Landscape heterogeneity affects pollen transport by pollinators in agroecosystems

Abstract

Landscape heterogeneity may afect components of biodiversity, including pollinators and the ecosystem function they perform. Landscape heterogeneity may also afect pollinator movement and pollen and gene fow. We assessed how changes in landscape compositional heterogeneity generated by agricultural activities afect the pollen transport service provided by insect pollinators. In eleven agricultural fragments with diferent landscape heterogeneity, we caught pollinators foraging on fowers and extracted their body pollen loads, discriminating among crop, native, and exotic spontaneous plants. At a local scale, the fragments corresponded to 1-ha plots under agricultural management, or to restored plots without agriculture. The landscape heterogeneity of each fragment was characterized using centered circular areas with diferent diameters (300, 600, and 1000 m). We then calculated the Shannon Diversity Index as a landscape compositional heterogeneity estimator and using the diferent landscape patches identifed (semi-natural pastures, feld crops, woodlands, among others). Through generalized linear mixed models, we found that the amount of pollen transported by individual pollinators was positively related with landscape heterogeneity for all pollen grain categories, but the slope exhibiting a notably sharper incline for crop plant species. In addition, crop pollen load carried by individual pollinator was lower than native and exotic spontaneous pollen, highlighting the importance of these species in agroecosystems. Our fndings indicate that increasing landscape heterogeneity can enhance pollen transport, especially from crops and exotic plants. However, to ensure the sustainability of pollination services and agroecosystem functions, it is crucial to protect native plant species and encourage their growth on crop edges, thereby improving agroecosystem conservation.