Contrasted specificity of gut and endosymbiont bacterial communities in alpine grasshoppers and crickets

Bacteria colonize the body of macro-organisms to form associations ranging from parasitic to beneficial. Endosymbiont and gut symbiont community compositions are influenced by host ecology (e.g., diet) and host evolution. In contrast to horizontally acquired symbionts (e.g., some gut symbionts), we expect the microbiota structure of vertically inherited symbionts (e.g., endosymbionts like Wolbachia) to be strongly associated with the host phylogeny, i.e., harbor “phylosymbiosis”. Here, using metabarcoding and qPCR on 336 guts from 24 orthopteran species (grasshoppers and crickets) in the Alps, we observed that microbiota harbored specificity at the scale of host species, i.e., hosts from the same species had more similar microbiota than hosts from different species. Elevation correlated with microbiome composition, but we did not recover phylosymbiosis: closely related host species did not harbor more similar microbiota than distantly related species. Our findings indicate that, contrary to mammals, gut microbiota of orthopteran is rather structured by host identity and habitat than by the host phylogeny. The higher specificity in endosymbionts corroborates the idea that vertically transmitted microbes harbor stronger specificity signal, but the absence of phylosymbiosis suggests that specificity disappears on evolutionary time scales.