I am looking for suggestions for analyses that can compare of different taxa in terms of the relative difference in composition among sites.
I have 4 parallel datasets of species abundance data from 4 different taxa sampled in the same sites (n=12).
Each site was sampled between 4 - 10 times. Usually (not always) sampling was done at the same time for all taxa within a site, but not all sites were sampled at the same time so the data are unbalanced.
I can create balanced subsets if needed but this would severely truncate the data.
I've heard of co-correspondence analysis, co-inertia anlaysis, and possibly multiple-factor analysis as potential candidates for doing this type of comparison but I'm not sure about the differences or which is most appropriate.
Are there pros and cons/restrictions/assumptions for each of these?
Is there an alternative method that I have mentioned that would be better?
Also what do these analyses allow me to test exactly - is their intention is to be able say for example that taxa A and B had high correlation in terms of variation in composition across sites, while taxa C showed low correlation with any other taxa ...etc ?
Thanks
Tania
See SPSS statistics software. Maybe you can find something similar to your problem.
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Any statistical software like SPSS, Statistica can help for your objective.
Before that, list down pointwise, what are your requirements? For example,
Determine the presence/absence of difference between different species diversity, population between sites or times of sampling in the same site, etc.
Determine the presence/absence of composition of species between sites, species types, time of sampling, etc.
Determine the "factors" that contribute to the difference,
Etc.,
Then, only then you can choose between the statistical tools.
On hearing, it would be possible to suggest the statistical tool for each purpose.
Best wishes for successful tests.
Dear Tania,
There is a lot of possibility for multivariate analysis. With R and the library ade4 all these analyzes are possible. The University of Lyon puts on line many tutorials
https://pbil.univ-lyon1.fr/ade4/article/jss/jss.pdf
http://pbil.univ-lyon1.fr/ade4/home.php?lang=eng
It exits a forum ade or you can ask this kind of question:
http://listes.univ-lyon1.fr/wws/info/adelist
The choice of the analysis will take on the questions you ask yourself: to put in evience the differences between the sites whatever the dates or on the contrary to highlight dates that deviates from an average ....
I think of an analysis within - Between :
https://pbil.univ-lyon1.fr/R/pdf/course4.pdf
or K table :
https://pbil.univ-lyon1.fr/ade4/article/rnews2/rnews2.pdf
You will need to see the dataset and the questions you are asking yourself
Thank you for all your responses.
The question I would like to ask is
1) do the spatial patterns of diversity differ among taxa? For example one taxa may show high clustering of sites based on habitat type, while another will show similar composition across all sites.
2) do spatial trends differ over time- for example, one taxa may show stable composition in all habitats over time while another taxa may show convergence of composition between habitats, and a third taxa may show high variability over time for one particular habitat...
The intention is to demonstrate the different taxa have different spatial and temporal distributions and therefore can or cannot be used as surrogates for each other based on composition.
3) Characterise the similarity (betadiversity) between and within habitat types, based on all taxa.
I can of course compare univariate measures of diversity in each site using anova but I would like to compare the taxa based on their composition.
Thanks for further suggestions to address these specific research questions..
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