As one of the most widely distributed bacterial cytoplasmic symbionts on earth, Wolbachia pipientis Hertig serves as a model organism for the understanding of host-symbiont interactions. Many mosquito species are infected with Wolbachia strains that induce a form of reproductive manipulation called cytoplasmic incompatibility, in which infected females gain a reproductive advantage over uninfected females in mixed infection populations. The selective advantage of cytoplasmic incompatibility often results in a population sweep of Wolbachia and co-transmitted mitochondrial genomes. Mitochondrial evolution and phylogenetic inferences drawn from mitochondrial gene sequences are thus potentially compromised by reproductive manipulating symbionts, like Wolbachia. Our initial analyses of phylogenetic patterns among collected Wolbachia-infected and uninfected mosquito species suggested significant Wolbachia-induced effects on mitochondrial evolutionary patterns. Discordant mitochondrial and nuclear phylogenies among Aedes and Culex species were associated with infections status, with a distinct mitochondrial clade of infected Aedes and Culex species, separate from uninfected species of the genera. Statistical analyses of molecular substitution among infected and uninfected sequence samples revealed elevated rates of substitution for the mitochondrial sequences of the discordant infected Aedes/Culex clade. Subsequent phylogenetic analyses suggested that the observed discordance could be attributed to long-branch attraction effects associated with elevated rates of substitution. Our results highlight the impact cytoplasmic selection can have on phylogenetic inference in limited sample sets with Wolbachia-infected and uninfected species.


We thank professors Wendy Dustman, Rebekah Ward, Fengjie Sun, and the Lawrenceville Science Tavern for useful discussion on research results.