Supergroup F in terrestrial isopods: Horizontal transmission from termites?

Unlabelled: Horizontal transmission between distantly related species has been used to explain how infect multiple species at astonishing rates despite the selection for resistance. Recently, a terrestrial isopod species was found to be infected by an unusual strain of supergroup F . However, only of supergroup B is typically found in isopods. One possibility is that these isopods acquired the infection because of their recurrent contact with termites-a group with strong evidence of infection by supergroup F . Thus, our goals were: (1) check if the infection was an isolated case in isopods, or if it revealed a broader pattern; (2) search for infection in the termites within Brazil; and (3) look for evidence consistent with horizontal transmission between isopods and termites. We collected terrestrial isopods and termites along the Brazilian coastal Atlantic forest. We sequenced and identified the strains found in these groups using , , and genes. We constructed phylogenies for both bacteria and host taxa and tested for coevolution. We found the supergroup F in other species and populations of , and also in and termites. The phylogenies showed that, despite the phylogenetic distance between isopods and termites, the strains clustered together. Furthermore, cophylogenetic analyses showed significant jumps of between terrestrial isopods and termites. Thus, our study suggests that the horizontal transmission of supergroup F between termites and terrestrial isopods is likely. Our study also helps understanding the success and worldwide distribution of this symbiont.

Supplementary Information: The online version of this article (10.1007/s10682-021-10101-4) contains supplementary material, which is available to authorized users.