Fire and grazing modulate the structure and resistance of plant–floral visitor networks in a tallgrass prairie
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Significant loss of pollinator taxa and their interactions with flowering plants has resulted in growing reductions to pollination services globally. Ecological network analysis is a useful tool for evaluating factors that alter the interaction structure and resistance of systems to species loss, but is rarely applied across multiple empirical networks sampled within the same study. The non-random arrangement of species interactions within a community, or “network structure” such as nested or modular organization, is predicted to prevent extinction cascades in ecological networks. How ecological gradients such as disturbance regimes shape network structural properties remains poorly understood despite significant efforts to quantify interaction structure in natural systems. Here, we examine changes in the structure of plant–floral visitor networks in a tallgrass prairie using a decadal and landscape-scale experiment that manipulates prescribed burn frequency and ungulate grazing, resulting in different grassland states. Plant and floral visitor communities and accompanying network structure were impacted by grassland fire and grazing regimes. The presence of grazers increased flowering plant species richness, network floral visitor species richness, and decreased network nestedness. Fire frequency affected flowering plant and floral visitor community composition; community composition impacted network specialization and modularity. Grassland state resulting from fire-grazing interactions has important implications for the resistance of flowering plant and floral visitor communities to species loss.
KeywordsPollinators Interactions Ecological networks Community ecology Disturbance
We thank Jan Metlevski for identification of Lepidoptera and Chyna Pei for identification of Apoidea. We are grateful to Savannah Putnam, Kelsey Girvin and Vera Smirnova for their assistance with fieldwork. Keith Gido, John Blair and Gregory Zolnerowich provided insightful comments that greatly improved the quality of this manuscript. Grants from National Science Foundation (NSF) Division of Experimental Biology, NSF Research Experience for Undergraduates, NSF Long Term Ecological Research and Konza Prairie Biological Station supported this research.
Author contribution statement
EARW and AJ formulated the idea. EARW conducted the fieldwork, insect sorting, analyzed data and drafted the manuscript. AJ provided conceptual advice and edited the manuscript.
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