Soils are some of the most complex ecosystems on Earth, and fungi must trade to survive. Animals rely on a central nervous system to make trade decisions, but fungal networks must evaluate trade environments without a brain. First, they must forage for nutrients in the soil (like phosphorus and nitrogen). Second, they must exchange these nutrients for carbon compounds (like sugars and fats). To do this, mycorrhizal fungi have evolved sophisticated trading strategies, and can discriminate between plant partners, exchanging more resources to plants that provide them with more carbon. Fungi can capitalize on value differences across complex trade networks by moving resources to where they gain a better price from plant ‘buyers’. In one study, when faced with an unequal supply of nutrients across their networks, mycorrhizal fungi moved phosphorus to areas of scarcity, where it was in higher demand and therefore fetched a higher ‘price’. By doing so, the fungus was able to receive larger quantities of carbon in return. Fungi can even hoard resources until they retain a higher ‘price’. Researchers are using new tools to tag nutrients inside fungal networks and track fungal trade decisions.
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