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Cross Validated

Questions tagged [vegan]

R package for community and vegetation ecology. Includes ordination methods, diversity analysis, etc.

40 questions
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1answer
19 views

odd insignificant results using pairwise.perm.manova

I am trying to complete pairwise comparisons of 9 forest communities. Communities were significant at p < 0.001 using adonis. However, when I use the same bray curtis matrix with the pairwise.perm....
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0answers
12 views

R: Statistically testing NMDS community differences

Situation I am comparing species communities at 6 different sites. Communities at each site were measured repeatedly over 5 years. I used NMDS plots, based on bray-curtis distance matrices using ...
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0answers
17 views

How to determine which species are biggest contributors to overall variation in community?

I have data on the community of microbes from different soil types, however I do not have any environmental variables, only categorical (sites). I have generated PCoAs with distance matrices, however ...
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0answers
22 views

Evaluating ecological community over time with NMDS?

I have sampling data of insect communities per month for 7 months. The sampling occurred in the same location with the same methods once a month. I want to be able to see community changes over time ...
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0answers
41 views

Comparing species correlations between species in two habitats

I have two community data sets (samples as rows, species as columns, populated with abundance). This data comes from two habitats/sites, with differing numbers of samples at each site. What I want ...
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0answers
9 views

Comparing relative distances between separate ordinations

I have four sites: Treatment_1 and Control_1 of experiment 1 (8 plots in total) Treatment_2 & Control_2 of experiment 2 (8 plots in total) I ran an RDA for each experiment separately to compare ...
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0answers
66 views

Variation partition analysis: morphology-climate correlation, controlling for geography

I'm working with three datasets with informations about individuals: morphological data, climatic data of the individual sampling site and geographical data. My objective is to assess whether ...
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0answers
67 views

Remove highly correlated variables before regression - partial or pairwise correlation?

I am using vegan's bioenv() function to find the best (sub)set of variables in one distance matrix (env parameters) that explain the structure of another distance matrix (species abundance). Several ...
0
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1answer
124 views

RDA and CCA output- unconstrained inertia 0.00 rank 0

I get an ouput for RDA and for CCA that says that my unconstrained inertia is 0, rank 0. I thought that would be a good thing in the meaning that all the variance in the data is explained by my (...
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0answers
50 views

How to choose an ordination method for your dataset?

I'm looking for advice on how to choose the correct/best ordination method for my data. My data set: Plant species abundance by plot. Approx 150 plots w/ 40 different plant species. The plots are ...
1
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0answers
92 views

metaMDS: Choosing a solution (lower stress vs higher # of dimensions) [closed]

I'm new to ordination and the Vegan package in general. Right now I'm using the vegan NMDS function (metaMDS) to look at a data set that has species cover by plot. The data set has a high percentage ...
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0answers
38 views

R, vegan: Is it possible to get effect direction from adonis results?

I used the vegan package and the adonis function to test the impact of a variable on communities. As far as I understand, the output tells me that there is an effect, but it does not tell me if there ...
0
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0answers
23 views

How to view the predicted unimodal response of a Canonical Correspondence Analysis?

I'm trying to understand the predicted patterns of a Canonical Correspondence Analysis (CCA). I understand one of this method's strengths in understanding ecological patterns lies in its assumption of ...
1
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0answers
87 views

What do standard deviation ellipses mean in an ordination plot?

When kind = 'sd, ordiellipse() draws a single ellipse representing the "standard deviation' around each cluster in an ordination ...
1
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0answers
197 views

Can you use bray-curtis distances to evaluate standardized abundances in an NMDS?

So I'm trying to run an NMDS (using the vegan package in R) for a species X site matrix. Unfortunately the abundances of species are not inherently equal (If you can use that word) meaning that not ...
1
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0answers
313 views

How to code a model with the adonis function in R (permanova) for a paired/matched design (epidemiology study)

We have a database of 100 children that are grouped in 50 paired/matched groups (of 2 children) based on co-variables such as sex, c-section, and antibiotic treatments. We obtained the gut microbial ...
2
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0answers
472 views

R vegan: RDA vs CCA, which test to answer my research question and which results to report?

(if my question should be cut up into sub-questions please let me know, since all those questions are related I decided to ask them here together as one long question) Main question As part of my ...
2
votes
1answer
465 views

Is Hellinger transformation suitable to access species abundance - environmental variable relationships?

While working with a multivariate dataset, I noticed that Hellinger transformation reveals relationships with the dataset I did not see otherwise. The fact that a transformation affects species ...
2
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0answers
143 views

Can I use parametric and non-parametric tests in the same publication?

I have a rather difficult dataset. One measurement is non-normal and zero-inflated and could not be transformed to normality. Thus, a glm was used. Another set of ...
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0answers
24 views

Model matrix, contrast matrix, transferring tutorial to real data

I have been following this tutorial to perform simple main effects on a multivariate data set that shows a significant interaction between two factors. I can't find any other tutorial that does this ...
1
vote
1answer
110 views

Are NMDS Axis the same calculated for one or more dimensions?

