Evidence from the gut microbiota of swarming alates of a vertical transmission of the bacterial symbionts in Nasutitermes arborum (Termitidae, Nasutitermitinae)

Studies on termite symbiosis haverevealed that significant symbiont lineages are maintainedacross generations. However, most studies havefocused only on the worker caste. Little is knownabout the gut microbiota of reproductives, the mostprobable vectors for transmitting these lineages tooffspring. Using 16S rRNA gene-based IlluminaMiSeq sequencing, we compared the gut microbiotaof swarming alates of the higher termite Nasutitermesarborum with those of their nestmates from theparental colony. The OTU-based alpha diversityindices showed that the gut microbiota of the alateswas at least as diverse as those of non-reproductiveadults. It was largely dominated by Spirochaetesmostly of the Treponema I cluster (63.1% of reads),the same dominant taxa found in soldiers and workersof this species and in workers of closely relatedNasutitermes species. The termite-specific lineagesalso included other representative taxa such as severalclusters of Bacteroidetes and Fibrobacteres-TG3group. The microbiota of alates was dominated by acore set of host-specific lineages (87% of reads, 77.6%of OTUs), which were always present across all castes/stages. This first comprehensive survey of the microbiotaof the founding reproductives of these xylophagoushigher termites shows that the bulk of the hostendogenous symbionts, mostly taxa that cannot thriveoutside the gut, are brought from the parent colony.The royal pair therefore seems to be a key player in thetransmission of symbionts across generations andthereby in host-symbiont codiversification. The highproportion of fiber-degrading lineages in their gutsuggests a wood-rich diet unlike the larval stages