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Citation bias and the over-interpretation of results could be leading to a misinterpretation of common mycorrhizal networks — the ‘wood-wide web’— and their role in forests, a Perspective published in Nature Ecology & Evolution argues. The findings, based on literature reviews and citation analysis, suggest that three common claims about the networks of mycorrhizal fungi are insufficiently supported by scientific evidence.
Many plant species, including forest trees, benefit from partnerships with mycorrhizal fungi, which live on plants’ roots and spread in vast networks under the forest floor. That trees can communicate with each other through these fungal networks, for example by sending warning signals to their offspring when damaged, has gained recent traction in the popular media and scientific literature. However, the role of these networks has been debated.
Justine Karst and colleagues analysed evidence for three common claims about common mycorrhizal networks (CMNs) from the media and scientific literature. The authors find that claims that CMNs are widespread in forests and that they transfer resources and increase seedling performance are insufficiently supported because the results from field studies vary, have alternative explanations or are too limited to support generalizations.
They also find that claims that older trees communicate with offspring through CMNs are not supported by any peer-reviewed or published evidence. To examine citations, the authors looked at how 593 papers on CMN structure and 1,083 papers on CMN function referenced findings from 18 early influential papers. They found citations making unsupported statements have risen to 25% for CMN structure and almost 50% for CMN function, and also document a bias toward citing positive effects.
The authors conclude that claims about the positive effects of CMNs are disconnected from the available evidence. They indicate that further research is needed to explore these networks.
IMAGE CREDIT: Matteo Grando/Unsplash