Fig 1.
Abiotic and biotic effects on plant-AMF mutualistic outcomes when inoculated with fungi from an elevation gradient.
A) Abiotic effects: AMF community composition in Joshua tree roots changes along an elevation gradient. Elevation gradient in the figure corresponds to a changing climate gradient with warmer temperatures at the lowest elevations and the coolest temperatures at high elevations. Changes in fungal communities are represented by the assorted changing black shapes. B) Biotic effects: Variation in the AMF community correspond to different symbiotic outcomes for Joshua trees. Outcomes can range from positive to negative with the arrow demonstrating fungal parasitism (+, -) of the tree, commensalism (+, 0) with the fungus benefitting but not damaging the tree, or mutualism (+, +) with both the tree and the fungi benefitting.
Fig 2.
Percent mycorrhizal colonization of Joshua tree roots measured as a function of elevation.
Solid line represents the fitted values from a generalized additive model that estimates the form of a relationship between the thirty-three root samples and elevation. Points show values for each of the three samples taken at a site. GAM fit indicates a greater degree of colonization for roots at lower elevations than higher elevations. Dotted lines represent 95% confidence intervals.
Fig 3.
Bootstrap consensus tree and heatmap of the relative abundances of each AMF virtual taxon (VT) across the elevation gradient in Joshua Tree National Park, CA, USA.
The tree was built using the Maximum Composite Likelihood method [55] and evolutionary analysis conducted in MEGA7. Node numbers represent Bootstrap values with only those values above 50 displayed. Tips represent AMF species name and VT as they are listed in the MaarjAM database. For the heatmap, rows represent the presence of AMF and the darkness of square indicates the read abundance expressed on a scale from 1–10 of each VT shown on the tree, at each elevation sampled.
Fig 4.
Relative abundances of genera of AMF taxa colonizing Joshua tree roots harvested across an elevation gradient in Joshua Tree National Park.
Abundance is estimated as the proportion of assigned sequence reads within each site.
Fig 5.
Biplot of first two components (PC1 and PC2) of a principal component analysis of eleven sites, based on the relative abundance of major fungal taxa.
Each point is labeled with the elevation in meters of one of the eleven sample sites. The arrows represent the loadings for each AMF taxon across all sites. The 8 taxa with the strongest loadings are labeled using the first 4 letters in the genus name, and the last three numbers in the virtual taxa ID, for example: Scutellospora sp.:VTX00052 = Scut052.
Fig 6.
Responses of Joshua tree seedlings to treatment with different fungal communities.
(A-D) Joshua tree seedlings inoculated with fungal communities from one of the 11 elevation sites, or as no-AMF control, and were destructively harvested at 1, 3, 6, and 9 months (averaged in triplicate). (E) Mycorrhizal growth response for Joshua tree seedlings (given as log mycorrhizal response ratio) at various monthly intervals following inoculation with whole fungal community inoculum from one of the eleven sites from across an elevation gradient. Log mycorrhizal response ratio is calculated as log (biomass treatment/biomass control). Colors correspond to AMF communities taken from field sites that range from warm to cool along an elevation gradient, or black for control, and points corresponding to nutrient analysis are jittered horizontally around value with error bars showing 1 SD. Line styles correspond to low-(dot-dash line), mid-(dotted line), and high-(dashed line) elevation fungal groups, or solid for the control.