Vertebrate bacterial gut diversity: size also matters

Abstract

Background: One of the central issues in microbial ecology is to understand the parameters that drive diversity. Among these parameters, size has often been considered to be the main driver in many different ecosystems. Surprisingly, the influence of size on gut microbial diversity has not yet been investigated, and so far in studies reported in the literature only the influences of age, diet, phylogeny and digestive tract structures have been considered. This study explicitly challenges the underexplored relationship connecting gut volume and bacterial diversity.

Results: The bacterial diversity of 189 faeces produced by 71 vertebrate species covering a body mass range of 5.6 log. The animals comprised mammals, birds and reptiles. The diversity was evaluated based on the Simpson Diversity Index extracted from 16S rDNA gene fingerprinting patterns. Diversity presented an increase along with animal body mass following a power law with a slope z of 0.338 ± 0.027, whatever the age, phylogeny, diet or digestive tract structure.

Conclusions: The results presented here suggest that gut volume cannot be neglected as a major driver of gut microbial diversity. The characteristics of the gut microbiota follow general principles of biogeography that arise in many ecological systems.

Keywords: Biodiversity; Biogeography; Fingerprint; Gut; Species-area relationship.

Fig. 1

Relationship between the animal body mass and the Simpson Diversity Index for gut microbiota. Diamonds, circles and triangles correspond to birds, mammals and reptiles, respectively. Small, medium and large sizes correspond to 1, 2–5, >10 individuals, respectively. Green, brown, grey, red, blue and yellow colors correspond to herbivorous, granivorous, omnivorous, carnivorous, piscivorous and frugivorous diets, respectively. Bold fonts make reference to the animals mentioned in the text