Elevational patterns of taxonomic groups
All taxonomic orders of ECM and root-associated fungi in the Neotropical sites that correlated significantly with the ordination axes exhibited highest richness in upper montane forests (e.g., Agaricales, Archaeorhizomycetales, Eurotiales, Helotiales, Hysteriales, Russulales, Sebacinales, and Thelephorales). In Borneo, vectors of richness for most taxonomic orders of ECM and root-associated fungi were directed towards the lower montane forest sites, with the exception of Sordariales and Thelephorales with highest richness in lowland forests, and Helotiales in upper montane forests (Fig. 2).
Vectors representing the richness of most taxonomic groups of plant pathogens with significant correlations (e.g., in Botryosphaeriales, Cantharellales, Diaporthales, Hypocreales, Ophiostomatales, Polyporales, Rhizophydiales, and Xylariales) were directed mostly towards lowland forests, whereas putatively pathogenic Helotiales were more rich in lower montane forests (Borneo) or upper montane forests (Panama).
Orders of saprotrophic fungi that were richer in forests at lower elevations included Agaricales, Eurotiales, Geastrales, Hypocreales, Kickxellales, Saccharomycetales, Sporidiobolales, and Sordariales, each with significant Pearson’s correlation values in at least two regions. In contrast, vectors for saprotrophic Chaetothyriales, Helotiales, and Sebacinales indicated higher richness in montane forests. Among wood decomposers, Helotiales consistently showed highest richness in forests at higher elevations, and Agaricales and Xylariales at lower elevations (Fig. 2).
Overall, Archaeorhizomycetes, Leotiomycetes, Saccharomycetes, and Sordariomycetes differed significantly in richness among the elevational forest types in all three regions (Fig. S7). In particular, richness of Leotiomycetes and Sordariomycetes consistently was higher and lower, respectively, in upper montane than in lowland forests. Richness of Archaeorhizomycetes and Saccharomycetes peaked in lower montane forests in Borneo and Panama, but they showed contrasting patterns in Argentina (i.e., their richness increased and decreased with elevation, respectively). The Mortierellomycotina subphylum was always more rich in montane forests than in the lowlands, though the difference was not significant in Argentina. Similarly, significant differences in richness of Agaricomycetes among the elevational forest types were only detected in Borneo and Panama, where contrasting patterns were observed (i.e., higher and lower richness in lowland than in upper montane forests, respectively) (Fig. S7).