How to make Co-phylogeny plot: easy tanglegram in R

Tanglegrams are co-phylogeny which is a very powerful visualization tool to examine co-evolution. Here is a tutorial on how to make them in R.

Tanglegram is a representation of co-phylogeny where two phylogenetic trees are linked. This method is super useful to visualize common traits shared by both trees. For example, it can be used to visualize host-pathogen (or host-symbiotic) evolution and visualize if there is any phylogenetic concordance between the two phylogenetic trees.

I was in need to visualize co-phylogeny of phylogenetic tree reconstructed from chromosomal and symbiotic genes. Surprisingly, I didn’t find any strait-forward solution in R that can be used for drawing tanglegram. Particularly I wanted to leverage the beautiful ggtree library. After trying out several methods, I found the following approach works well for me so far.

In this post, I’m going to use two toy trees with the following Newick format. Note that they have the same isolate, but different tree-topology (since supposedly different gene-set were used to reconstruct them).

Tree 1: (((((((A:4,B:4):6,C:5):8,D:6):3,E:21):10,((F:4,G:12):14,H:8):13):13,((I:5,J:2):30,(K:11,L:11):2):17):4,M:56);
Tree 2: (((((((F:8,I:18,G:4):2,C:5):3,M:6):3,E:21):10,((A:2,B:2):4):3):13,((K:5,L:2):20,(H:18,J:11):2):17):4,D:56);

We might be interested to visualize one (or more) interesting feature(s) (i.e. genotype) associated with the isolates in both trees. Our meta-file looks like the following:

IsolateGenotype
AGreen
BGreen
CGreen
DGreen
ERed
FRed

Let’s load the necessary packages.

library(ggplot2)
library(ggtree)
library(phangorn)
library(dplyr)

The best thing about ggtree is you can attach any feature(s) associated with isolates using a simple CSV file. Just make sure that the first column of your metafile has the same isolate names as used in the tree. Let’s load the metafile and both phylogenetic tree to be used. I also like to do midpoint rooting at this point.

# Meta file
meta <- read.table('~/path/to/meta.csv', sep=',', header = T)

# Load tree 1
tree1 <- read.tree('~/path/to/tree1.nwk')
tree1 <- midpoint(tree1)

# Load tree 2
tree2 <- read.tree('~/path/to/tree2.nwk')
tree2 <- midpoint(tree2)

Let’s combine the meta feature dataset with both phylogenetic trees and visualize how they look.

t1 <-ggtree(tree1)  %<+%  meta + geom_tiplab()
t2 <- ggtree(tree2)  %<+%  meta + geom_tiplab()

t1
t2

Now we are going to draw both trees in a single figure. We also want to flip tree 2, for which we need to change the x-coordinates in that tree.

d1 <- t1$data
d2 <- t2$data

d1$tree <-'t1'
d2$tree <-'t2'

d2$x <- max(d2$x) - d2$x + max(d1$x) +  max(d1$x)*0.3
pp <- t1 + geom_tree(data=d2)
pp 

In the above code block, we are grabbing the backend data frame from both trees and updating the tree 2 data frame x-coordinate. We are using this equation for the update: max(d2$x) - d2$x + max(d1$x) + max(d1$x)*0.3. You can toy with different values depending on the branch length unit of your tree to get good visualization (I particularly suggest changing max(d1$x)*0.3 terms).

Two phylogenetic trees, face-to-face.

Let’s join d1 and d2 for dataset so that we can use the coordinates of the tips for making connections between both of the trees.

dd <- bind_rows(d1, d2) %>% 
  filter(isTip == TRUE)
dd1 <- as.data.frame(dd) 

Now, we are going to conditionally join the tips of both trees for the feature we are interested in. Connected tips will represent the same isolates.

green_tree <- dd1[which(dd1$Genotype == 'Green'), c('label', 'x', 'y', 'tree')]
pp + geom_line(aes(x, y, group=label), data=green_tree, color='#009E73') 

Connecting the isolates

Lily asked in the comment section if it is possible to connect all the tip labels from both trees. The previous code chunk actually connects the tips based on a subset from meta. In this case, we do not have to do any kind of subsetting. Using the following code we can connect all tips:

pp + geom_line(aes(x, y, group=label), data=dd1)

Here, label is the tip-label variable, which is already associated with cophylogeny. You can check it by head(pp$dd1)

This may look messy since I am using totally random trees. However, if your co-phylogeny trees have some particular pattern, the tanglegram will show that.

15 thoughts on “How to make Co-phylogeny plot: easy tanglegram in R”

  1. Hi, this is really great. Thanks for sharing it with us. I ma wondering if it is possible to subset basing on what is present in both data sets i.e., x > 0 in both A and B data sets?

    1. Hi, thanks for commenting. If I understand your question correctly, you can make a new column based on a condition of interest, and use the new column to subset and plot connected lines.

  2. Hi! Is there a way to rotate nodes on the trees? I rotate them before adding the meta data to the tree file but I keep getting the same tree order.

    Also, is there also a way to make the lines different colors, like make each clade a different color?

    Thank you

  3. Is there anyway to connect the line from the end of the tip label to the other tree so the line does not cross thru the tip label? Thanks1

  4. What if you have two different trees that do not have the same tip labels. For example a phylogenetic tree based on a core genome and then a protein based tree and then you want to show which genomes in the core tree that harbours the protein in the second tree. Thanks!

    1. That is definitely possible. Please give me some time, and I’ll update the main post. Sorry for the late reply. Best.

    1. Sorry about that! I just added it to the main post:

      dd <- bind_rows(d1, d2) %>%
      filter(isTip == TRUE)
      dd1 <- as.data.frame(dd)

  5. Hi, really clear description of how to draw tanglegrams within R. Would it be possible to extend this to more than two trees?

    1. That is really interesting idea. I think that is technically possible. Let me try that, I’ll come back to you soon! Thanks for reading 🙂

  6. Hi, this is great thanks. How would you edit your code to link the tips from the two trees not by your meta file, but by matching tiplabels? Thanks! Lily

    1. Yes you can do that. You do not need to do any subset, and use the following command in R instead:

      pp + geom_line(aes(x, y, group=label), data=dd1)

      Please check the article, I have updated it!

      Thanks for reading 🙂

Leave a Reply