Revealing how species loss affects ecosystem function: the trait-based Price Equation partition

Area of Science:

• Ecology
• Ecosystem Science
• Theoretical Ecology

Background:

• Species loss significantly alters ecosystem functions, such as primary production.
• The Price Equation partition framework quantifies effects of species loss on ecosystem function, categorizing them into species-richness effect (SRE), species-composition effect (SCE), and context-dependence effect (CDE).
• Existing frameworks do not fully explain the determinants of individual species' functional contributions.

Purpose of the Study:

• To extend the Price Equation partition by incorporating species' traits to better understand how species loss affects ecosystem function.
• To re-express the species-composition effect (SCE) and context-dependence effect (CDE) in a trait-based manner.
• To investigate the relative importance of trait-based SCE and CDE in altering ecosystem function following species loss.

Main Methods:

• Developed a trait-based Price Equation partition using multiple regression to link species' traits to their functional contributions.
• Applied the trait-based framework to empirical data from grassland plant communities and protist microcosm food webs.
• Introduced "synecological" traits to account for context-dependent effects arising from interspecific trait variation.

Main Results:

• In both grassland and protist studies, post-loss changes in the relationship between species' traits and their functional contributions (trait-based CDE) had a greater impact on ecosystem function than the nonrandom loss of species with specific traits (trait-based SCE).
• The protist microcosm data demonstrated that species loss can alter the "diet uniqueness" of remaining species, contributing to context dependence.
• Trait-based CDE was identified as a key driver of ecosystem function alterations following species loss.

Conclusions:

• The trait-based Price Equation partition provides a more mechanistic understanding of how species loss impacts ecosystem function.
• Changes in the relationship between species traits and their functions are critical drivers of ecosystem change, often surpassing the direct effects of losing specific species.
• This framework is applicable to complex ecological communities, including those with interdependencies between species traits.