Rare species support vulnerable functions in high-diversity ecosystems

Area of Science:

• Ecology
• Conservation Biology
• Biodiversity Research

Background:

• Human activities are driving a sixth mass extinction, with rare species disappearing first.
• The role of rare species in maintaining ecosystem functions, especially in species-rich ecosystems, remains debated.
• High functional redundancy in diverse ecosystems is assumed to buffer against species loss.

Purpose of the Study:

• To investigate the role of rare species in supporting ecosystem functions across diverse ecosystems.
• To determine if common species can compensate for the loss of functions provided by rare species.
• To assess the functional vulnerability associated with rare species in highly diverse environments.

Main Methods:

• Analysis of extensive datasets on species occurrences and functional traits from coral reef fishes, alpine plants, and tropical trees.
• Assessment of local abundance and regional occupancy to identify rare species.
• Evaluation of functional trait combinations to determine species supporting unique or vulnerable functions.

Main Results:

• Distinct trait combinations supporting ecosystem functions are predominantly found in rare species.
• Species with low functional redundancy, supporting vulnerable functions, are rarer than expected by chance.
• A significant proportion of species supporting vulnerable functions were locally and regionally rare, with some having very low abundance.

Conclusions:

• Rare species are critical for maintaining the breadth of ecosystem functions, even in species-rich ecosystems.
• Conservation of rare species is essential for ecosystem resilience and adaptation to future environmental changes.
• Understanding the role of rarity and functional vulnerability is key for effective ecosystem management and conservation strategies.