# Aphid Parasitoid Mothers Don't Always Know Best through the Whole Host Selection Process

## TL;DR

Aphid parasitoids prefer certain plants for laying eggs, but their choices don't always lead to the best outcomes for their offspring.

## Contribution

The study reveals a disruption in parasitoid host selection behavior in complex plant-aphid systems.

## Key findings

- Parasitoids preferred the C. sativa-A. fabae complex but oviposited more in aphids on V. faba.
- Parasitoids that developed on the V. faba-A. fabae complex showed better fitness.
- Host selection behavior may be disrupted in complex habitats.

## Abstract

Parasitoid host selection behaviour has been extensively studied in experimentally simplified tritrophic systems formed by one single food chain (one plant, one herbivore and one parasitoid species). The "Mother knows best" hypothesis predicts that the preference for a plant-host complex should be positively correlated with plant quality for offspring performance. We studied the host selection behaviour of the generalist endoparasitoid Aphidius matricariae towards the black bean aphid Aphis fabae in the intercrop system including Vicia faba as a focal plant and its companion plant Camelina sativa. Dual-choice laboratory bioassays revealed that parasitoid females preferred to orientate towards (1) the plant-aphid complex over the non-infested plant whatever the complex (2) the C. sativa-A. fabae complex over the V. faba-A. fabae complex. In dual choice attack rate bioassays, parasitoid females showed more interest towards the aphids on C. sativa but paradoxically chose to oviposit more in aphids on V. faba. Ultimately, parasitoids that had developed on the V. faba-A. fabae complex exhibited better fitness parameters. By demonstrating that parasitoid females were able to discriminate the aphid host that offered the highest fitness to their offspring but selected beforehand the least suitable plant-aphid complex, we provide key insight into the disruption in their host selection behaviour potentially triggered by diverse habitats. This suggests that the "Mother knows best" hypothesis could be thwarted by increasing the complexity of the studied systems.