Impact of tillage intensity and an invasive grass on plant-pollinator networks in riparian agroecosystems

Insects are a main component of a stable ecosystem and influence crop production. Pollinators, in particular, by regulating pollination between flowers, shape and secure plant communities around crop fields. They are also essential for food provisioning by sustaining the pollination of crops. Studies in recent decades have been covering the mixture of effects various factors have on pollinators. However, there is still a gap in understanding how different taxa in pollinator guilds respond to these pressures and how is network structure affected by it. Therefore, here we tried to further uncover the complex relationship between habitat suitability and pollinator biodiversity in an agro-riparian matrix. Using bipartite network analysis and geographical information systems (GIS) in four sites with different land cover configuration, we assessed faunal and floral diversity, land cover differences and network metrics. Hymenoptera were responsible for most of the visits, while also exhibiting higher levels of richness across sites. Lepidoptera on the other hand, were the order less represented. Overall, tillage intensity and Arundo donax were determinant in differences in the number of visits for both orders, with Diptera and Coleoptera being less affected. However, results regarding visitation rates reported tillage’s higher explanatory power, in comparison with A. donax. Intensive sites showed significantly higher levels of nestedness and lower specialization and diversity across taxa. The results suggest that intensive agriculture and exotic species infestation can impact pollinator taxa differently, thus influencing network structure. By scoping network metrics, we can better determine what species are more affected by agricultural expansion, assess ecosystem resilience and consequently, determine appropriate conservation measures to maintain stable plant-pollinator networks.