Interaction networks between aphids and their fungal pathogens: Insight into host-pathogen specificity and crop systems dependency

The networks formed by the interactions between aphids and their pathogenic fungi are of high importance for understanding population interactions and ecosystem services, and for an increased use of fungi in biological control. Yet, these networks are poorly known, and particularly the impact of crop systems in shaping these associations are seldom considered. We established a hypothetical interaction network between aphids and their fungal pathogens based on published data to (1) investigate the fungus-host specificity and their dependency on their habitat, and (2) assess the dissemination of aphid mycoses among nine major cropping systems. Of the more than 3000 unique connections between these host and pathogen taxa, we identified pathogen specificity and assessed, which role the most commonly connected aphid species can play in the dynamics of fungal infection within and between crop systems. Fungi within the Entomophthoraceae had the highest number of connections to aphids. Pandora neoaphidis and Entomophthora planchoniana had the most connections to aphid species, suggesting that they are likely to play a key role in the establishment and dispersal of infections in aphid populations worldwide. From the aphids’ side, Myzus persicae had the highest degree of most connections in
the network followed by the cereal aphids Rhopalosiphum padi and Sitobion avenae, suggesting that these species are highly prone to fungal infections and therefore important players of the fungal dissemination between crop systems. The highest number of aphid species and fungal connections was present in orchards, followed by vegetable and cereal crops. Insights into the correlations between the aphid-fungal pathogen interaction networks and the impact of crops on these associations provide the basis for prediction of the infection pathways in real-life ecological systems.