Functional Traits Predict Outcomes of Current and Novel Competition Under Warmer Climate

Area of Science:

• Ecology
• Plant Biology
• Climate Change Research

Background:

• Functional traits can help predict plant community responses to competition under climate change.
• Understanding current and novel competition is crucial for forecasting species interactions and coexistence.
• The role of functional traits in predicting competition outcomes across environmental gradients remains unclear.

Purpose of the Study:

• To investigate how functional traits predict competition outcomes (current and novel) across an elevation gradient.
• To assess the influence of environmental context on trait-based predictions of plant competition.
• To determine if functional traits can forecast competitive interactions involving species not currently interacting.

Main Methods:

• Experimental interaction of high- and low-elevation plant species pairs across three Swiss Alps sites.
• Quantification of population-level competition outcomes (invasion growth rates), fitness differences, and niche overlap.
• Measurement of 15 functional traits for each species and correlation with competition metrics.

Main Results:

• Trait associations with competition were stronger at lower elevations, linked to greater fitness differences.
• Trait predictability decreased at higher elevations, suggesting environmental context influences trait function.
• Novel competitors exhibited greater niche overlap than current competitors, intensifying competitive effects.
• Functional trait differences generally predicted outcomes for both current and novel competitors effectively.

Conclusions:

• Functional traits are valuable for predicting plant competition, but their predictive power is context-dependent.
• Climate warming may exacerbate competitive exclusion due to amplified fitness differences at lower elevations.
• Traits can forecast interactions between species not yet in contact, aiding in predicting future community dynamics.