How is UniFrac distance calculated?

UniFrac measures the amount of evolutionary divergence between these two communities by dividing the length of the purple branches by the total branch length of the tree. The example on the left shows two communities which have little evolutionary divergence and therefore a relatively low UniFrac distance.

What is a UniFrac distance?

The unique fraction metric, or UniFrac, measures the phylogenetic distance between sets of taxa in a phylogenetic tree as the fraction of the branch length of the tree that leads to descendants from either one environment or the other, but not both (Fig. 1).

What is UniFrac PCoA?

UniFrac is a β-diversity measure that uses phylogenetic information to compare environmental samples. UniFrac, coupled with standard multivariate statistical techniques including principal coordinates analysis (PCoA), identifies factors explaining differences among microbial communities.

What does unweighted UniFrac measure?

Unweighted UniFrac measures the distance between two communities by calculating the fraction of the branch length in a phylogenetic tree that leads to descendants in either, but not both, of the two communities (Fig. 1A).

What is unweighted UniFrac distance?

There are two versions of UniFrac distances: an unweighted UniFrac distance that considers only species presence and absence information and counts the fraction of branch length unique to either community, and a weighted UniFrac distance that uses species abundance information and weights the branch length with …

Is UniFrac a Euclidean?

The use of ratio weighting for UniFrac produces measurements that violate the metric triangle inequality, such that Euclidean statistics are technically invalid. Thus this metric, like the Bray-Curtis metric, is a dissimilarity, not a distance.

What is a weighted UniFrac?

Weighted-UniFrac takes into account the relative abundance of species/taxa shared between samples, whereas unweighted-UniFrac only considers presence/absence. Default is FALSE , meaning the unweighted-UniFrac distance is calculated for all pairs of samples.

What is the difference between weighted and unweighted UniFrac?

Is Bray Curtis phylogenetic?

First, the Bray-Curtis dissimilarity creates a matrix in function of the how much the samples are different. Whereas the UniFrac measures the phylogenetic distance between sets of taxa in a phylogenetic tree as the fraction of the branch length of the tree that leads to descendants from either one environment.

What does an NMDS plot show?

Non-metric Multi-dimensional Scaling (NMDS) is a way to condense information from multidimensional data (multiple variables/species/OTUs), into a 2D representation or ordination. NMDS plots are non-metric, meaning that among other things, they use data that is not required to fit a normal distribution.