sumt

The command-line program sumt computes consensus trees and other tree-summary statistics for sets of phylogenetic trees. The input trees can be in one or more input files, and will typically be from a Bayesian MCMC analysis (BEAST or MrBayes for instance) or from a bootstrap procedure.

sumt can compute four different kinds of main tree summaries:

• Majority rule consensus tree
• Majority rule consensus tree, with all compatible bipartitions added
• Maximum clade credibility tree
• Maximum bipartition credibility tree

Branch labels on these trees indicate clade support.

sumt also produces a summary of observed bipartitions along with branch length means and variances and, optionally, a list of tree topologies and how frequently they were observed. The name is taken from the sumt command in MrBayes, whose functionality it was originally meant to resemble. Clade support values and topology frequencies can be interpreted as posterior probabilities if the input trees are from a Bayesian MCMC analysis.

Availability

The sumt source code is available on GitHub: https://github.com/agormp/sumt. The executable can be installed from PyPI: https://pypi.org/project/sumt/

Installation

python3 -m pip install sumt

Upgrading to latest version:

python3 -m pip install --upgrade sumt

Citation

To cite sumt: use the link in the right sidebar under About --> Cite this repository.

Dependencies

sumt relies on the phylotreelib library for phylogeny-related matters, and on psutil for (optionally) monitoring memory usage. These are automatically included when using pip to install.

Overview

• Input:
  • One or more files containing phylogenetic trees (all trees must have same leaf names), in NEXUS or Newick format.
  • Typically trees are from a Bayesian MCMC analysis, but could also be from a bootstrap procedure
  • Can read sample files from BEAST and MrBayes
• Output:
  • File containing summary tree with clade support values (= frequency of bipartition or clade in input trees).
    • The summary tree can be one of these:
      • Majority rule consensus tree
      • Majority rule consensus tree, with all compatible bipartitions added
      • Maximum clade credibility (MCC) tree
      • Maximum bipartition credibility (MBC) tree - this is similar to MCC, but ignoring location of root.
    • The file also contains a second consensus tree where branch labels indicate bipartition IDs, which can be used for interpreting bipartition file below.
  • File containing list of bipartitions (in "*." format) present in input trees, along with mean and variance of corresponding branch lengths. This list includes both bipartitions that correspond to branches in the summary tree, and bipartitions not included in the summary tree (e.g., low frequency bipartitions).
  • During run: progress bar showing percentage of file analyzed
  • (Optionally) File containing list of observed tree topologies with posterior and cumulated probabilities
• Optimized for speed and memory usage:
  • Consensus tree computed from 100,000 trees with 41 leaves in 28 s, using max 49 MB memory on 2021 MacBook (4,440 distinct bipartitions seen)
  • Same file processed in 30 s, using max 2.83 GB memory when also keeping track of topologies (74,283 distinct topologies seen)
• Option to discard fraction of trees as burn-in (for Bayesian analyses)
• Option to compute average standard deviation of split frequencies when multiple input files are given. This can be used as a measure of convergence of Bayesian analyses, assuming that different files represent independent MCMC chains.
• Option to include all compatible bipartitions in consensus tree (in addition to those that are present in more than 50% of input trees).
• Options to root consensus tree using either outgroup, midpoint, minimum variance rooting, or based on where root is most frequently placed in input tree sample
• Option to set node depths to mean of those observed in input trees (only useful when input trees are based on clock model)
• Option to set node depths using "common ancestor heights" in input trees (same as "treeannotator -heights ca" in the BEAST2 package; only useful when input trees are based on clock model)
• Option to assign specific weights to different input files.
• Option to automatically assign weights so all files have equal impact regardless of number of trees in them.
• Option to set basename of output files (default: basename will be stem of input file name)
• Program prints information about run to stdout:
  • Number of leaves on tree
  • Number of different toplogies seen in input trees (if also using option -t)
  • Number of bipartitions or clades seen in input trees, along with theoretical maximum
  • Number of bipartitions in summary tree, along with theoretical maximum
  • Indication of whether summary tree is resolved
  • Indication of whether summary tree has been explicitly rooted and how
  • Log credibility (sum of logs of bipartition or clade frequencies in summary tree)
  • Indication of how branch lengths have been set
  • Root credibility (when input trees are clock trees)
  • Report of maximum memory usage during processing

