Figure 2.

The flow of matter and energy (yellow arrows) and genetic information (white arrows) through mycorrhizae differs in natural (left) and high-input agricultural (right) ecosystems. Abundance and diversity of arbuscular mycorrhizal (AM) fungi tend to be greater in natural compared to high-input agricultural ecosystems because plants allocate more photosynthate to mycorrhizae when they are nutrient and/or water limited. Communities of soil organisms are generally more diverse in natural ecosystems. Intact networks of AM fungal hyphae and complex foodwebs help conserve nutrients in natural ecosystems, and tillage and fallow periods reduce these networks in agroecosystems so that more nutrients are lost through leaching (yellow arrows). Evolutionary feedback occurs in natural ecosystems because genotypes of plants and AM fungi are selected through reciprocal adaptation to each other and to the environment. This evolutionary feedback is not possible if farmers select plant genotypes without consideration of the indigenous AM fungi and associated microbiome. Illustration by Kara Skye Gibson.