Gut microbiome communities vary across translocated populations of the Seychelles warbler

Conservation translocations are an increasingly common tool used to help combat species extinction and global biodiversity loss. However, their success is dependent on a wide range of abiotic and biotic factors. To date, the potential role of host-associated microbiomes in translocation success has been overlooked despite their fundamental contribution to host health and fitness. Here, we use faecal samples to evaluate how gut microbiome communities vary across the last remnant (source) population, and all four translocated populations (established between 1988 and 2011), of the Seychelles warbler (Acrocephalus sechellensis). Gut microbiome alpha diversity was lower in all translocated populations compared to the source population on Cousin Island. Gut microbiome composition also varied, with several short-chain fatty acid producing bacterial families being lost from the core microbiome in some translocated populations; such taxa have been shown to play an important role in maintaining host metabolic health. Furthermore, the two translocated populations that were established the longest time ago, and with the fewest individuals, had reduced inter-individual gut microbiome variability compared to the source population. While it was not possible to directly assess the specific drivers of these differences due to samples being collected after the translocation event, it is likely that the size of the founding population, subsequent loss of host genetic variation and environmental factors all contribute to shaping gut microbiome variation amongst these populations. Future work should assess whether taxonomic variation translates into differences in gut microbiome function and the possible consequences for host population health and long-term resilience to environmental change.