Termite-Like Phylogenetic Conservation of Gut Microbiota in Passalid Beetles Suggests Evolutionary Convergence in Decaying Wood Degradation
Beetles of the family Passalidae are an important group of subsocial wood-decomposing (saproxylophagous) insects, spending their entire life cycle living inside and feeding on rotten logs. Decaying wood is an abundant resource, but nutritionally poor and challenging to digest. As in other saproxylophagous insects, digestion for passalids is only possible through symbiotic relationships with their…
The Passalid beetles, a type of subsocial wood-decomposing insect, spend their entire lives inside and feed on rotten logs. These beetles depend on symbiotic relationships with their gut microbiota to properly digest decaying wood, which is nutritionally poor and challenging to break down. Although this symbiotic relationship is crucial, it is not well understood, making it difficult to determine the factors influencing this association and its role in Passalidae's evolution.
To better comprehend this relationship, researchers conducted a study using high-throughput sequencing of the microbial 16S rRNA gene to examine the composition and abundance of symbiont lineages in the hindguts of passalid beetles from two mountain systems in the Colombian Caribbean. They analyzed the impact of geographic proximity and phylogenetic relationship on gut microbial composition and structure.
The findings suggest that phylogenetic relatedness plays a more significant role in shaping the gut microbiome of passalid beetles than geographical proximity. Specifically, congeneric species, which are closely related in terms of their evolutionary history, exhibited more similar microbiomes than sympatric species, which share the same locality.
Moreover, the bacterial and archaeal communities showed signs of phylosymbiosis, with bacterial communities reflecting relationships mainly among genus-level clades, and archaeal communities maintaining congruence mainly at deeper host lineages. Lastly, researchers identified a significant amount of bacterial taxonomic novelty, with nearly half of the bacterial reads remaining unclassified at the genus level, indicating a large amount of undiscovered microbial diversity associated with Passalidae.
These results position Passalidae as a valuable model for investigating the evolutionary processes that govern gut microbiome assembly and the evolution of lignocellulose-feeding symbioses.
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