Nest composition, stable isotope ratios and microbiota unravel the feeding behaviour of an inquiline termite

Termites are eusocial insects having evolved several feeding, nesting and reproductive strategies. Among them, inquiline termites live in a nest built by other termite species: some of them do not forage outside the nest, but feed on food stored by the host or on the nest material itself. In this study, we characterized some dimensions of the ecological niche of Cavitermes tuberosus (Termitidae: Termitinae), a broad-spectrum inquiline termite with a large neotropical distribution, to explain its ecological success. We used an integrative framework combining ecological measures (physico-chemical parameters, stable isotopic ratios of N and C) and Illumina MiSeq sequencing of 16S rRNA gene to identify bacterial communities and to analyse termites as well as the material from nests constructed by different termite hosts (the builders). Our results show that (1) nests inhabited by C. tuberosus display a different physico-chemical composition when compared to nests inhabited by its builder alone; (2) stable isotopic ratios suggest that C. tuberosus feeds on already processed, more humified, nest organic matter; and (3) the gut microbiomes cluster by termite species, with the one of C. tuberosus being much more diverse and highly similar to the one of its main host, Labiotermes labralis. These results support the hypothesis that C. tuberosus is a generalist nest feeder adapted to colonize nests built by various builders, and explain its ecological success.