Diversity and beyond: plant functional identity determines herbivore performance.

Area of Science:

• Ecology
• Biodiversity research
• Insect-plant interactions

Background:

• Biodiversity change studies often focus on community-level effects, with fewer examining specific biotic interactions.
• Understanding how plant diversity influences individual herbivore population ecology is crucial for plant-insect-herbivore relationship research.

Purpose of the Study:

• To investigate the relationship between plant species diversity and the performance/fitness of the generalist herbivore, Chorthippus parallelus.
• To determine the impact of plant species richness and functional group composition on grasshopper survival and reproduction.

Main Methods:

• Experimental grassland communities (1-60 plant species) were established in the Jena biodiversity experiment.
• 1620 fourth-instar Chorthippus parallelus nymphs were introduced into cages on these communities.
• Grasshopper survival, oothecae production, and hatchling numbers were monitored.

Main Results:

• Grasshopper survival was not affected by plant species richness or functional group richness but increased with the presence of grasses.
• Plant functional group composition significantly influenced fitness measures; grass presence enhanced oothecae production and hatchling numbers.
• A 'rescue effect' was observed where grasshopper performance improved with multiple plant functional groups in the absence of grasses.

Conclusions:

• Plant functional group identity, rather than species richness, is a key driver of Chorthippus parallelus fitness.
• The presence of grasses and diverse plant functional groups can positively influence grasshopper survival and reproductive success.
• These findings highlight the importance of plant community composition in mediating herbivore population dynamics.