Comparative genomics from mitochondria, plastids, and mutualistic endosymbiotic bacteria has shown that the stable establishment of a bacterium in a host cell results in genome reduction. Although many highly reduced genomes from endosymbiotic bacteria are stable in gene content and genome structure, organelle genomes are sometimes characterized by dramatic structural diversity. Previous results from Hodgkinia, an endosymbiont of cicadas, revealed that some lineages of this bacterium had split into multiple new cytologically distinct yet genetically interdependent species. In this talk I will outline the diversity of Hodgkinia genomes we have discovered, and show how these processes both parallel and differ from some examples of genome fragmentation and expansion in organelles.