Primary consumers (herbivores) continue to undergo substantial changes associated with global environment change (GEC), potentially affecting diversity, structure, and function of biological systems given their importance for these processes. This is especially true for insects – invertebrate primary consumers have substantial ecological and evolutionary impacts on plants, including diversity and biomass – these impacts stand to be transformed depending on how human disturbances on contemporary landscapes affect insect consumers.
As with all primary consumer groups, theoretical models on the regulation of insect herbivores emphasize interactions between resource-based bottom-up processes and predatory top-down influences. These processes are likely to be affected by GEC thru eutrophication and habitat fragmentation causing the loss of apex insect predators, or changes in plant diversity. How these changes affect primary consumers, however, is unclear because of potentially co-occurring or confounded effects.
We propose to examine these issues with a large-scale field experiment, testing co-occurring impacts of environmental changes on primary consumer communities. We focus on a range of measures – spatial distribution, diversity, and total abundance – given that not all should respond similarly. We focus on naturally assembled communities starting from bare ground to eliminate the potential for significant biases due to past ‘legacy effects’ that make it impossible to separate deterministic versus stochastic influences on the structure of primary consumer communities. We work in grasslands, focusing on insect primary consumers on plants. We quantify responses to several treatments – eutrophication, habitat loss, and grassland perturbation by plant removal – at three levels: plants (food source for primary consumers), primary consumers, and predators of primary consumers.
