Effects of a plant virus on community dynamics in peas

The transmission of a plant virus through a population of susceptible hosts is governed by several ecological factors. Plant viruses often manipulate the behavior and physiology of their hosts and vectors in order to promote dispersal. Phytophagous insects also influence the physiology of their host plant by inducing a wide range of chemical defenses. Although it is well established that the fitness and selection behavior of polyphagous insects is heavily influenced by prior herbivory, little is known about the role these herbivore-induced changes may be playing in influencing the spread of a plant virus. To this end, we conducted several behavioral and fitness assays to examine how both viruliferous and non-viruliferous vectors responded to plants subjected to a priori non-infective herbivory, using pea (Pisum sativum), the pea aphid (Acyrthosiphon pisum), and pea enation mosaic virus (PEMV) as a model pathosystem. While non-viruliferous aphids experienced decreased fitness on previously herbivorized hosts, aphids carrying the virus experienced a fitness boost on herbivorized hosts. Similarly, while non-viruliferous aphids were more likely to disperse away from an herbivorized host, viruliferous aphids were more likely to remain stationary on herbivorized plants. Consequently, prior herbivory suppressed the transmission of PEMV in experimental plots. This result indicates an interaction effect between herbivory and viral infection, though the exact mechanism(s) underlying this interaction remain unknown.