Trophic interrelationships drive the biogeography of protistan community in agricultural ecosystems

Protists are essential for nutrient cycling and plant performance in diverse ecosystems. However, the biogeographic patterns and driving forces (i.e. abiotic or biotic factors) of protistan communities remain poorly understood in agricultural ecosystems. Here, the biogeographic patterns of soil protists were assessed in adjacent pairs of maize and rice fields across eastern China. By combining our results with previously published datasets, we presented the first evidence that the α- and β-diversity of protists were highly structured by bacterial diversity in maize soils and fungal diversity in rice soils, respectively. Consistently, network analyses showed higher connectedness of protists to bacteria in maize soils, but higher connectedness of protists to fungi in rice soils. In addition, bacteria were more correlated with protistan consumers in maize soils, whereas fungi were more associated with protistan phototrophs. Protists in rice soils with lower diversity displayed broader environmental breadth and stronger phylogenetic conservatism than those in maize soils. Taken together, our results provides novel insights into the importance of biotic factors (trophic interrelationships) in driving the biogeographic patterns of soil protistan community in distinct agricultural ecosystems.