Misdiagnosis of mycorrhizas and inappropriate recycling of data can lead to false conclusions

Abstract

We draw attention to a worrying trend for the uncritical use of 'recycled' mycorrhizal data to compile host species lists that include obvious errors or undertake risky analyses that correlate mycorrhizal colonisation levels with environmental or physiological factors despite inherent limitations in datasets. We are not suggesting that all meta-studies are wrong, only that more care should be taken to resolve what can safely be done with recycled mycorrhizal data in the future. We also recommend that mycorrhizal species lists should be checked against standard references since the majority of EM hosts and NM plant belong to families that are well resolved. However, additional research is required in cases where plant families have multiple root types within genera or occur in habitats where mycorrhizal associations are often suppressed (see Brundrett & Tedersoo, 2018). We hope that the mycorrhizal science community will work together more closely in the future to develop and enforce standards for mycorrhizal diagnosis and to share carefully corrected datasets for realistic meta-studies.

Dual‐mycorrhizal plants: their ecology and relevance

“…There is no one strict definition of what constitutes a dualmycorrhizal plant, in part because of a lack of clear definitions of Identify, clear and stain roots appropriately (Brundrett, 2009;Brundrett & Tedersoo, (2019 what constitutes an AM or EM plant. There is current debate over whether functional or morphological traits are more diagnostic (Brundrett & Tedersoo, 2019;Bueno et al, 2019).…”

“…There is no one strict definition of what constitutes a dualmycorrhizal plant, in part because of a lack of clear definitions of Identify, clear and stain roots appropriately (Brundrett, 2009;Brundrett & Tedersoo, (2019 what constitutes an AM or EM plant. There is current debate over whether functional or morphological traits are more diagnostic (Brundrett & Tedersoo, 2019;Bueno et al, 2019). Mycorrhizal symbiosis has traditionally been defined as mostly involving the mutualistic transfer of carbon (C) from plant to fungus and mineral nutrients from fungus to plant, yet some associations have neutral to negative effects on plant growth in spite of nutrient exchange, especially in higher fertility soil (Smith et al, 2003;Jones & Smith, 2004;Hoeksema et al, 2010).…”

“…seedling, sapling, to mature trees) in the case of tree species. This differs from Brundrett & Tedersoo (2019) in not requiring dual plants to have both EM and AM structures in mature plant roots, which we believe is justified given that seedling establishment and early growth is a critical plant life history stage. As others pointed out, hyphal coils from the Paris colonization type can effectively function like arbuscules (Bueno et al, 2019).…”

Root trait plasticity and plant nutrient acquisition in phosphorus limited soil

“…The extraradical mycelia of AMF may also enter the very fine soil pores, thereby increasing the nutrient uptake (Khalvati et al, 2005). Here, we emphasize the rationale to consider root colonization with AMF as a 'trait' because approximately 18% of angiosperm species (e.g., members of Brassicaceae, Chenopodiaceae, Cyperaceae, Zygophyllaeae families) lack any symbiotic associations with fungi and about 30% of angiosperm species establish other (than AMF) types of mycorrhizal associations (Brundrett, 2002;Brundrett and Tedersoo, 2019). Given that a fungus is considered as mycorrhizal only after its successful interaction with roots to form a specific type of symbiotic association, the consideration of root colonization by mycorrhizal fungi as a trait is highly feasible.…”

Fungal functional ecology: bringing a trait‐based approach to plant‐associated fungi

“…Trait-based approaches have provided important insights for other taxa, such as plants (Kattge et al, 2011;Maitner et al, 2018). Indeed, fungal association type is an explicit trait linked to many plant taxa and used to infer plant nutrient-uptake strategies [but see Brundrett & Tedersoo, 2019 for a discussion of concerns regarding data quality]. We discuss a similar approach for gaining a deeper understanding of fungal ecology and evolution.…”