Contrasting biodiversity-ecosystem functioning relationships in phylogenetic and functional diversity

Area of Science:

• Ecology
• Environmental Science

Background:

• Ecosystem functioning is known to be positively influenced by biodiversity.
• Traditional biodiversity-ecosystem functioning experiments often use species richness or phylogenetic relationships as diversity metrics.
• Theoretical and empirical evidence suggests functional diversity may be a more accurate predictor of ecosystem functioning.

Purpose of the Study:

• To investigate the relationship between different biodiversity metrics (species richness, phylogenetic diversity, functional diversity) and ecosystem functioning (biomass overyield).
• To assess how these relationships change with varying levels of species richness in an experimental setting.

Main Methods:

• An artificial biodiversity-ecosystem functioning experiment was conducted using 64 species of green microalgae.
• Microalgae were combined in mixtures ranging from two to 16 species.
• Biomass overyield was measured as an indicator of ecosystem functioning, alongside various biodiversity metrics.

Main Results:

• At low species richness, no significant correlation was found between overyield and functional or phylogenetic diversity.
• At high species richness (16 species), functional diversity positively correlated with overyield, while phylogenetic diversity showed a negative correlation.
• Phylogenetic and functional diversity were positively correlated with biomass overyield, primarily driven by their correlation with species richness at lower diversity levels.

Conclusions:

• Negative phylogenetic diversity-ecosystem functioning relationships can arise from interspecific growth inhibition.
• Functional diversity may better represent facilitative interactions, while phylogenetic diversity can reflect inhibitory ones at high species richness.
• Phylogenetic diversity is not always a reliable proxy for functional diversity, and low species richness experiments may underestimate negative species interactions.