Indirect facilitation between prey promotes asymmetric apparent competition.

Area of Science:

• Ecology
• Community Ecology
• Theoretical Ecology

Background:

• Apparent competition, where indirect interactions influence species dynamics, is crucial for understanding natural systems but remains empirically understudied.
• Investigating the mechanisms behind apparent competition is vital for comprehending its impact on ecological communities.

Purpose of the Study:

• To empirically evaluate the role of indirect trophic interactions in driving apparent competition within a controlled laboratory setting.
• To explore the dynamics of apparent competition using a model system with two prey species and a generalist predator.
• To identify mechanisms contributing to asymmetric outcomes in apparent competition.

Main Methods:

• A factorial experiment was conducted using two noncompeting prey species (Colpidium kleini and Chlamydomonas reinhardtii) and a generalist predator (Euplotes eurystomus).
• Structural equation modeling was employed to investigate the potential mechanisms underlying observed asymmetries in the interaction dynamics.

Main Results:

• The study revealed a significant role for positive interactions and indirect effects in generating asymmetric apparent competition.
• One prey species, Chlamydomonas reinhardtii, experienced an outcome favoring its persistence due to indirect facilitation and predator-induced defenses.
• Colpidium kleini indirectly benefited Chlamydomonas by consuming competing bacteria, while Chlamydomonas formed protective colonies against predation.

Conclusions:

• Asymmetric apparent competition may be more prevalent in natural ecosystems than previously suggested by classic theory.
• Understanding the mechanisms driving asymmetry in apparent competition is essential for advancing our knowledge of interspecific interactions and community dynamics.