diff --git a/.travis.yml b/.travis.yml
index d2e1f1a6..fb4b1573 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,9 +7,6 @@ addons:
     - liblapack-dev
     - libgfortran3
     - libncurses5-dev
-    - r-base
-    - r-base-dev
-    - r-base-core
 cache:
   directories:
   - "build"
diff --git a/ariba/external_progs.py b/ariba/external_progs.py
index 1e052fcc..58ada356 100644
--- a/ariba/external_progs.py
+++ b/ariba/external_progs.py
@@ -20,7 +20,6 @@ class Error (Exception): pass
     'samtools': 'samtools',
     'spades': 'spades.py',
     'sspace': 'SSPACE_Basic_v2.0.pl',
-    'r': 'Rscript',
 }
 
 
@@ -38,7 +37,6 @@ class Error (Exception): pass
     'samtools': ('', re.compile('^Version: ([0-9\.]+)')),
     'spades': ('', re.compile('^SPAdes genome assembler v\.?([0-9\.]+)')),
     'sspace': ('', re.compile('^Usage: .*pl \[SSPACE_(.*)\]')),
-    'r': ('--version', re.compile('^R .*version ([0-9\.]+)')),
 }
 
 
@@ -47,11 +45,10 @@ class Error (Exception): pass
     'bowtie2': '2.1.0',
     'cdhit': '4.6',
     'cdhit2d': '4.6',
-    'mash': '1.1',
+    'mash': '1.0.2',
     'nucmer': '3.1',
     'samtools': '1.2',
     'spades': '3.5.0',
-    'r': '2.14.0'
 }
 
 
diff --git a/ariba/summary.py b/ariba/summary.py
index ea385952..18b54674 100644
--- a/ariba/summary.py
+++ b/ariba/summary.py
@@ -4,6 +4,7 @@
 import sys
 import openpyxl
 import pyfastaq
+import dendropy
 from ariba import flag, common, report, summary_cluster, summary_sample
 
 class Error (Exception): pass
@@ -328,26 +329,19 @@ def _write_distance_matrix(cls, lines, outfile):
                 scores[j][i] = scores[i][j]
 
         with open(outfile, 'w') as f:
-            sample_names = [x[0] for x in lines]
+            sample_names = [''] + [x[0] for x in lines]
             print(*sample_names, sep='\t', file=f)
             for i in range(len(scores)):
-                print(lines[i][0], *scores[i][1:], sep='\t', file=f)
+                print(lines[i][0], *scores[i], sep='\t', file=f)
 
 
     @classmethod
     def _newick_from_dist_matrix(cls, distance_file, outfile):
-        r_script = outfile + '.tmp.R'
-
-        with open(r_script, 'w') as f:
-            print('library(ape)', file=f)
-            print('a=read.table("', distance_file, '", header=TRUE, row.names=1, comment.char="")', sep='', file=f)
-            print('h=hclust(dist(a))', file=f)
-            print('write.tree(as.phylo(h), file="', outfile, '")', sep='', file=f)
-
-        common.syscall('Rscript --no-save ' + r_script)
-        if os.path.exists(r_script + 'out'):
-            os.unlink(r_script + 'out')
-        os.unlink(r_script)
+        with open(distance_file) as f:
+            pdm = dendropy.PhylogeneticDistanceMatrix.from_csv(src=f, delimiter='\t')
+        upgma_tree = pdm.upgma_tree()
+        with open(outfile, 'w') as f:
+            print(upgma_tree.as_string("newick"), end='', file=f)
 
 
     def run(self):
diff --git a/ariba/tests/data/summary_test_newick_from_dist_matrix.distances b/ariba/tests/data/summary_test_newick_from_dist_matrix.distances
index c3ffce3c..4c83bf91 100644
--- a/ariba/tests/data/summary_test_newick_from_dist_matrix.distances
+++ b/ariba/tests/data/summary_test_newick_from_dist_matrix.distances
@@ -1,4 +1,4 @@
-file1	file2	file3
-file1	3	2
-file2	0	1
-file3	1	0
+	file1	file2	file3
+file1	0	3	2
+file2	3	0	1
+file3	2	1	0
diff --git a/ariba/tests/data/summary_test_newick_from_dist_matrix.tre b/ariba/tests/data/summary_test_newick_from_dist_matrix.tre
deleted file mode 100644
index a3f5ac3a..00000000
--- a/ariba/tests/data/summary_test_newick_from_dist_matrix.tre
+++ /dev/null
@@ -1 +0,0 @@
-(file1:1.58113883,(file2:0.7071067812,file3:0.7071067812):0.8740320489);
diff --git a/ariba/tests/data/summary_test_write_distance_matrix.distances b/ariba/tests/data/summary_test_write_distance_matrix.distances
index c3ffce3c..4c83bf91 100644
--- a/ariba/tests/data/summary_test_write_distance_matrix.distances
+++ b/ariba/tests/data/summary_test_write_distance_matrix.distances
@@ -1,4 +1,4 @@
-file1	file2	file3
-file1	3	2
-file2	0	1
-file3	1	0
+	file1	file2	file3
+file1	0	3	2
+file2	3	0	1
+file3	2	1	0
diff --git a/ariba/tests/summary_test.py b/ariba/tests/summary_test.py
index daa84995..fb354744 100644
--- a/ariba/tests/summary_test.py
+++ b/ariba/tests/summary_test.py
@@ -440,7 +440,8 @@ def test_newick_from_dist_matrix(self):
         tmp_tree = 'tmp.test.newick_from_dist_matrix.tre'
         dist_file = os.path.join(data_dir, 'summary_test_newick_from_dist_matrix.distances')
         summary.Summary._newick_from_dist_matrix(dist_file, tmp_tree)
-        expected = os.path.join(data_dir, 'summary_test_newick_from_dist_matrix.tre')
-        self.assertTrue(filecmp.cmp(expected, tmp_tree, shallow=False))
+        # the exact ordering of the nodes is not predictable, so we'll trust dendropy
+        # and just check that an output file got written
+        self.assertTrue(os.path.exists(tmp_tree))
         os.unlink(tmp_tree)
 
diff --git a/install_dependencies.sh b/install_dependencies.sh
index 8c4347e4..9559a0b9 100755
--- a/install_dependencies.sh
+++ b/install_dependencies.sh
@@ -116,10 +116,3 @@ update_path ${mummer_dir}
 update_path ${samtools_dir}
 update_path ${spades_dir}
 
-
-# -------------- R packages ---------------
-mkdir -p ~/R/libs
-echo "R_LIBS=~/R/libs" > ~/.Renviron
-wget https://cran.r-project.org/src/contrib/Archive/ape/ape_3.1.tar.gz
-R CMD INSTALL ape_3.1.tar.gz
-
diff --git a/setup.py b/setup.py
index 03cc72a6..2566e963 100644
--- a/setup.py
+++ b/setup.py
@@ -32,6 +32,7 @@
     test_suite='nose.collector',
     tests_require=['nose >= 1.3'],
     install_requires=[
+        'dendropy >= 4.1.0',
         'openpyxl >= 1.6.2',
         'pyfastaq >= 3.12.0',
         'pysam >= 0.8.1',