Gut microbiome composition, not alpha diversity, is associated with survival in a natural vertebrate population

Abstract

Background The vertebrate gut microbiome (GM) can vary substantially across individuals within the same natural population. Although there is evidence linking the GM to health in captive animals, very little is known about the consequences of GM variation for host fitness in the wild. Here, we explore the relationship between faecal microbiome diversity, body condition, and survival using data from the long-term study of a discrete natural population of the Seychelles warbler (Acrocephalus sechellensis) on Cousin Island. To our knowledge, this is the first time that GM differences associated with survival have been fully characterised for a natural vertebrate species, across multiple age groups and breeding seasons. Results We identified substantial variation in GM community structure among sampled individuals, which was partially explained by breeding season (5% of the variance), and host age class (up to 1% of the variance). We also identified significant differences in GM community membership between adult birds that survived, versus those that had died by the following breeding season. Individuals that died carried increased abundances of taxa that are known to be opportunistic pathogens, including several ASVs in the genus Mycobacterium. However, there was no association between GM alpha diversity (the diversity of bacterial taxa within a sample) and survival to the next breeding season, or with individual body condition. Additionally, we found no association between GM community membership and individual body condition. Conclusions These results demonstrate that components of the vertebrate GM can be associated with host fitness in the wild. However, further research is needed to establish whether changes in bacterial abundance contribute to, or are only correlated with, differential survival; this will add to our understanding of the importance of the GM in the evolution of host species living in natural populations.

Linking migration and microbiota at a major stopover site in a long-distance avian migrant

“…Previous studies have shown that physiological stress can decrease microbial diversity [ 21 ] and both stress and poor body conditions have been connected to microbial dysbiosis [ 15 , 22 ]. Changes in microbial diversity and community dysbiosis have also been associated with lower survival rates [ 23 – 26 ]. Further, although age- and sex-related variation in microbiota composition is commonly reported for birds (e.g., [ 14 , 24 , 27 , 28 ]), details about such effects are still missing in the context of bird migration.…”

Aging gut microbiota of wild macaques are equally diverse, less stable, but progressively personalized

“…This is necessary to identify plausible drivers (e.g., tooth wear, immunosenescence) and fitness consequences (e.g., muscle loss, declining energy balance constraining fertility) of age-related changes in gut bacterial composition. The possibility that gut bacterial composition exhibits terminal senescence [ 80 ], independent of age, has not been investigated in this or previous studies on mammals due to lack of data on individual survival and remains open…”

Evolved high aerobic capacity has context-specific effects on gut microbiota

“…Finally, as not all offspring survived to the end of the experiment, the results may also be affected by selective mortality. Differential abundance of gut bacteria has been linked with survival (Akbar et al, 2021;Worsley et al, 2021). If gut microbiota affected the survival of young voles, then only the voles with the most appropriate microbiota (e.g., matching the evolved metabolic needs) would have been sampled.…”