Résumé
Mammals have diversified into many dietary niches. Specialized
myrmecophagous (ant- and termite-eating) placental mammals represent a
textbook example of evolutionary convergence driven by extreme diet
specialization. Armadillos, anteaters, aardvarks, pangolins and aardwolves
thus provide a model system for understanding the potential role of gut
microbiota in the convergent adaptation to myrmecophagy. Here, we expand
upon previous mammalian gut microbiome studies by using high-throughput
barcoded Illumina sequencing of the 16S rRNA gene to characterize the
composition of gut microbiota in 15 species representing all placental
myrmecophagous lineages and their close relatives from zoo- and
field-collected samples. We confirm that both diet and phylogeny drive the
evolution of mammalian gut microbiota, with cases of convergence in global
composition, but also examples of phylogenetic inertia. Our results reveal
specialized placental myrmecophages as a spectacular case of large-scale
convergence in gut microbiome composition. Indeed, neighbour-net networks
and beta-diversity plots based on UniFrac distances show significant
clustering of myrmecophagous species (anteaters, aardvarks and
aardwolves), even though they belong to phylogenetically distant lineages
representing different orders. The aardwolf, which diverged from
carnivorous hyenas only in the last 10 million years, experienced a
convergent shift in the composition of its gut microbiome to become more
similar to other myrmecophages. These results confirm diet adaptation to
be a major driving factor of convergence in gut microbiome composition
over evolutionary timescales. This study sets the scene for future
metagenomic studies aiming at evaluating potential convergence in
functional gene content in the microbiomes of specialized mammalian
myrmecophages.