMV weakened top-down control or enhanced vector performance.
• Host-plant responses to PEMV varied, influencing herbivore abundance through altered performance and predator-prey dynamics.

Conclusions:

• Vector-borne plant pathogens act as significant interaction modifiers in plant-herbivore-predator dynamics.
• Host-plant responses to viruses can decrease herbivore abundance by reducing performance or increase it by weakening top-down control.
• Management of herbivore outbreaks requires consideration of the infection status of herbivore populations transmitting viruses.