Collaborative Research: Inferring bacterial roles in the evolution of trophic level across the ants

蚂蚁是一种种类繁多的昆虫，数量超过12000种，其生物量比大多数陆生动物都要大。当结合它们作为捕食者、食腐者和植物和昆虫的捍卫者的角色时，很明显，这些生物是在陆地生态系统中发现的更有影响力的动物。虽然它们通常被认为是食肉动物，但蚂蚁已经进化到可以利用各种各样的食物。值得注意的是，有几个群体已经开始在食物链的底部觅食，依靠低质量的草食性饮食，这些饮食提供的营养不足。虽然尚不清楚这些昆虫是如何坚持这样的饮食的，但共生细菌被假设起着核心作用。本研究项目将验证这一假设，并研究营养肠道细菌在蚂蚁饮食进化中的作用。利用分子系统遗传学，将确定几个地理位置的蚂蚁之间的进化关系。稳定同位素将用于表征这些物种在食物链上的摄食位置，DNA测序将用于确定其肠道细菌群落的组成。这些结果将结合起来测试以低质量食物为食的蚂蚁是否与专门的有益肠道细菌共同进化，以及栖息地干扰或入侵蚂蚁的引入是否改变了这些动态。这种综合方法不仅将揭示动物宿主形成细菌群落的特征，还将确定共生细菌是否在蚂蚁饮食的进化中发挥了重要作用，使新的生活方式的起源成为可能，并在其他不适宜居住的栖息地中繁殖。通过研究来自原始和受干扰栖息地的本地和入侵物种，这项工作将揭示环境变化如何改变动物与其肠道微生物之间的相互作用。这样的工作对于理解动物物种的适应性非常重要，例如在应对气候变化方面。该项目将支持培养跨学科研究的博士后学者、研究生和本科生，并通过芝加哥菲尔德自然历史博物馆为公众参与研究提供机会。

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.