Positive association between the diversity of symbionts and parasitoids of aphids in field populations

Abstract

Parasites and pathogens are crucial in shaping immune systems. Many animals and especially insects have outsourced part of their immune function to protective symbionts. There is good evidence that, akin to immune systems, parasites shape the occurrence and diversity of protective symbionts and that likewise, protective symbionts can shape the occurrence and diversity of parasites. Such a relationship should result in a correlation between symbiont and parasite diversity in nature. Aphids are well known for possessing symbionts that provide specific and effective protection against parasitoid wasps. We compared symbiont and parasitoid diversity across multiple populations of different aphid species of the genus Aphis and their parasitoid wasps. The diversity of protective symbionts and parasitoids was indeed positively associated. Even though this association was very noisy, it is in line with the hypothesis that parasitoids and symbionts promote each other’s diversity. © 2021 The Authors.