Usage

``` usage: sumt [-h] [--version] [--con | --all | --mcc | --mbc] [--noblen | --biplen | --meandepth | --cadepth] [--rootmid | --rootminvar | -r TAXON [TAXON ...] | --rootfile FILE | --rootmaxfreq] [-b NUM] [-t NUM] [-s] [-f NUM] [-n] [-v] [-q] [--basename NAME] [--autow] [--informat FORMAT] [-i FILE | -w WEIGHT FILE]

Computes summary tree and statistics from set of phylogenetic trees

options: -h, --help show this help message and exit --version show the program's version number and exit

Type of summary tree (pick one option): --con majority rule consensus tree --all majority rule consensus tree with all compatible bipartitions added --mcc Maximum Clade Credibility (MCC) tree. The MCC tree is determined by inspecting tree samples and selecting the tree that has the highest product of clade frequencies (= highest sum of log of clade frequencies). The MCC tree is therefore a tree that has been observed in the pool of tree samples, differing from the consensus tree which typically does not match any individual sample. NOTE 1: only meaningful if input trees are estimated using clock model. NOTE 2: by default, the MCC tree uses the rooting of the specific tree sample. This will often (but not always) correspond to the bipartition where the root is most commonly found in the input trees. --mbc Maximum Bipartition Credibility (MBC) tree. The MBC tree is similar to the MCC tree but counting bipartitions instead of clades, i.e. ignoring rooting (two input trees can have the same set of bipartitions, but be rooted in different locations).

Estimation of branch lengths (pick one option): --noblen Do not set branch lengths (only the topology and branch- or clade- support of the summary tree are estimated). --biplen Set branch lengths in summary tree based on average for corresponding leaf bipartitions:each branch in tree corresponds to a bipartition of the leaves into two groups. Branch lenghts are set to the mean of the length of thecorresponding bipartition across all input trees. --meandepth set node depth for each clade to mean node depth observed for that clade among input trees (and branch lengths are then based on these depths). Warning: option is intended for input trees estimated using a clock model. It requires that all clades in the summary tree have been observed in the input trees, and may fail for some rootings.NOTE: mean is computed across trees where the specific, monophyletic clade is present, and may therefore be based on very few (down to one) values. NOTE 2: may result in negative branch lengths. --cadepth 'Common Ancestor depth'. Same as option '--height ca' in treeannotator. Uses all trees in input set when determining node- depths. For a given clade: (1) Find the most recent common ancestor of the leaves in that clade in each of the input trees. (2) Compute node-depth of clade as the mean of the depths of these MRCAs. This is different from --meandepth where only trees with that exact clade are included when computing the mean. Warning: option is intended for input trees estimated using a clock model. It requires that all clades in the summary tree have been observed in the input trees, and may fail for some rootings.

Rooting of summary tree: --rootmid perform midpoint rooting of summary tree --rootminvar perform minimum variance rooting of summary tree -r TAXON [TAXON ...] root summary tree on specified outgroup taxon/taxa --rootfile FILE root summary tree on outgroup taxa listed in file (one name per line) --rootmaxfreq root summary tree on bipartition where root is located most frequently in input trees. NOTE: only meaningful if input trees are estimated using clock model

Bayesian phylogeny options: -b NUM [NUM ...] burnin: fraction of trees to discard [0 - 1; default: 0.0]. Either one value (used on all input files), or one value per input file. -t NUM compute tree probabilities, report NUM percent credible interval [0 - 1] -s compute average standard deviation of split frequencies (ASDSF) -f NUM Minimum frequency for including bipartitions in report and in computation of ASDSF [default: 0.1]

Output to terminal and files: -n no warning when overwriting files -v verbose: show full traceback in the event of failed python execution -q quiet: don't print progress indication to terminal window. NOTE: also turns on the -n option --basename NAME base name of output files (default: derived from input file)

Other options: --autow automatically assign file weights based on tree counts, so all files have equal impact (default is for all trees, not files, to be equally important) --informat FORMAT format of input files: nexus, newick [default: nexus]

Input tree files: -i FILE input FILE(s) containing phylogenetic trees (repeat -i FILE option for each input file) -w WEIGHT FILE input FILEs with specified weights (repeat -w WEIGHT FILE option for each input file) ```

Usage examples

Example 1:

Majority rule consensus tree, bipartition summary, topology summary, computation of average standard deviation of split frequencies, midpoint rooting

The command below causes sumt to do the following:

• --con: Compute majority rule consensus tree
• -b 0.25: Discard 25% of tree samples as burn-in
• -t 0.99: Keep track of topology probabilities, report 99% credible set
• -s: Compute average standard deviation of split frequencies as a measure of MCMC convergence (asdsf)
• -f 0.1: Include bipartitions seen in more than 10% of input trees for computations of (1) asdsf and of (2) branch lengt mean, variance, and standard error of the mean
• --rootmid: Perform midpoint rooting
• --biplen: Set branch lengths to mean of those observed for the corresponding bipartitions in input trees
• -i primates.run1.t -i primates.run2.t: Summarise the tree samples in the files primates.run1.t and primates.run2.t

sumt --con -b 0.25 -t 0.99 -f 0.1 --rootmid --biplen -i primates.run1.t -i primates.run2.t

Screen output

This is printed to screen during run:

