Imperfect diet choice reduces the performance of a predatory mite

Area of Science:

• Nutritional Ecology
• Predator-Prey Dynamics
• Behavioral Ecology

Background:

• The balanced diet hypothesis and toxin-dilution hypothesis predict consumers avoid low-quality food when high-quality food is present.
• Phytoseiulus persimilis, a predatory mite, can utilize Tetranychus urticae but performs poorly on T. evansi.

Purpose of the Study:

• To investigate the diet choice of Phytoseiulus persimilis when offered both high-quality (T. urticae) and low-quality (T. evansi) prey.
• To test predictions of the balanced diet and toxin-dilution hypotheses in this predator-prey system.

Main Methods:

• Assessing survival, development, and reproduction of P. persimilis on single prey types (T. urticae, T. evansi) and mixed diets.
• Evaluating the impact of prey quality on predator performance and the reversibility of negative effects.

Main Results:

• Juvenile P. persimilis had low survival on T. evansi; adults showed reduced reproduction and increased mortality.
• Mixed diets decreased predator performance, but negative effects of T. evansi were partially reversible.
• Crucially, P. persimilis consumed low-quality T. evansi despite the availability of high-quality T. urticae.

Conclusions:

• The observed feeding behavior contradicts both the balanced diet and toxin-dilution hypotheses.
• Including low-quality prey may increase overall fitness on ephemeral patches by maximizing reproduction over time, rather than focusing on immediate performance.