Table 1. Hypothesis testing framework and consensus approach (see methods) to verify differences in α and β microbial diversity (detailed results in S2 Table).
Location effects | α diversity–ANOVA (ASVs frequencies) | β diversity–PERMANOVA (CLR-CoDa) | β diversity–PERMANOVA (ASVs frequencies) | |||||||
---|---|---|---|---|---|---|---|---|---|---|
ACE | PD | H | IS | CLR ASVs | CLR aggregated genera |
untransformed | 4rt root | – log(X+1) | presence/absence | |
Management Practice: Ma | * | ** | ||||||||
Altitude: Al | ||||||||||
Crop: Cr | * | |||||||||
Ma x Al | * | ** | * | * | * | * | * | * | ||
Al x Cr | ||||||||||
Ma x Cr | ||||||||||
Site: Si (Ma x Al) | *** | *** | *** | *** | *** | *** | ||||
Al x Ma x Cr | ||||||||||
Cr x Si (Ma x Al) | ** | *** | *** | *** | *** | *** | *** | *** | ||
posthoc test Ma x Al | ||||||||||
high altitude | conv. > agroec. | Conv. > agroec. | Conv. ≠ agroec. | Conv. ≠ agroec. | ||||||
Low altitude | conv. = agroec. | Conv. = agroec. | Conv. = agroec. | Conv. = agroec. | ||||||
Dispersion effects (Anna Karenina) | β diversity–PERMDISP (CLR-CoDa) | |||||||||
CLR ASVs | CLR aggregated genera | |||||||||
Management Practice, High | conv. > agroec. | Conv. > agroec. | ||||||||
Management Practice, Low | conv. = agroec. | Conv. = agroec. |
ANOVAs (on ASVs frequencies) and PERMANOVAs (on either ASVs frequencies or centered log-ratio transformed, compositional data, CLR-CoDa) were used to test univariate and multivariate location effects of management practice (Ma: conventional vs agroecological), altitude (Al: high altitude vs low altitude), crop (Cr: watermelon vs cucumber), and site (list and coordinates in S1 File). PERMDISP, based on CLR-CoDa, was used to test dispersion effects on β diversity (Anna Karenina principle) promoted by different management practices either at high or low altitudes. FDR: p value corrected via False Discovery Rate. Tests on α microbial diversity considered Abundance Coverage Estimator (ACE), Faith’s Phylogenetic Diversity (PD), Shannon-Weiner (H) and the Inverse Simpson indexes (IS). The results of the post hoc tests implemented for Ma x Al are indicated.
*: P = <0.05
**: P = <0.001
***: P = <0.0001.