Evolutionary origins of ψND5 elements. Intraspecific phylogeny of C. briggsae natural isolates based on neighbor-joining analysis of mtDNA sequences is shown. Neighbor-joining and maximum parsimony analyses of nearly complete mtDNA sequences yielded trees with identical topologies. GL indicates the global intraspecific C. briggsae superclade; KE indicates the Kenya clade; TE and TR indicate the temperate and tropical subclades of GL, respectively. Bootstrap support of 100% for both analysis approaches was observed for all selected nodes indicated by asterisks – for the node supporting monophyly of C. briggsae and Caenorhabditis sp. n. 5, neighbor-joining values are on top of maximum parsimony values. The scale bar represents 0.01 substitutions per site. Bolts indicate branches where ψND5 elements are predicted to have originated based on the phylogeny and the presence of ψND5-1 and ψND5-2 in specific Caenorhabditis species and strains. The distributions of isolates into temperate and tropical clades in our analyses were consistent with their distributions based on previous analyses of nuclear loci .
Howe and Denver BMC Evolutionary Biology 2008 8:62 doi:10.1186/1471-2148-8-62