Phylogenetic analysis of Blattabacterium, endosymbiotic bacteria from the wood roach, Cryptocercus (Blattodea:...

Members of the cockroach genus Cryptocercus are wood-feeding, subsocial insects that live in temperate forests of the Nearctic and Palaearctic. At present, nine species are recognized: Cryptocercus relictus and Cryptocercus kyebangensis in eastern Asia and Russia, Cryptocercus primarius and Cryptocercus matilei in southwestern China, Cryptocercus clevelandi in the western USA, and Cryptocercus darwini, Cryptocercus garciai, Cryptocercus punctulatus, and Cryptocercus wrighti in the eastern USA. Like all extant cockroaches, Cryptocercus harbor endosymbiotic bacteria, Blattabacterium, in their fat bodies. The endosymbionts in all cockroaches have been considered a single species, Blattabacterium cuenoti, since their discovery about a century ago. However, a recent analysis of DNA sequences from representatives of four cockroach families has indicated that there is considerable DNA sequence divergence among B. cuenoti from different host species. As a part of our studies on the evolution of Cryptocercus, we examined DNA sequence divergence among B. cuenoti from six of the nine known Cryptocercus species. Specifically, we sequenced approximately 2,400 bp of the 16S rRNA and 23S rRNA genes of B. cuenoti from six species of Cryptocercus. We found that B. cuenoti in Cryptocercus has differentiated into multiple monophyletic lineages distinguishable by DNA sequence of rRNA genes and host association. Our sequence divergence estimates were consistent with those reported for other, congeneric bacterial species. We propose the recognition of three new species of Blattabacterium within Cryptocercus species as follows: Blattabacterium relictus sp. nov. in C. relictus, Blattabacterium clevelandi sp. nov. in C. clevelandi, and Blattabacterium punctulatus sp. nov. in C. darwini, C. garciai, C. punctulatus, and C. wrighti.