PERSPECTIVE article
Front. Microbiomes
Sec. Environmental Microbiomes
This article is part of the Research TopicWomen in Environmental Microbiomes Vol. II: 2024View all articles
Multilevel selection theory informs context-dependent mycorrhizal functioning
Provisionally accepted
- 1Department of Biology, University of Miami, Coral Gables, United States
- 2Biogeochemical Sciences Branch, US Army Engineer Research and Development Center Cold Regions Research and Engineering Laboratory, Hanover, United States
- 3Department of Biological Sciences & School of Earth and Sustainability, Northern Arizona University, Flagstaff, United States
- 4Department of Environmental Studies, Dartmouth College, Hanover, United States
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Arbuscular mycorrhizal (AM) fungi form widespread, ancient, and critically important symbioses with plants, but their functioning and beneficial effects are highly context-dependent. This variability stems from eco-evolutionary dynamics operating across multiple levels of biological organization (e.g., genes to holobionts), making generalizable predictions about mycorrhizal outcomes challenging. Multilevel selection theory (MLST), which posits that selection acts simultaneously on multiple levels of biological organization including in opposite directions, can serve as a powerful framework for interpreting this variability in mycorrhizal functional phenotypes. Here, we outline the key principles of MLST and explore how its application to AM fungal symbioses can improve our understanding of this ubiquitous symbiosis. We highlight how four levels of biological organization important to AM symbioses – genes, nuclei, spores, and holobionts – can serve as one or more units of selection under a tripartite framework for the units of selection. We then examine how ecological contexts, such as stress, spatial structure, and community composition, can modulate the balance of selective forces across levels, ultimately shaping the degree of cooperation among symbiotic partners. We conclude by proposing future research directions using MLST to generate deeper insights into the complexity and adaptability of this globally important symbiosis.
Keywords: Multilevel selection theory, arbuscular mycorrhizal fungi, holobiont, cooperation, context-dependency
Received: 30 Jul 2025; Accepted: 02 Dec 2025.
Copyright: © 2025 Katula, Johnson, Chaudhary and Afkhami. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Anne M. Katula
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