Convergence in Symbiont-Induced Plant-Mediated Responses to Herbivory: Cascading Effects for Foraging Parasitoids.

Convergent evolution arises when unrelated species develop similar traits without a shared ancestral origin possessing those characteristics. While typically observed at the organismal level, it can also occur at higher levels of biological organisation. Polydnaviruses represent a striking example of convergent evolution. These viruses, divided into bracoviruses and ichnoviruses, were independently acquired by braconid and ichneumonid parasitoid wasps respectively, to deliver pathogenic genes to caterpillar hosts. Here we show convergent patterns across trophic levels, demonstrating that both bracoviruses and ichnoviruses induce changes in plant-phenotypic traits that specifically benefit their parasitoid partners, facilitating plant-mediated host discrimination. This is achieved through an interaction network triggered by changes in the polydnavirus-infected herbivore (via alteration in regurgitant composition) which eventually affected parasitoids' foraging decisions. Our findings unveil a novel ecological benefit that polydnaviruses offer to their parasitoid partners through intricate, plant-mediated effects, providing evidence of convergence in symbiont-induced responses in terrestrial trophic systems.