``` Counting trees in file tests/primates.run1.t 2,001 Counting trees in file tests/primates.run2.t 2,001

Analyzing file: tests/primates.run1.t (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Analyzing file: tests/primates.run2.t (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Computing consensus tree...done. Consensus tree written to primates.con Bipartition list written to primates.parts Tree probabilities written to primates.trprobs

Number of leaves on input trees: 5 Different topologies seen: 3 Different bipartitions seen: 4 (theoretical maximum: 6) Bipartitions in Consensus tree: 2 (theoretical maximum: 2) (tree is fully resolved - no polytomies)

Consensus tree has been midpoint-rooted

Branch lengths set based on mean branch lengths for corresponding bipartitions

Log bipartition credibility: -0.028723

Done. 3,002 trees analyzed. Time spent: 0:00:00 (h:m:s) Max memory used: 31.91 MB. ```

Bipartition overview

Below are the contents of the file primates.parts, which lists information about bipartitions observed in input trees. A bipartition - or split - is a division of leaf-names into two groups: those on one side of an internal branch, and those on the other side. Two trees with different topologies can have the same bipartition, and that internal branch is then said to have been observed in both trees. sumt keeps track of bipartition frequencies, as well as means and variances of the lengths of the corresponding branches. For branches included on the summary tree, the clade support value is the same as the value in the column PROB (i.e., the frequency of the bipartion among the input trees).

Bipartitions are indicated using the "asterisk and dots" notation also used by e.g. MrBayes: Columns correspond to taxa (with column 1 = taxon 1). All taxa with "*" (or ".") are in the same half of the bipartition. The ID column contains either a leaf name or a numerical branchID that corresponds to branch labels given in the second tree in the consensus tree file (in this case there are 5 leaves, and therefore only two internal branches). Branch IDs are numbered consecutively in order of bipartition frequency (so the branch with ID=7 has the 7th highest observed bipartition frequency).

``` List of bipartitions:

PART = Description of partition in .* format PROB = Posterior probability of the partition BLEN = Mean branch length VAR = Branch length variance SEM = Standard error of the mean for branch length ID = Leaf name or internal branch label, for those bipartitions that are included in consensus tree

PART PROB BLEN VAR SEM ID .... 1.000000 0.07561 (0.0003703) (0.0003512) Chimpanzee .... 1.000000 0.3551 (0.01894 ) (0.002512 ) Gibbon .... 1.000000 0.0728 (0.0005512) (0.0004285) Gorilla .... 1.000000 0.05689 (0.0002746) (0.0003025) Human ....* 1.000000 0.2793 (0.008997 ) (0.001731 ) Orangutan ... 1.000000 0.1464 (0.003637 ) (0.001101 ) 6 ... 0.971686 0.03674 (0.0004015) (0.000371 ) 7 ```

Tree probabilities

This is the content of the file primates.trprobs. In this case there were only 5 leaves corresponding to a total of 15 possible trees, of which 3 were seen in the MCMC samples. Note: For data sets with more than about 15-20 taxa, each sampled tree will typically be unique and all topologies therefore have the same probability, meaning the credible set is not very useful. (Bipartitions or clades on those trees will, however, not be unique, and clade probabilities carry useful information).

