XLSTAT: Permutational MANOVA or Adonis in Excel

 

Background

Adonis is a technique used in ecology to explain communities with environmental variables. Its goal is similar to Multivariate Analysis of Variance (MANOVA).

The adonis function developed in XLSTAT-R calls the adonis function from the vegan package in R (Martin Henry H. Stevens and Jari Oksanen).

 

Dataset for Example

Dataset: Extracted from Vegetation and Environment in Dutch Dune Meadows (Jongman et al., 1987), available in the vegan R package.

• Observations: 20 sites

• Variables:

  • Plant abundances: 30 species (columns 1–30)

  • Environmental variables:

    • A1: Thickness of the A1 soil horizon (numeric)

    • Management: Categorical with 4 levels — BF, HF, NM, SF

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Objective:
To analyze the effect of:

• A1 soil thickness

• Management type

• Their interaction

on the composition of plant communities (species abundances).

You can approach this with multivariate analysis, e.g. RDA (Redundancy Analysis) or PERMANOVA, using species data as response and A1, management, and their interaction as predictors.

 

Setting Up

• Open XLSTAT.

• Click on the XLSTAT-R / vegan menu and select the Permutational MANOVA using Distance Matrices(adonis) feature.

  

• In the General tab of the dialog box:

  • Dependent variables: Select the plant community data (columns 1–30).

  • Quantitative explanatory variable: Select A1.

  • Qualitative explanatory variable: Select Management.

 

In the Options tab:

• Activate the  interactions, set permutations at 999 and select Marginal effects. Marginal effects are equivalent to the type III sum of squares table.

 

• Click on the OK button to launch the computations.

• A dialog box appears allowing you to select the terms you want to include in your model.

• Select all the terms and click OK.

 

Interpreting the Results

The adonis ANOVA table shows that A1 & Management have significant effects on the community at alfa = 0.05. The interaction effect is not significant.