Impacts of global changes on food web structure

The food web sustains its structure mainly by bottom-up and top-down regulations of the species interactions among different trophic levels. However, global changes can alter interspecific relationships and threaten the maintenance of biodiversity. It is still unclear how global change alters the structure of the food webs. In recent years, based on numerous studies on food webs composed of multi-trophic levels at large spatiotemporal scales, researchers have found that global changes alter food web structure mainly through three mechanisms: phenological mismatching, loss of key species and biological invasion. Here we focused on these three mechanisms and reviewed how these mechanisms regulate food web structure change, with further discussions on the driving factors in ecology and evolution. All these three mechanisms can alter the interspecific interactions, resulting in distortion of the regulation of food webs. The major difference among these three mechanisms is how interspecific interactions are changed. Phenological mismatching occurs due to the asynchronous responses in the phenology of different species to global changes, while the loss of key species can change or even entirely destroy some critical feeding/predation relationships, and invasive species often simplify the food web structure by causing strong interspecific competition to exclude species at the same trophic level. Finally, we pointed out that the changes in food web structure actually depend on the adaptation of species to the ongoing global changes and we further provided some insights into future research directions. With aggravated global change impacts, it is necessary to further study the mechanisms underlying how global changes influence food web structure, to reinforce the extant theoretical basis for formulating biodiversity conservation and ecological restoration measures.