Faecal inoculations alter the gastrointestinal microbiome and allow dietary expansion in a wild specialist herbivore, the koala

Michaela D J Blyton,William Foley,Rochelle M Soo,Ben D Moore,Desley Whisson,Jack Pascoe,Karen J Marsh,Mark Le Pla,Philip Hugenholtz

doi:10.1186/s42523-019-0008-0

Abstract

BackgroundDifferences between individuals in their gastrointestinal microbiomes can lead to variation in their ability to persist on particular diets. Koalas are dietary specialists, feeding almost exclusively on Eucalyptus foliage but many individuals will not feed on particular Eucalyptus species that are adequate food for other individuals, even when facing starvation. We undertook a faecal inoculation experiment to test whether a koala’s gastrointestinal (GI) microbiome influences their diet. Wild-caught koalas that initially fed on the preferred manna gum (Eucalyptus viminalis) were brought into captivity and orally inoculated with encapsulated material derived from faeces from koalas feeding on either the less preferred messmate (E. obliqua; treatment) or manna gum (control).ResultsThe gastrointestinal microbiomes of wild koalas feeding primarily on manna gum were distinct from those feeding primarily on messmate. We found that the gastrointestinal microbiomes of koalas were unresponsive to dietary changes because the control koalas’ GI microbiomes did not change even when the nocturnal koalas were fed exclusively on messmate overnight. We showed that faecal inoculations can assist the GI microbiomes of koalas to change as the treatment koalas’ GI microbiomes became more similar to those of wild koalas feeding on messmate. There was no overall difference between the control and treatment koalas in the quantity of messmate they consumed. However, the greater the change in the koalas’ GI microbiomes, the more messmate they consumed after the inoculations had established.ConclusionsThe results suggest that dietary changes can only lead to changes in the GI microbiomes of koalas if the appropriate microbial species are present, and/or that the koala gastrointestinal microbiome influences diet selection.

Highlights

Differences between individuals in their gastrointestinal microbiomes can lead to variation in their ability to persist on particular diets
The GI microbiomes of koalas feeding on messmate or manna gum Our results confirm the previous findings of Brice and colleagues [21] that showed that the GI microbiomes of koalas feeding on messmate differ from those of koalas feeding on manna gum based on 16 s rRNA profiles (PERMANOVA: F = 15.378, p < 0.001, R2 = 0.49)
The GI microbiomes of koalas found in manna gum forest in this study were found to separate from those of koalas found in messmate forest on dimension 1 (PC1) of the principal components analysis (t = − 5.288, p < 0.001; Fig. 1)

Summary

Introduction

Differences between individuals in their gastrointestinal microbiomes can lead to variation in their ability to persist on particular diets. In addition to constraints imposed by factors such as food availability, social structure and life history, an animal’s diet may be restricted if they do not possess an appropriate microbial assemblage. Such dietary niche restriction could have important ramifications for a species’ persistence in (2019) 1:6 different habitats. The capacity for an animal’s GI microbiome to adapt to changes in the host’s diet may affect conservation initiatives including translocations and captive breeding, where animals may be faced with a sudden change in diet. There can be wide benefits from gaining an understanding of the conditions under which the GI microbiome can or cannot adapt to host diet and how such adaptation impacts the host

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