Figure 2: Bacterial symbiosis across the tree of life.

A phylogeny of bacterial symbionts in our database built using an ∼1,500 bp region of the 16S rRNA gene, with images of their host groups. Vertically transmitted symbionts are shown with red circles and horizontally transmitted symbionts are shown with black circles. Multiple species names at the tips are distinct lineages found in different host groups. Images of hosts are not intended to be exact representations of the host species, but more of the general host group (for example, wasp, worm and plant). Where there is no image, this is because a suitable representation of the host species was not available. Host images sourced from Phylopic (phylopic.org): Graphocephala coccinea courtesy of Melissa Broussard; Hippoboscoidea fly courtesy of Gareth Monger; Sepioidea squid courtesy of David Sim and T. Michael Keesey; Uropodina tick courtesy of Birgit Lang; and Brugia nematode courtesy of Gareth Monger; all available under a Creative Commons license.