Effects of predator functional diversity on grassland ecosystem function

Area of Science:

• Ecology
• Ecosystem Science
• Community Ecology

Background:

• Individual predator species significantly influence plant communities and ecosystem functions like production and nutrient cycling.
• Predator hunting mode is a key functional trait determining these impacts.
• The combined effects of predators with different hunting modes on ecosystem function remain largely unknown.

Purpose of the Study:

• To quantify the net effects of two spider species with different hunting modes (sit-and-wait vs. active hunting) on a New England grassland ecosystem.
• To investigate how predator functional diversity, manipulated by varying the dominance ratio of these two species, influences plant composition and ecosystem functioning.

Main Methods:

• An experiment was conducted in a New England grassland.
• A replacement series design was used to manipulate predator functional diversity by altering the dominance ratio of a sit-and-wait and an actively hunting spider species across five treatments.
• Effects on plant diversity, plant litter quality, elemental cycling, and production were quantified.

Main Results:

• Predator functional diversity significantly impacted plant diversity and plant litter quality.
• These effects extended to influence ecosystem processes such as elemental cycling and overall production.
• Many observed ecosystem effects were closely approximated by the weighted average of the individual predator species' effects.

Conclusions:

• Predator functional diversity, driven by distinct hunting modes, has cascading effects throughout grassland ecosystems, influencing both biotic and abiotic components.
• The ecosystem-level impacts of predator functional diversity appear to be largely additive rather than exhibiting strong nonlinearities.
• Understanding predator hunting modes is crucial for predicting their combined influence on ecosystem structure and function.