Experimental reduction of plant abundance changes interaction frequency of a tri-trophic micro-food web: contrasting responses of generalists and specialists

1. Species abundance is vulnerable to climate change and anthropogenic impact. Although numerous studies have examined the food web response to species loss, their response (e.g. in network topology and interaction frequency) to changes in species abundance has received little attention. 2. We experimentally reduced the abundance (by ca. 60%) of one host plant species (Saussurea nigrescens) in a tri-trophic micro-food web consisting of two common Asteraceae species (S. nigrescens and Anaphalis flavescens), their pre-dispersal seed predators (tephritid flies), and the parasitoid wasps that feed on these seed predators. 3. The neutral process hypothesis posits that network topology and interaction frequency are determined by the relative abundances of the participating species. Accordingly, we hypothesized that interaction frequency (indicated by the rate of flies infesting plants and of parasitoid wasps parasitizing flies) would decrease with decreasing abundance of host plant abundance....