LAUSR

Bacterial symbioses play important roles in shaping diverse biological processes in nematodes, and serve as targets in nematode biocontrol strategies. Focusing on the Xiphinema americanum species complex, we expanded upon recent research investigating patterns of coevolution between Xiphinema spp. and Xiphinematobacter spp., utilising two symbiont genetic markers of varying evolutionary rates. Phylogenetic analysis of nematode mitochondrial DNA (mtDNA) revealed five strongly supported major clades. Analysis of slow-evolving 16S rDNA in bacterial symbionts resulted in a phylogenetic topology composed of four major clades that grouped taxa highly congruent with the nematode mtDNA topology. A faster evolving protein-coding symbiont gene (nad) provided more phylogenetic resolution with seven well-supported clades, also congruent with the nematode mtDNA tree topology. Our results reinforce recent studies suggesting extensive coevolution between Xiphinema spp. and their vertically transmitted endosymbionts Xiphinematobacter spp. and illustrate the advantages of including genetic markers of varying evolutionary rates in coevolutionary and phylogenetic studies.