Lemur gut microeukaryotic community variation is not associated with host phylogeny, diet, or habitat

Identifying the major forces driving variation in gut microbiomes enhances our understanding of how and why symbioses between hosts and microbes evolved. Gut prokaryotic community variation is often closely associated with host evolutionary and ecological variables. Whether these same factors drive variation in other microbial taxa occupying the animal gut remains largely untested. Here, we present a one-to-one comparison of gut prokaryotic (16S rRNA metabarcoding) and microeukaryotic (18S rRNA metabarcoding) community patterning among 12 species of wild lemurs. Lemurs were sampled from dry forests and rainforests of southeastern Madagascar and display a range of phylogenetic and ecological niche diversity. We found that while lemur gut prokaryotic community diversity and composition vary with host taxonomy, diet, and habitat, gut microeukaryotic communities have no detectable association with any of these factors. We conclude that gut microeukaryotic community composition is largely random, while gut prokaryotic communities are conserved among host species. As a possible mechanism explaining these patterns, we suggest purifying selection purges microbes with negative and commensal host associations while positive selection promotes the persistence of beneficial microbes. It is therefore likely that a greater proportion of gut microeukaryotic communities comprise taxa with commensal, transient, and/or parasitic symbioses compared with gut prokaryotes, many of which form long-term relationships with the host and perform important biological functions.