Ongoing Coevolution of Wolbachia and a Widespread Invasive Ant, Anoplolepis gracilipes

Abstract

While <i>Wolbachia</i> are commonly found among arthropods, intraspecific infection rates can vary substantially across the geographic populations. Here we report nearly 100% prevalence of <i>Wolbachia</i> in the global populations of the yellow crazy ant, <i>Anoplolepis gracilipes</i>. To understand coevolutionary history between <i>Wolbachia</i> and <i>A. gracilipes</i>, we identified single nucleotide polymorphisms (SNPs) in <i>Wolbachia</i> from the ant across 12 geographical regions and compared the phylogeny of SNP-based <i>Wolbachia</i> to patterns of the ant's mitochondrial DNA (mtDNA) variation. Our results revealed a strong concordance between phylogenies of <i>Wolbachia</i> and host mtDNA, providing immediate evidence of co-divergence. Among eight identified SNP loci separating the genetic clusters of <i>Wolbachia</i>, seven loci are located in potential protein-coding genes, three of which being non-synonymous SNPs that may influence gene functions. We found a <i>Wolbachia</i> hypothetical protein gene with signature of positive selection. These findings jointly allow us to characterize <i>Wolbachia</i>-ant coevolution and also raise a question about mechanism(s) underlying maintenance of high prevalence of <i>Wolbachia</i> during the colonization of this invasive ant.