Bird species (Charadriiformes) does not impact endosymbiotic bacteria (Gammaproteobacteria) of their ectoparasites (Insecta: Phthiraptera: Ischnocera)

Endosymbiotic bacteria of insects can facilitate host expansion into novel niches by providing their host with a fitness benefit such as vitamins or amino acids that are otherwise lacking in their hosts' diet. This close association can lead to cospeciation between insects and their symbionts; however, the symbionts’ small genome size leaves it susceptible to genome derogation which can result in symbiont replacement. Here, we screen chewing lice infesting shorebirds and terns to see what endosymbiotic bacteria are present, and build a summary phylogeny that includes louse endosymbiont sequences from this study as well as those from other louse genera, insects and bacteria strains from GenBank. We found a Sodalis-allied endosymbiont in Carduiceps, Lunaceps, Quadraceps, and Saemundssonia, as well as symbionts belonging to the family Enterobacteriaceae in Lunaceps, and Quadraceps. No louse species were host to both endosymbionts; however, the birds Kentish Plover (Charadrius alexandrinus) and Greater Crested Tern (Thalasseus bergii) were host to two genera of lice, each of which was infested with a different group of endosymbionts. In the summary phylogeny the endosymbionts from shorebirds, and tern lice did not form a monophyletic group, and therefore likely acquired their bacterial endosymbionts multiple times.