```

NEXUS

[This file contains the 99% most probable trees found during the MCMC search, sorted by posterior probability (the 99% HPD interval). Lower case 'p' indicates the posterior probability of a tree. Upper case 'P' indicates the cumulative posterior probability.]

begin trees; translate 1 Chimpanzee, 2 Gibbon, 3 Gorilla, 4 Human, 5 Orangutan ; tree tree1 [p = 0.971686] [P = 0.971686] = ((3,(5,2)),1,4); tree tree2 [p = 0.014990] [P = 0.986676] = ((5,2),(3,1),4); tree tree_3 [p = 0.013324] [P = 1.000000] = (((5,2),1),3,4); end; ```

Consensus tree

This is the content of the file primates.con. The difference between the two trees is the information given as branch labels:

• First tree: labels are bipartition frequencies (= posterior probability of bipartition, if tree samples are from Bayesian MCMC analysis)
• Second tree: labels are the branchIDs also indicated in the bipartition summary in the file primates.parts. This should make it simpler to understand what branch the bipartition corresponds to (open the tree file in a treeviewer such as FigTree and view the branch labels).

```

NEXUS

begin trees; [In this tree branch labels indicate the posterior probability of the bipartition corresponding to the branch.] tree prob = ((Orangutan:0.279279,(Gorilla:0.0728019,(Chimpanzee:0.0756054,Human:0.0568895)0.972:0.0367431)1.000:0.146428):0.0758066,Gibbon:0.355086);

[In this tree branch labels indicate the bipartition ID listed in the file primates.parts. These branch labels can be used for interpreting the table of branch lenght info in that file] tree partID = ((Orangutan:0.279279,(Gorilla:0.0728019,(Chimpanzee:0.0756054,Human:0.0568895)7:0.0367431)6:0.146428):0.0758066,Gibbon:0.355086); end; ```

Example 2:

Maximum bipartition credibility tree, topology summary, setting basename of output files

The command below causes sumt to do the following:

• --mbc: Compute maximum bipartition credibility tree. The MBC tree is determined by inspecting tree samples and selecting the tree that has the highest product of bipartition frequencies (= highest sum of log of bipartition frequencies). This is similar to the MCC (maximum clade credibility) but counting bipartitions instead of monophyletic clades (i.e., ignoring rooting).
• -b 0.1: Discard 10% of tree samples as burn-in
• -t 0.75: Report 75% credible set of topologies (i.e., all the most frequently seen topologies to a cumulated probability of 75%)
• -n: Overwrite any existing output files with no warning
• --basename /Users/bob/hiv: produce output files with the indicated stem (/Users/bob/hiv.parts, /Users/bob/hiv.trprobs, /Users/bob/hiv.mbc)
• --biplen: Set branch lengths to mean of those observed for the corresponding bipartitions in input trees
• -i gp120.trees: Summarise the tree samples in the file gp120.trees

sumt --mbc -b 0.1 -t 0.75 -n --basename /Users/bob/hiv --biplen -i gp120.trees

Example 3:

Consensus tree with all compatible bipartitions, outgroup rooting

The command below causes sumt to do the following:

• --all: Compute majority rule consensus tree with all compatible bipartitions added (bipartitions with frequency < 50% are checked for compatitibiliy with tree iteratively in order of decreasing frequencies, and added if possible. Iteration stops when the consensus tree is fully resolved or all bipartitions have been checked)
• -b 0.1: Discard 10% of tree samples as burn-in
• -t 0.95: Report 95% credible set of topologies (i.e., all the most frequently seen topologies to a cumulated probability of 95%)
• -n: Overwrite any existing output files with no warning
• -r macaque olive_baboon yellow_baboon: root consensus tree using outgroup consisting of the taxa "macaque", "olivebaboon", and "yellowbaboon".
• --biplen: Set branch lengths to mean of those observed for the corresponding bipartitions in input trees
• -i mhc_align.run1.t: Summarise the tree samples in the file mhc_align.run1.t

sumt --all -b 0.1 -t 0.95 -n -r macaque olive_baboon yellow_baboon ---biplen i mhc_align.run1.t

Example 4:

Maximum clade credibility tree with "common ancestor" node depths, separate burnins

The command below causes sumt to do the following:

• --mcc: Compute maximum clade credibility tree. Note: input trees need to be based on a clock model for this to be meaningful.
• -b 0.25 0.4: Discard 25% of tree samples in first file, and 40% of trees in second file as burn-in
• --cadepth: set node depth for each clade to mean node depth observed for MRCA of that clade among input trees (this is the same as treeannotator -heights ca in the BEAST2 package). Note: only meaningful when input trees are clock trees.
• -n: Overwrite any existing output files with no warning
• -s: Compute average standard deviation of clade frequencies as a measure of MCMC convergence
• --basename beast_summary: produce output files with the indicated stem
• -i beastrun1.trees -i beastrun2.trees: Summarise the tree samples in the files beastrun1.trees and beastrun2.trees

sumt --mcc -b 0.25 0.4 --cadepth -ns --basename beast_summary -i beastrun1.trees -i beastrun2.trees

Screen output

This is printed to screen during run:

