Fungi prepare the soil for plant invasions

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How do invasive plants muscle out native species? Is it all down to their own efforts, or do they get help? Dasheng Sun and colleagues examined partnerships between Asteraceae plants and arbuscular mycorrhizal fungi. In a paper, in a forthcoming issue of New Phytologist, they report that these interactions between invader and fungi help some plants outcompete their native near-relatives.

Sun and colleagues found that arbuscular mycorrhizal fungi increased the competitiveness of invasive plants by increasing shoot nitrogen, phosphorus, and root myristic acid concentrations. They also found increased expression of some fatty acid transporter genes. In contrast, native plants colonised by the fungi had reduced expression of the same genes.

Partnerships with fungi are critical for many plants, as they can act like extra roots, increasing the volume of soil a plant can exploit massively. In return for passing along nutrients like nitrogen and phosphorus, they receive carbon from the host plant, in this case by the myristic acids. By activating a better partnership with these fungi, the invasive plants win the competition for nutrients below ground.

A pair of hands grabbing soil. It turns out finding photos of near invisible fungi in soil is surprisingly difficult. — It’s the fungi you can’t see in the soil that grab the nutrients as well as the roots that you can see. Image: Canva.

It’s a competition worth winning. Sun and colleagues refer to research that shows fungi can provide a plant with up to 80% of its phosphorus and 25% of its nitrogen. It’s also a very common way to get these nutrients. Studies show that four-fifths of vascular plants form partnerships with fungi.

The team conducted two experiments to test the role of the fungi. First, they grew the plants in bulk soils with all microbes, to mimic real-world conditions. In the second, they focused on the role of the arbuscular mycorrhizal fungi by sterilising the soil and then inoculating the soil with the fungi to remove the effects of interference from other microbes.

As the invaders and the natives are different species, it can be challenging to pull apart the reasons for their success or failure. By choosing relatively closely related plants, Sun and colleagues reduced some of the effects due to the plants themselves, allowing the benefits of the fungal partnership to be seen.

READ THE ARTICLE

Sun, D., Yang, Xueping, Wang, Y., Fan, Y., Ding, P., Song, X., Yuan, X. and Yang, Xuefang (2022) “Stronger mutualistic interactions with arbuscular mycorrhizal fungi help Asteraceae invaders outcompete the phylogenetically related natives,” New Phytologist. https://doi.org/10.1111/nph.18435