Mycorrhizal fungi affect orchid distribution and population dynamics

<jats:title>Summary</jats:title><jats:p>Symbioses are ubiquitous in nature and influence individual plants and populations. Orchids have life history stages that depend fully or partially on fungi for carbon and other essential resources. As a result, orchid populations depend on the distribution of orchid mycorrhizal fungi (<jats:styled-content style="fixed-case">OMF</jats:styled-content>s). We focused on evidence that local‐scale distribution and population dynamics of orchids can be limited by the patchy distribution and abundance of <jats:styled-content style="fixed-case">OMF</jats:styled-content>s, after an update of an earlier review confirmed that orchids are rarely limited by <jats:styled-content style="fixed-case">OMF</jats:styled-content> distribution at geographic scales. Recent evidence points to a relationship between OMF abundance and orchid density and dormancy, which results in apparent density differences. Orchids were more abundant, less likely to enter dormancy, and more likely to re‐emerge when <jats:styled-content style="fixed-case">OMF</jats:styled-content> were abundant. We highlight the need for additional studies on <jats:styled-content style="fixed-case">OMF</jats:styled-content> quantity, more emphasis on tropical species, and development and application of next‐generation sequencing techniques to quantify <jats:styled-content style="fixed-case">OMF</jats:styled-content> abundance in substrates and determine their function in association with orchids. Research is also needed to distinguish between <jats:styled-content style="fixed-case">OMF</jats:styled-content>s and endophytic fungi and to determine the function of nonmycorrhizal endophytes in orchid roots. These studies will be especially important if we are to link orchids and <jats:styled-content style="fixed-case">OMF</jats:styled-content>s in efforts to inform conservation.</jats:p>