Testing the facilitation-competition paradigm under the stress-gradient hypothesis: decoupling multiple stress...

Area of Science:

• Ecology
• Marine Biology
• Environmental Science

Background:

• The facilitation-competition paradigm, under the stress-gradient hypothesis, suggests interactions shift from competition to facilitation with increasing environmental stress.
• Rigorous testing of this paradigm, especially across a full stress gradient, remains underexplored.
• Previous studies often focus on the switch point rather than the full spectrum of interaction changes.

Purpose of the Study:

• To conceptualize variations in interaction strength patterns along a stress gradient.
• To empirically evaluate temporal shifts in interactions between marine sessile animals under multiple stressors.
• To investigate the net effect of goose barnacles (Capitulum mitella) on mussel (Septifer virgatus) survivorship across varying physical and thermal stress levels.

Main Methods:

• Empirical evaluation of temporal interaction shifts between goose barnacles and mussels.
• Analysis of interaction strength along a combined stress gradient (physical disturbance and thermal stress).
• Separate analysis of the effects of physical disturbance and thermal stress on interaction patterns.

Main Results:

• The net effect of goose barnacles on mussel survivorship was positively correlated with the total stress gradient (physical and thermal).
• No negative interaction (competition) was observed, even under mild stress conditions.
• Individual stressor analysis showed a monotonic increase in positive effect with physical disturbance, but a quasi-asymptotic pattern with thermal stress.

Conclusions:

• The study highlights the importance of considering multiple and individual stress factors to understand the facilitation-competition paradigm.
• Observed interaction patterns differ from traditional predictions, emphasizing the need for integrative and mechanistic approaches.
• Findings underscore the complexity of ecological interactions and the necessity of detailed stressor analysis in marine environments.