Structure and robustness of “pollinators-plants-herbivores” network in the alpine meadow of the Northwestern Sichuan Province

Abstract

<p indent="0mm">Pollination and herbivory are the two most common plant-animal interactions in terrestrial ecosystems. Such mutualistic and antagonistic interactions intertwine in an integrated network, thereby driving the population dynamics of interacting species and resulting in community stability. However, “plant-pollinators” and “plant-herbivores” networks have frequently been studied only in isolation. Therefore, it remains unclear how they are coupled in an integrated network. Hence, we investigated an integrated network composed of pollinators and pre-dispersal seed predators. We also investigated their interacting plant species in the alpine meadow of the Northwestern Sichuan Province. The results showed that both mutualistic and antagonistic interaction networks exhibited a significant nestedness structure, i.e., specialist animals interacting with generalist plants and <italic>vice versa</italic>. Nevertheless, modularity was also detected in “plant-seed predator” and quantitative “plant-pollinators” networks in which the species interacted more strongly within than between modules. Plant species that interact with more pollinators suffer from more herbivores and more specialized herbivores. Additionally, the observed pollinators and herbivore communities were significantly more robust when plants were randomly lost in a specialist to generalist order. However, these communities were less robust when plants were lost from the generalist to the specialist orders when compared to the null networks where the links were randomly assigned among plants and insects. Furthermore, the herbivore community was robust against the loss of pollinators in such an integrated network. In conclusion, our results propose that the coupling of mutualistic and antagonistic networks promotes the robustness of a whole community.