The Microbiotas Response to Host Adaptive Evolution

Over the past two decades, experimental evolution has significantly advanced our understanding of evolutionary patterns and mechanisms of genomic change. One critically underexplored dimension is the role of microbiota in host adaptive evolution. In this research we investigate the microbiota from forty laboratory-selected Drosophila melanogaster populations exhibiting four distinct aging trajectories, ranging from extremely-short lifespans to -long lifespans. Using metagenomic sequencing and colony forming unit (CFU) counts in both conventional and gnotobiotic conditions, we uncover substantial microbiota differentiation among these populations. The most striking pattern is the consistent loss of Wolbachia in populations selected for rapid aging, in contrast to its near complete dominance in long-lived populations. This suggests a positive association between relative abundance of Wolbachia and lifespan, alongside a negative correlation between Wolbachia and Acetic Acid Bacteria (AAB) titres. These findings position the microbiota, and particularly Wolbachia, as a potentially integral component in host life history evolution, with implications for understanding the microbial contributions to aging and adaptation. SignificanceFruit flies bred for short lifespans consistently lose the bacterial symbiote Wolbachia, while the microbiota of long-lived flies are almost entirely dominated by it. There is a stable, recurring link between this microbe and lifespan, and traits associated with lifespan. This persistent pattern suggests that microbiota, Wolbachia in particular, may play a direct role in shaping the evolution of lifespan.