Molecular evidence and phylogenetic affiliations of Wolbachia in cockroaches.

Wolbachia is a genus of obligate intracellular bacteria in the Anaplasmataceae family of the -Proteobacteria that are transmitted through the egg cytoplasm and manipulate reproduction in their hosts in various ways (Werren, 1997). Wolbachia are associated with cytoplasmic incompatibility, parthenogenesis, feminization and male killing in arthropods and these aspects have been adequately reviewed recently (Charlat et al., 2003). Wolbachia are considered as potent evolutionary force, especially since these also harbor active bacteriophages like WO-A and WO-B, leading even to speciation in arthropods through eVects such as reproductive isolation caused by cytoplasmic incompatibility (Shoemaker et al., 1999; Hurst and Werren, 2001; Charlat et al., 2003; Bordenstein and Wernegreen, 2004; Jaenike et al., 2006). Wolbachia are presently known from a large variety of arthropods and a few species of nematode worms. Among arthropods, Wolbachia are known to be widely distributed in insects; the other groups being mites, spiders and terrestrial Crustacea (or Isopoda). In a survey of Wolbachia in diVerent groups of insects from Panama, Werren et al. (1995) showed that over 16% of the species are infected. In a subsequent survey of temperate North American insects, Werren and Windsor (2000) found over 19% of the insect species to be infected with this endosymbionts. A further report by Jeyaprakash and Hoy (2000), using ‘long PCR’ modiWcation, demonstrated that Wolbachia is present in over 76% of the arthropods tested. A survey of Japanese