Hierarchical clustering analysis of rhizobia based on a heat map of 210 genes chosen from Mesorhizobium core genes. Gene homologs were chosen on the basis of BLASTP results (E-value ≤1 ×10−5; identity ≤ 35%). Homolog presence and absence are indicated by yellow and red, respectively. The five genera for which multiple genomes were available are indicated in different colors. The numbers on the dendrogram represent bootstrap values.