A phylogenetic analysis of filarial nematodes: comparison with the phylogeny of Wolbachia endosymbionts

Infection with the endosymbiotic bacteria Wolbachia is widespread in filari al nematodes. Previous studies have suggested concordance between the phylo geny. of Wolbachia with that of their nematode hosts. However, there is onl y one published molecular phylogenetic study of filarial species, based on the 5S rRNA gene spacer. The phylogeny proposed by this study is partially incongruent with previous classifications of filarial nematodes, based on m orphological characters. Furthermore, both traditional classifications and molecular phylogenies are, in part, inconsistent with the phylogeny of Wolb achia. Here we report mitochondrial cytochrome oxidase I (COI) gene sequenc es for 11 species of filaria and for another spirurid nematode which was in cluded as an outgroup. In addition, 16S rRNA, wsp and ftsZ gene sequences w ere generated fur the Wolbachia of several filarial species, in order to co mplete the available data sets and further resolve the phylogeny of Wolbach ia in nematodes. We used these data to evaluate whether nematode and Wolbac hia phylogenies are concordant. Some of the possible phylogenetic reconstru ctions based on COI gene were congruent with the phylogeny of Wolbachia and supported the grouping of the rodent filaria Litomosoides sigmodontis with the lymphatic filariae (i.e. Brugia spp. and Wuchereria spp.) and the sist er group relationship of Dirofilaria spp. and Onchocerca spp. However, the placement of the Wolbachia-free filaria Acanthoeilonema viteae is ambiguous and dependent on the phylogenetic methods used.