I used NMDS axes of an ecological community as proxys for the community similarity in the different samples. I would like to "quantify" the importance of the different NMDS axis according to the ...
0
votes
1answer
707 views

Stress values of an nMDS analysis and p-values of ordisurf()

I have run a nMDS analysis in vegan and I have a few questions on the stress values of the analysis as well as the p-values associated with utilizing the ordisurf() function (also in vegan). First of ...
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0answers
98 views

Test for heteroscedasticity of continuous variables in R similar to betadisper()?

Before using adonis() with factors as explanatory variables in R, it is important to check for group dispersion (betadisper()) so that you know whether your significant p-value from adonis is real, i....
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1answer
348 views

Appropriate PERMANOVA (adonis) call for Subject Identity? (Terms drop in output)

I am working with a dataset of microbial species abundances at time points (baseline, 8h, 24h, 48h, 72h, 96h, 120h) for 23 subjects and have weighted unifrac, unweighted unifrac, and Bray-curtis ...
1
vote
1answer
357 views

What is the reason behind the name “adonis” (for permutational MANOVA)?

Does any one know why Permutational Multivariate Analysis of Variance Using Distance Matrices (PERMANOVA) is also called adonis? See https://www.r-bloggers.com/adonis-permanova-assumptions or http://...
4
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1answer
115 views

How to perform CCA with block design in R

Following example and data are completely fabricated: Suppose I am studying grooming behaviour in apes. I have four cages, 8 apes in each (4 females + males). For 24 hours I did an observations with ...
2
votes
1answer
1k views

Betadisper is significant, can I still do ADONIS and ANOSIM?

I'm a grad student in microbial ecology and I'm comparing some bacterial communities in experimental man made ponds. I've run the PCoA, NMDS, and CCA to see how various variables effect or influence ...
3
votes
1answer
2k views

adonis in vegan: order of variables — non nested with one degree of freedom for each

I am trying to understand why the order of variables seems to effect p values for both of those variables for the adonis() (Permutational Multivariate Analysis of ...
3
votes
1answer
341 views

Can MDS coordinates be used as variables in further analyses?

I have calculated an NMDS from vegetation community data taken from two habitat types using the metaMDS() function in vegan. My ...
0
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1answer
76 views

Should functional groups' abundances be transformed before using RDA?

I want to run Redundancy Analysis (RDA) with the abundance of different functional groups of plants (7 groups in total: shrubs, coniferous, forbs, etc.) as my response variables. I know that, for ...
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0answers
172 views

Should PERMANOVA be used to select factors for Canonical Correspondence Analysis?

I am interested in investigating the relationship between species composition and several environmental factors. My question is whether it is appropriate to use PERMANOVA to select a 'best' ...
1
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0answers
143 views

Specification of permutation design in RDA

I am using RDA to study plant communities in various land uses (variable LU with values M, U, etc.). For each land use, I sample 3 to 5 fields (M1, M2, U1, U2, etc). I make 5 measurements for both ...
1
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1answer
177 views

Calculation of the Shannon Index plotwise or over the entire population

Imagine I inventarized a forest with 28 plots. Do I calculate the Shannon-Index for each plot and take the average, or should I calculate the Shannon-Index over the whole population? I use R and the ...
1
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0answers
158 views

Residuals of symmetric Procrustes analyses are not symmetric

I am trying to replicate the analysis I saw in a paper. One of the step is to describe the relationships between two data tables. I use the procrustes() function ...
0
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0answers
64 views

How to apply standardization to train and test dataset in linear regression

Using decostand{Vegan} to standardize a X variable in linear regression: Approach 1: Should I standardize entire dataset at once? Approach 2: Should I standardize train and test dataset individually? ...
3
votes
1answer
149 views

Displaying large number of text labels on a scatter plot

Having too many species in the data, makes the species labels overlap in a plot of a canonical correspondence analysis. This makes it difficult to interpret. Is there a reasonable possible solution? ...
0
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2answers
82 views

Can I take an average of the values I got from Shannon-Weaver index?

Can I take an average of the values I got from Shannon-Weaver index ? OR Is it wrong to take an average of some values that we get after applying natural logarithm (ln) in an equation, like Shannon-...
0
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1answer
291 views

Variation partitioning in vegan. Do variables need to be centered?

I would like to carry out variation partitioning to see how landscape variables and local variables contribute to variation in species richness. Do I need to centre my data prior to analysis? ...
2
votes
1answer
421 views

CCA species coordinates relative to ordination surface

I want to display species coordinates relative to an environmental variable using ordination surface (ordisurf in vegan package)...
4
votes
1answer
361 views

Standard error for Shannon's index in R

I am interested in examining how the species diversity of bird communities change following timber harvest and have used Vegan in R to run my analyses. Below is a sample of my count data. Plot names ...