The interplay between density- and trait-mediated effects in predator-prey interactions: a case study in aphid wing...

Area of Science:

• Ecology
• Evolutionary Biology
• Entomology

Background:

• Natural enemies impact prey populations through direct predation and by inducing changes in prey traits.
• Non-lethal effects are crucial for prey population dynamics, but their interaction with density-mediated effects is poorly understood.

Purpose of the Study:

• To investigate the relationship between predation rate, prey density, and trait modification in aphid-predator interactions.
• To understand how natural enemies' density-mediated and trait-mediated effects interact to influence prey population dynamics.

Main Methods:

• Two experiments were conducted using pea aphids (Acyrthosiphon pisum) and their natural enemies, hoverfly larvae (Episyrphus balteatus) and lacewing larvae (Chrysoperla carnea).
• Wing induction in pea aphids was measured as a function of predation rate under varying prey densities.

Main Results:

• Both hoverfly and lacewing larvae significantly increased the production of winged morphs in pea aphid offspring.
• Aphid wing induction showed a strong response at medium predation rates, with weaker responses at very high or very low rates.
• Wing induction was influenced by the interplay between predation rate and resulting prey density.

Conclusions:

• Wing induction in pea aphids is a general response to the presence of natural enemies.
• Density-mediated and trait-mediated effects of natural enemies are interconnected.
• These combined effects jointly regulate the impact of natural enemies on prey population dynamics.