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Dryad

A time-lagged association between the gut microbiome, nestling weight and nestling survival in wild great tits

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Nov 30, 2020 version files 71.29 KB

Abstract

  1. Natal body mass is a key predictor of viability and fitness in many animals. While variation in body mass and therefore viability of juveniles may be explained by genetic and environmental factors, emerging evidence points to the gut microbiota as an important factor influencing host health. The gut microbiota is known to change during development, but it remains unclear whether the microbiome predicts fitness, and if it does, at which developmental stage it affects fitness traits.
  2. We collected data on two traits associated with fitness in wild nestling great tits (Parus major): weight and survival to fledging. We characterised the gut microbiome using 16S rRNA sequencing from nestling faeces and investigated temporal associations between the gut microbiome and fitness traits across development at day 8 (D8) and day 15 (D15) post-hatching. We also explored whether particular microbial taxa were ‘indicator species’ that reflected whether nestlings survived or not.
  3. There was no link between mass and microbial diversity on D8 or D15. However, we detected a time-lagged relationship whereby the microbial diversity at D8 was negatively associated with weight at D15, while controlling for weight at D8. Indicator species analysis revealed that while several taxa were unique to birds that either survived or did not survive, there were no universal taxa that were consistently found across all birds within either survival group. This suggests that the presence of particular bacterial taxa may be sufficient, but not necessary for determining future survival, perhaps owing to functional overlap in microbiota.
  4. We highlight that measuring microbiome-fitness relationships at just one time point may be misleading, especially early in life. Instead, microbial-host fitness effects should be investigated longitudinally as there may be critical development windows in which key microbiota are established and prime host traits associated with nestling weight. Pinpointing which features of the gut microbial community impact on host fitness, and when during development this occurs, will shed light on population level processes and has the potential to support conservation.