Priority effects and habitat complexity affect the strength of competition

Area of Science:

• Ecology
• Marine Biology
• Behavioral Ecology

Background:

• Habitat complexity and priority effects are known to influence competitive interactions.
• The independent and synergistic effects of these factors on competition remain poorly understood.

Purpose of the Study:

• To quantify the independent and combined effects of priority effects and habitat complexity on intraspecific competition in coral reef fish.
• To understand how the timing of arrival and habitat structure affect fish survival and aggression.

Main Methods:

• A factorial field experiment was conducted in Moorea, French Polynesia.
• The study focused on recently settled individuals of the coral reef fish Thalassoma quinquevittatum.
• Survival, aggression, and habitat complexity were measured under different arrival timing scenarios.

Main Results:

• Simultaneous arrival of competitors increased survival 2.89-fold compared to delayed arrival (priority effect).
• Increased habitat complexity enhanced survivorship when arrivals were simultaneous but not when delayed.
• Survivorship was negatively correlated with aggression, which intensified when focal individuals arrived later than competitors.

Conclusions:

• Competition strength is context-dependent, varying with arrival timing and habitat complexity.
• Simultaneous arrival and complex habitats weaken competition and reduce predation, while delayed arrival increases aggression and negates complexity benefits.
• Habitat complexity primarily enhances survival by disrupting predation when competition is weak.