Plant consumer impact varies across environmental gradients – first results from the Bug-Network

Invertebrate herbivores and fungal pathogens strongly influence plant diversity and plant community composition,and they additionally mediate key ecosystem functions such as nutrient cycling, carbon sequestration, and decomposition. By regulating plant growth, survival, and competitive interactions, these consumer groups help determine ecosystem structure and functioning. However, despite their recognized ecological significance, empirical knowledge about the individual and combined effects of insects, molluscs, and fungal pathogens on plant communities remains limited. In particular, the extent to which these effects vary across broad environmental gradients, and how multiple consumer groups interact to influence plant performance, is still poorly understood.

 

The aim of the Bug-Network (BugNet) is to address these gaps by experimentally excluding major invertebrate consumer groups and pathogenic fungi in herbaceous-dominated ecosystems worldwide. This coordinated, replicated design enables a direct assessment of the individual and interactive contributions of insects, molluscs, and fungal pathogens to plant growth and damage patterns under contrasting climatic conditions. To quantify these effects, we planted three widely distributed phytometer species—Dactylis glomerata, Taraxacum officinale, and Trifolium pratense—into ten sites participating in the global BugNet consumer-reduction experiment. These sites span a large climatic gradient, with mean temperatures ranging from 5 to 24°C and water balances between –55 and 100 mm. After one growing season, we evaluated consumer impacts by measuring aboveground biomass and estimating herbivore and pathogen damage.

 

Preliminary results show that insect herbivores exert a consistent and detectable influence on plant performance across all study locations. In contrast, the interactive effects among consumer groups are highly context dependent, varying considerably in magnitude and direction along the climatic gradients encompassed by the network. These findings emphasize that consumer impacts cannot be generalized across environments and that climate acts as a key modulator of plant–consumer interactions. Improved understanding of these context-dependent dynamics enhances our capacity to predict shifts in plant communities and trophic interactions under ongoing global environmental change.