Are ecological communities the seat of endosymbiont horizontal transfer and diversification? A case study with soil arthropod community

Background/Question/Methods

Maternally inherited endosymbionts are one of the most abundant bacteria infecting arthropods and show extensive horizontal transfer. Such widespread distribution and extensive recombination among these endosymbionts could be an outcome of horizontal transfer as for such genetic exchanges to occur their hosts should come in contact. One such level of biological organization where different hosts can do that is the ecological community. Despite various studies focusing on known model species and specific ecological interactions among hosts, reports on community wide endosymbiont data are rare. To better understand endosymbiont spread, we investigated the incidence, diversity, extent of horizontal transfer and recombination of three such endosymbionts (Wolbachia, Cardinium and Arsenophonus) in a specific soil arthropod community. Wolbachia strain characterization was done using multiple genes whereas single 16S rRNA gene was used for Cardinium and Arsenophonus.

Results/Conclusions

Amongst 3509 individual host arthropods belonging to 390 morphospecies, 12.05% were infected with Wolbachia, 2.82% with Cardinium and 2.05% with Arsenophonus. Phylogenetic incongruence between host and endosymbiont indicated extensive horizontal transfer of endosymbionts within this community. Three cases of recombination between Wolbachia supergroups and eight incidences of within supergroup genetic exchange were also found. Statistical tests of similarity indicated supergroup A Wolbachia and Cardinium to show a pattern consistent with rapid horizontal transfer within the community. However same tests done for super group B Wolbachia and Arsenophonus did not show similar patterns. We highlight the importance of extensive community wide studies for a better understanding of the spread of endosymbionts across global arthropod communities.