The role of host phylogeny varies in shaping microbial diversity in the hindguts of lower termites.

The hindguts of lower termites and Cryptocercus cockroaches are home to a distinct community of archaea, bacteria, and protists (primarily parabasalids and some oxymonads). Within a host species, the composition of these hindgut communities appears relatively stable, but the evolutionary and ecological factors structuring community composition and stability are poorly understood, as are differential impacts of these factors on protists, bacteria, and archaea. We analyzed the microbial composition of parabasalids and bacteria in the hindguts of Cryptocercus punctulatus and 23 species spanning 4 families of lower termites by pyrosequencing variable regions of the small-subunit rRNA gene. Especially for the parabasalids, these data revealed undiscovered taxa and provided a phylogenetic basis for a more accurate understanding of diversity, diversification, and community composition. The composition of the parabasalid communities was found to be strongly structured by the phylogeny of their hosts, indicating the importance of historical effects, although exceptions were also identified. Particularly, spirotrichonymphids and trichonymphids likely were transferred between host lineages. In contrast, host phylogeny was not sufficient to explain the majority of bacterial community composition, but the compositions of the Bacteroidetes, Elusimicrobia, Tenericutes, Spirochaetes, and Synergistes were structured by host phylogeny perhaps due to their symbiotic associations with protists. All together, historical effects probably resulting from vertical inheritance have had a prominent role in structuring the hindgut communities, especially of the parabasalids, but dispersal and environmental acquisition have played a larger role in community composition than previously expected.