The ants are a diverse and abundant group of insects, numbering in excess of 12,000 species and comprising a greater biomass than most land-dwelling animals. When combined with their roles as predators, scavengers, and defenders of plants and insects, it is clear that these organisms are among the more influential animals found within terrestrial ecosystems. Although they are often thought of as carnivores, the ants have evolved to utilize a wide range of diets. Notably, several groups have come to feed at the base of the food chain, relying on low-quality, herbivorous diets that provide insufficient nutritional sustenance. While it is not known just how these insects can persist on such diets, symbiotic bacteria are hypothesized to play a central role. This research project will test this hypothesis, and investigate the roles of nutritional gut bacteria in the evolution of ant diets. Using molecular phylogenetics, the evolutionary relationships among ants from several geographic locations will be determined. Stable isotopes will be used to characterize the feeding positions of these species on the food chain, and DNA sequencing will be used to determine composition of their bacterial gut communities. These results will be combined to test whether ants feeding on low-quality diets have co-evolved with specialized, beneficial gut bacteria, and whether habitat disturbance or introductions of invasive ants have changed these dynamics. This synthetic approach will not only reveal features shaping bacterial communities from animal hosts, it will also determine whether symbiotic bacteria have played important roles in the evolution of ant diets, enabling the origins of novel lifestyles and proliferation within otherwise inhospitable habitats.
By examining native and invasive species from pristine and disturbed habitats, this work will reveal how environmental changes can alter interactions between animals and their gut microbes. Such work is broadly important to understanding the adaptability of animal species, for example, in dealing with climate change. This project will support the training of a postdoctoral scholar, graduate and undergraduates in interdisciplinary research, and provide opportunities for public involvement in the research through the Chicago Field Museum of Natural History.
Many animals rely on gut-associated microbes to up-regulate their diets, but the extent of this interaction is not well known for many groups. Among the ants, a social animal group, species range in their diets from predators to generalists to herbivores. We explored the diversity of gut-associated bacteria among these different feeding strategies and across developmental stages to understand the functional role of these microbes. We also sampled multiple life stages and locations to determine whether bacteria are acquired from the environment or are stable long-term members of the gut community. To determine if diets shape gut-community diversity and abundance we conducted diet manipulation experiments. We found that ants have diverse gut bacterial communities and that herbivorous species have stable and often co-evolved gut microbes. By sampling across diverse geographic regions we show that ants do not acquire their gut flora from the environment, but that gut community diversity and more often abundance is influenced by life stage and overall diet preference. We also find that diet can influence gut community abundance in predictable ways suggesting important functional roles. These findings have implications for understanding more generally what importance and role gut-associated bacteria have in animals and how social species may maintain and spread these microbes.
