Mycorrhizal response is the most common metric for characterizing how much benefit a plant derives from mycorrhizal symbiosis. Traditionally, ecologists have used these metrics to generalize benefit from mycorrhizal symbiosis in plant species, ignoring the potential for plant intraspecific trait variation to alter the outcome of the mutualism. In order for mean trait values to be useful as a functional trait to describe a species, as has been attempted for mycorrhizal response traits, interspecific variation must be much larger than intraspecific variation. While the variation among species has been extensively studied with respect to mycorrhizal response traits, variation within species has rarely been examined. We conducted a systematic review and analyzed how much variation for mycorrhizal growth and nutrient response typically exists within a plant species. We assessed 26 publications that included 56 individual studies testing mycorrhizal response in at least five genotypes of a plant species, and we found that intraspecific trait variation for mycorrhizal response was generally very large and highly variable depending on study design. The difference between the highest and lowest growth response in a study ranged from 10% to 350% across studies, and 37 of the studies included species for which both positive and negative growth responses to mycorrhizae were observed across different genotypes. Phosphorus concentration and content were measured in 15 studies and variation was similar to variation in growth responses. We also found that plant genotype was just as important for predicting mycorrhizal response as the effects of fungal inoculant identity. Our analysis highlights not only the potential importance of intraspecific trait variation for mycorrhizal response but also the lack of research that has been done on the scale of this variation in plant species. Including intraspecific variation in research on the interactions between plants and their symbionts can increase our understanding of plant coexistence and ecological stability.

See full text of the article for a description of data collection and analysis. A systematic review of published literature identified papers that studied mycorrhizal responses in more than five genotypes of the same species. The presented data were extracted from these sources and used to document variation in mycorrhizal growth response and mycorrhizal phosphorus response within plant species. These data were also used in a meta-analysis of correlations between growth and phosphorus response, as well as to determine the relative importance of plant genotype when compared to mycorrhizal isolate/species and phosphorus treatments.

Data is presented in two forms: raw data (plant biomass, phosphorus concentration, and phosphorus content) from each study in individual CSV files, and processed data (mycorrhizal growth response, mycorrhizal phosphorus response) that includes all studies used in a given analysis. The Web of Science search results from the keywords provided in the full text of the associated article are also provided.