``` Counting trees in file tests/beastrun1.trees 2,001 Counting trees in file tests/beastrun2.trees 2,001

Analyzing file: tests/beastrun1.trees (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Analyzing file: tests/beastrun2.trees (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Finding Maximum Clade Credibility tree...done. Computing common ancestor depths...done. Maximum clade credibility tree written to beast_summary.mcc

Number of leaves on input trees: 508 Different clades seen: 193,339 (theoretical maximum: 1,522,014) Bipartitions in MCC tree: 505 (theoretical maximum: 505) (tree is fully resolved - no polytomies)

MCC tree rooted at original root of tree sample having highest clade credibility Root credibility (frequency of root bipartition in input trees): 86.3%

Branch lengths set based on common ancestor depths in input trees

Highest log clade credibility: -1253.6 Average standard deviation of split frequencies: 0.022985

Done. 3,002 trees analyzed. Time spent: 0:00:31 (h:m:s) Max memory used: 2.15 GB. ```

Example 5:

Maximum clade credibility tree with mean node depths

The command below causes sumt to do the following:

• --mcc: Compute maximum clade credibility tree. Note: input trees need to be based on a clock model for this to be meaningful.
• -b 0.25: Discard 25% of tree samples as burn-in
• --meandepth: set node depth for each clade to mean node depth observed for that specific, monophyletic clade among input trees (this is the same as treeannotator -heights mean in the BEAST2 package). Note: only meaningful when input trees are clock trees.
• -n: Overwrite any existing output files with no warning
• -s: Compute average standard deviation of clade frequencies as a measure of MCMC convergence
• --basename beast_summary: produce output files with the indicated stem
• -i beastrun1.trees -i beastrun2.trees: Summarise the tree samples in the files beastrun1.trees and beastrun2.trees

sumt --mcc -b 0.25 --meandepth -ns --basename beast_summary -i beastrun1.trees -i beastrun2.trees

Example 6:

Maximum bipartition credibility tree with common ancestor node depths, rooted at most frequent position

The command below causes sumt to do the following:

• --mbc: Compute maximum bipartition credibility tree
• -b 0.25: Discard 25% of tree samples as burn-in
• --cadepth: set node depth for each clade to mean node depth observed for MRCA of that clade among input trees (this is the same as treeannotator -heights ca in the BEAST2 package). Note: only meaningful when input trees are clock trees.
• --rootmaxfreq: Root summary-tree at location most frequently observed in input trees
• -n: Overwrite any existing output files with no warning
• -s: Compute average standard deviation of clade frequencies as a measure of MCMC convergence
• --basename beast_summary: produce output files with the indicated stem
• -i beastrun1.trees -i beastrun2.trees: Summarise the tree samples in the files beastrun1.trees and beastrun2.trees

sumt --mbc -b 0.25 --cadepth --rootmaxfreq -ns --basename beast_summary -i beastrun1.trees -i beastrun2.trees

Screen output

This is printed to screen during run:

``` Counting trees in file tests/beastrun1.trees 2,001 Counting trees in file tests/beastrun2.trees 2,001

Analyzing file: tests/beastrun1.trees (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Analyzing file: tests/beastrun2.trees (Weight: 1.000) Discarded 500 of 2,001 trees (burnin fraction=0.25)

Processing trees:

0 10 20 30 40 50 60 70 80 90 100 v-------v-------v-------v-------v-------v-------v-------v-------v-------v-------v

---

Finding Maximum Bipartition Credibility tree...done. Computing common ancestor depths...done. Maximum bipartition credibility tree written to beast_summary.mbc

Number of leaves on input trees: 508 Different bipartitions seen: 193,333 (theoretical maximum: 1,516,010) Bipartitions in MBC tree: 505 (theoretical maximum: 505) (tree is fully resolved - no polytomies)

MBC tree has been rooted at location most frequently observed in input trees Root credibility (frequency of root bipartition in input trees): 86.3%

Branch lengths set based on common ancestor depths in input trees

Highest log bipartition credibility: -1253.45 Average standard deviation of split frequencies: 0.023034

Done. 3,002 trees analyzed. Time spent: 0:00:44 (h:m:s) Max memory used: 2.43 GB. ```