Data from: Dietary specialization in mutualistic acacia-ants affects relative abundance but not identity of host-associated bacteria

Acacia-ant mutualists in the genus Pseudomyrmex nest obligately in acacia
plants and, as we show through stable isotope analysis, feed at a
remarkably low trophic level. Insects with diets such as these sometimes
depend on bacterial symbionts for nutritional enrichment. We, therefore,
examine the bacterial communities associated with acacia-ants in order to
determine whether they host bacterial partners likely to contribute to
their nutrition. Despite large differences in trophic position,
acacia-ants and related species with generalized diets do not host
distinct bacterial taxa. However, we find that a small number of
previously undescribed bacterial taxa do differ in relative abundance
between acacia-ants and generalists, including several Acetobacteraceae
and Nocardiaceae lineages related to common insect-associates. Comparisons
with an herbivorous generalist, a parasite that feeds on acacias, and a
mutualistic species with a generalized diet show that trophic level is
likely responsible for these small differences in bacterial community
structure. While we did not experimentally test for a nutritional benefit
to hosts of these bacterial lineages, metagenomic analysis reveals a
Bartonella relative with an intact nitrogen-recycling pathway widespread
across Pseudomyrmex mutualists and generalists. This taxon may be
contributing to nitrogen enrichment of its ant hosts through urease
activity and, concordant with an obligately host-associated lifestyle,
appears to be experiencing genome-wide relaxed selection. The lack of
distinctiveness in bacterial communities across trophic level in this
group of ants shows a remarkable ability to adjust to varied diets,
possibly with assistance from these diverse ant-specific bacterial
lineages.