diff --git a/scripts/gtdb_training_set.py b/scripts/gtdb_training_set.py
index e1b3aa2..dd68f67 100755
--- a/scripts/gtdb_training_set.py
+++ b/scripts/gtdb_training_set.py
@@ -23,6 +23,7 @@
 import logging
 import argparse
 import gzip
+import random
 from collections import defaultdict
 from dataclasses import dataclass
 
@@ -65,25 +66,37 @@ def __init__(self):
         # genomes to retain without needing to pass QC
         self.QC_EXCEPTIONS = set(['G015697925']) # s__Pinguicoccus supinus representative genome
 
+        # maximum number of genomes to select per species
+        self.MAX_PER_SPECIES = 100
+
         self.log = logging.getLogger('timestamp')
 
-    def parse_metadata_file(self, gtdb_metadata_file: str) -> dict:
+    def parse_metadata_file(self, gtdb_metadata_file: str) -> tuple[dict, dict]:
         """Parse manual ground truth file."""
 
         genome_data = {}
+        gtdb_sp_rid = {}
         open_file = gzip.open if gtdb_metadata_file.endswith('.gz') else open 
         with open_file(gtdb_metadata_file, 'rt') as f:
             header = f.readline().strip().split('\t')
+
             gid_idx = header.index("accession")
             gtdb_taxonomy_idx = header.index('gtdb_taxonomy')
             ncbi_taxonomy_idx = header.index('ncbi_taxonomy')
 
+            gtdb_rep_idx = header.index('gtdb_representative')
+
             for line in f:
                 tokens = line.strip().split('\t')
                 gid = canonical_gid(tokens[gid_idx])
                 genome_data[gid] = GenomeData(tokens[gtdb_taxonomy_idx], tokens[ncbi_taxonomy_idx])
 
-        return genome_data
+                is_rep = tokens[gtdb_rep_idx].lower().startswith('t')
+                if is_rep:
+                    gtdb_sp = [t.strip() for t in tokens[gtdb_taxonomy_idx].split(';')][-1]
+                    gtdb_sp_rid[gtdb_sp] = gid
+
+        return genome_data, gtdb_sp_rid
 
     def parse_taxonomy_file(self, taxonomy_file: str) -> dict:
         """Parse taxonomy file."""
@@ -175,12 +188,33 @@ def run(self, gtdb_bac_metadata_file: str,
 
         # parse genomes from GTDB metadata files
         self.log.info('Parsing GTDB metadata files:')
-        gtdb_bac_gids = self.parse_metadata_file(gtdb_bac_metadata_file)
-        gtdb_ar_gids = self.parse_metadata_file(gtdb_ar_metadata_file)
+        gtdb_bac_gids, gtdb_bac_sp_rid = self.parse_metadata_file(gtdb_bac_metadata_file)
+        gtdb_ar_gids, gtdb_ar_sp_rid = self.parse_metadata_file(gtdb_ar_metadata_file)
         gtdb_gids = {**gtdb_bac_gids, **gtdb_ar_gids}
-        self.log.info(f' - identified {len(gtdb_bac_gids):,} bacterial genomes')
-        self.log.info(f' - identified {len(gtdb_ar_gids):,} archaeal genomes')
-        self.log.info(f' - identified {len(gtdb_gids):,} total genomes')
+        gtdb_sp_rid = {**gtdb_bac_sp_rid, **gtdb_ar_sp_rid}
+        self.log.info(f' - identified {len(gtdb_bac_gids):,} bacterial genomes from {len(gtdb_bac_sp_rid):,} species')
+        self.log.info(f' - identified {len(gtdb_ar_gids):,} archaeal genomes from {len(gtdb_ar_sp_rid):,} species')
+        self.log.info(f' - identified {len(gtdb_gids):,} total genomes from {len(gtdb_sp_rid):,} species')
+
+        # subsample to maximum number of genomes per species
+        self.log.info(f'Sampling to {self.MAX_PER_SPECIES} genomes per species:')
+
+        sp_gids = defaultdict(set)
+        for gid, genome_data in gtdb_gids.items():
+            gtdb_sp = [t.strip() for t in genome_data.gtdb_taxonomy.split(';')][-1]
+            sp_gids[gtdb_sp].add(gid)
+        
+        gtdb_gids_sampled = {}
+        for sp, gids in sp_gids.items():
+            if len(gids) > self.MAX_PER_SPECIES:
+                rid = gtdb_sp_rid[sp]
+                gids.remove(rid)
+                gids = [rid] + random.sample(list(gids), self.MAX_PER_SPECIES - 1)
+
+            for gid in gids:
+                gtdb_gids_sampled[gid] = gtdb_gids[gid]
+
+        self.log.info(f' - retained {len(gtdb_gids_sampled):,} genomes for training')
 
         # read NCBI taxonomy for genomes
         self.log.info('Parsing NCBI taxonomy file:')
@@ -198,7 +232,7 @@ def run(self, gtdb_bac_metadata_file: str,
 
         # combine all training genomes
         self.log.info('Combining all genomes to use for training:')
-        training_gids = {**gtdb_gids, **gtdb_reassigned_gids}
+        training_gids = {**gtdb_gids_sampled, **gtdb_reassigned_gids}
         self.log.info(f' - identified {len(training_gids):,} total genomes for training')
 
         # sanity check that all genomes that are a QC expection are accounted for