Conservation of plant-pollinator networks in agroecosystems: soybean and its field margins in the Argentinian Pampas

DEVOTO MARIANO; LÓPEZ-CARRETERO ANTONIO; MONASTEROLO MARCOS

Uppsala

Congreso; Ecological Networks and Molecular Analysis of Trophic Interactions; 2017

The Pampean region of South America is an extended at area, once dominated by grasslands,that has been dramatically modied by intensive agriculture and livestock grazing. Currently, 60% of the sown area is dominated by a single annual crop, soybean (Glycine max ). Spontaneous vegetation (including many native species) is mostly conned to eld margins, which altogether represent a very small fraction of the landscape. However, plant-pollinator communities in these margins are crucial to sustain the pollination service to various crops (sunower, rapeseed and soybean, among others). Our objectives were twofold: (1) to understand the local and landscape factors that aect the structure of plant-pollinator networks in eld margins, and (2) to explore the factors that aectthe role played by the single dominant mass-owering crop (soybean) in the networks. Along two years we studied 59 soybean plots and constructed the plant-pollinator networks comprised by the crop, the plants in its eld margins and their ower visitors. We included plots with margin widths ranging from 1.5 to 40m, and within surrounding landscapes of varying complexity. We found that eld margin width was far more important than landscape factors (e.g. diversity of land cover types) in structuring plant-pollinator networks. In addition, the complexity of the networks, the evenness of its interactions and its robustness to species loss was positively related to eld margin width, but only up to a width of 8-10m. This has direct management implications, as it sets a maximumwidth beyond which there is no apparent benet to the conservation of plant-pollinator networks. Regarding the role played by soybean in the networks, our results suggest that it is not an attractive oral resource and, thus, its importance in networks' structure is negatively related to the abundance of oral resources in eld margins. In this sense, the behaviour of soybean is somewhat dierent to that of other mass-owering crops such as sunower or rapeseed. All in all, our study is a good example of the usefulness of thenetwork approach to understand and sustainably manage a crucial ecosystem function, such as pollination, in agroecosystems.